IC-NRLF 315 3Mfl STEEL LIBRARY OF THE UNIVERSITY OF CALIFORNIA. Class IRON, STEEL, AND FIREPROOF CONSTRUCTION RICHARD MORELAND & SON, Ltd. Engineers, 80, GOSWELL ROAD, LONDON. \ Manufacturers of SOLID WROUGBf^ STEEL COLUMNS (With Wrought Steel Caps and Bases), WROUGHT STEEL f TANCHIONS, GIRDERS, JOISTS, ROOFWORK. All classes of Steel Constructional Work can be manufactured at once from Stock. ESTIMATES AND DESIGNS FREE ON APPLICATION, IRON, STEEL, AND FIRE PROOF CONSTRUCTION WITH NUMEROUS ENGRAVINGS AND DIAGRAMS EDITED BY PAUL 1ST. HASLUCK ' \ HONOURS MEDALLIST IN TECHNOLOGY EDITOR OF "WORR 1 " AND "BUILDING WORLD" AUTHOR OK "HANDYBOOKS FOR HANDICRAFTS," ETC. ETC. OF THE UNIVERSITY OF CASSELL AND COMPANY, LIMITED LONDON, PARIS, NEW YORK % MELBOURNE. MCMVI ALL RIGHTS RESERVED PREFACE. IRON, STEEL, AND FIREPROOF CONSTRUCTION contains, in a form convenient for everyday use, a comprehensive digest of infor- mation, contributed to the columns of BUILDING WORLD, one of the weekly journals it is my fortune to edit, and supplies concise information on the general principles and practice of the art on which it treats. In preparing 'for publication in book form the mass of relevant matter contained in the volumes of BUILDING WORLD, much of it necessarily had to be rearranged and re-written. From this cause the writings of several contributors are blended, but it may be said that the greater part of the book consists of articles written by Mr. S. G. N. Mann. Headers who may desire additional information respecting special details of the matters dealt with in this book, or in- struction on any building trade subjects, should address a question to the Editor of BUILDING WORLD, La Belle Sauvage, London, E.G., so that it may be answered in the columns of that journal. P. N. HASLUCK. La Belle Sauvage, London, August, 1906. 14 CONTENTS. CHAPTER PAGE L Introduction : Cast-iron Stanchions and Columns . 9 II. Calculations in Designing Stanchions and Columns 16 III. Steel Stanchions, Built and Solid .... 30 IY. Foundations for Columns ; Loads on Columns . 42 V. Calculating Weights of Stanchions, Girders, etc. . 45 VI. Bolts, Connections, and Rivets .... 49 VII. Joists and Girders 59 VIII. Ascertaining Safe Loads on Joists and Girders . 66 IX. Practice of Iron and Steel Construction ... 79 X. Principles of Fireproof Construction . . .98 XL Fireproof Columns and Stanchions . . . . . 105 XII. Fireproof Floors .113 XIII. Fireproof Partitions 135 XIV. Fireproof Stairs, Hoofs, and Ceilings . . . 143 XV.- Fireproof Curtains, Doors, and W ndows . . 150 Index . 157 LIST OF ILLUSTRATIONS. FIG. PAGH .1-4. Sections of Stanchions . 10 5. Section of Cross-shaped Stanchion . . . .11 6. Section of a Square Eibbed Stanchion . . . .11 7. Section of Column with Al- ternative Arrangement of Base Brackets ... 11 8. -Plan of Moulding Flask . 12 9. Section of Moulding Flask 12 10. Wood Pattern for Moulding 13 11. Crystallisation in Square and Circular Castings . 14 12. Curves Comparing For- mulae for Breaking Weight of Columns . . 16 13. Column rounded both Ends 20 14. Column having fixed and rounded Ends . . . 20 15. Column fixed both Ends . 20 16, 17.- Side and Edge Views of Massive Cast-iron Stan- chion 22 18. Plan of Tipper Cap, Figs. 16 and 17 . . . . 23 19. Plan of Tipper Base, Figs. 16 and 17 . . . . 23 20. Steel Joist on Stanchion . 23 21. Plan of Lower Base, Figs. 16 and 17 . . . .23 22, 23. Base of Cast-iron Column 24 24. Breaking on Round Cast- iron Columns ... 26 25. Breaking Weight of Cast- iron Columns . . 26 26. Safe Load on Round Cast- iron Columns . .27 27. Safe Load on Square Cast- iron Columns . . . .27 28. Breaking Weight of Wrought-iron Columns . 28 29-38. Various Sections of Rolled Steel Stanchions . 30 39, 40. Plan and Elevation of Base of a Built Steel Stanchion . . . .31 41, 42. Base of a Built Steel Stanchion . . . .32 43. Plan of Cap of a Built Steel Stanchion . . . .32 44. Breaking Weight of Steel Columns and Stanchions . 33 45. Foundation for Solid Steel Column . . . .34 46. Solid Steel Column, Front Elevation at First Floor Level 34 47. Solid Steel Column, Side Elevation at First Floor Level . 35 FIG. PAGB 48. Solid Steel Column., Base of Column below Ground Floor 35 49. Solid Steel Column, Front Elevation, Third Floor Level 36 50 Solid Steel Column, Front Elevation, Second Floor Level 36 52. -Solid Steel Column, Side Elevation, Third Floor Level 37 52. Solid Steel Column, Side Elevation, Second Floor Level 37 53. Solid Steel Column, Sec- tional Plan at Second Floor Level . . . .38 54. Solid Steel Column, Plan of Base below Ground Floor 38 55, 56. Foundation to Stanchion 43 57, 58. Cast-iron Stanchion . 46 59. Cap for Cast-iron Stanchion 46 60, 61. Compound Girder . . 47 62. Connecting Girders to Built-up Steel Stanchions 50 63. Elevation of Fig. 62 . .50 64. Stiffener to Stanchion . . 50 65 Elevation of Fig. 64 . .50 66. Square Stilting to Cast-iron Stanchion .... 51 67. Elevation of Fig. 66 . .51 68. Spigot Joint to Stanchion . 51 69. Plan of Square Stilting with Lugs . . . .52 70. Elevation of Fig. 69 . .52 71. Plan of Pocket or Bracket Supports to Girders on Cast-iron Stanchion . . 53 72 Elevation of Fig. 71 . .53 73. Stilting with Loose Jaws . 55 74. Elevation of Fig. 73 . .55 75-78. Rivets 56 79, 80. Plus and Minus Threaded Bolts ... 58 81, 82. Compound Girders . . 59 83, 84. Coupled Girders . . 59 85. ast-iron Distance Piece . 59 86. Rolled Steel Joist with Top and Bottom Plates . . 59 87. Joggle and Cleated Joint . 61 88. Common Joggle Joint . . 61 89-93. Notched, Cleated, and Joggled Joints . . 62 94, 95. Distributed and Con- centrated Load . . .66 96, 97. Loaded Cantilever . . 67 98. Girder and Joists Encased in Concrete .... 68 99. Drawing a Parabola . . 69 8 IRON, STEEL, AND FIREPROOF Q&NSTRUGTION. FIG. PAGB 100. Bending Moments from Different Loads ... 70 101. Floor Plan with Joists and Girders . . . . 71 ! 102. Fixing of Girder in Wall . 71 ! 103. Wall influenced by Fixing the End of Girder . . 72 , 104-106. Moment of Inertia of Joist, Girder and Stan- chion 75 107. Support for Floor Joist . 76 103. Cranked Joist for Stairs . 79 109-111. Details of Joints, Fig. 108 80 ' 112. Landing for Stairs . .81 113, 114. Details of Joints, Fig. 112 . . . . . *. 81 115. Framing for Bulkhead . 82 116. Section of Line A B, Fig. 115 82 117. Plan of Trimming for Sky- light . . . . . 83 118. Section of Line A B, Fig. 117 . . . ... 83 119. Floor :n Turret Plan . 84 120. Detail of Cranked Joist A, Fig. 119 84 121. Section on Line A B, Fig. 120 84 122. Support for Trimming, Fig. 119 . . . . 84 123. Knee Girder .... 86 ] 24. Concrete and Slate" Cover- ing for Roof, Fig. 123 . 86 125. Wood Boarded and Slate Covering for Roof, Fig. 123 .. . ... 86 126. Bottom Joint of Knee Gir- der, Fig. 123, Detail Elevation . . . .87 127. Section on Line A B, Fig. 126 .87 128. Top Joint of Knee Girder- Detail Elevation . . 87 129. Section on Line A B, Fig. 128 87 130, 131. Elliptical Skeleton Dome Plan and Section 88 132-135. Details of Joints . . 88 136. Tension in a Hoop . . 90 137. Timber Stanchion with Cast-iron Caps, etc. . . 106 138, 139. Cast-iron Stanchions . 106 140-143. Hollow Built Columns . 108 144, 145. Pease's Tubular Con- struction . . . .109 146, 147. Column and Stanchion Protected with Plaster . 110 148, 149. Column and Stanchion Encased with Solid Con- crete 110 150, 151. Hollow Tile Protection to Column and Stanchion 110 152. Tile Covering for Column . Ill 153. Fireproof Tiling and Terra-cotta . . . .111 154. 155.- Asbestos Slabs . . 114 FIG. PAGB 156. Solid Wood Floor . . 115 157. Hinton and Day's Wood Block Floor . . 116 158, 159. American Wooden Floors .... 117 160. Brick Arch Floor . . .118 161. Blocks to Protect Girders from Fire . . . .118 162. Floor made of Hollow Blocks 119 163. Hollow-keyed Block Floor 119 164. Granolithic Floor 120 165. Granolithic Slab with Strengthening Rib . . 120 166. Concrete Floor Boarded . 121 167, 168. Concrete Arches . 121, 12H 169. Concrete Flat Floor . . 122 170. Concrete Floor with Iron ' Bars Embedded . . .123 171. Concrete Floor with Ex- panded Metal Embedded 124 172, 173. Lindsay's Floors . . 125 174, 175. Fawcett's Floor . . 125 176. Homan and Rodger's Floor 126 177." Mulciber " Floor . . 127 178. Pease's Tubular Floor . 127 179. Stirrup Support . . .130 180. Hollow Tile Protection to Coupled Girder . . .130 181. Floor in Osborne House . 131 182. Section of Side and End Construction Hollow Terra-cotta Flat Arches . 132 183. Section of Hollow Tile Seg- mental Arch . . . 133 184. Lindsay's Cellular Bricks . 136 185. Johnson's Wire Lathing . 138 186. Jhilmil Lathing . . .138 187, 188. Expanded Metal Lath- ing Partition . . .140 189. Sectional Plan of Partition and Door Jamb . . .141 190. Details of Tension Rods and Fixings . . . .141 191. Enlarged View of Ex- panded Metal Lathing . 141 192-194. Varieties of Pease's Tubular Construction . 142 195. Fireproof Cottage with Brickwork Roof . . .145 196. Flat Roof with Asphalt Covering .... 146 197, 198. Ceilings of Expanded Metal 146 199. Clip for Fixing Ceiling Bars under Steel Joists . 148 200. Fixing Ceiling Bars . . 148 201, 202. Domed Ceilings . . 148 203, 204. Sheet-iron Doors . . 151 205, 206. Corrugated Iron Doors 152 207. Sliding Door on Inclined Guides 153 208. Covering Crevices at Bot- tom of Door .... 153 209-211. Cast - iron Window Sashes . 154 IRON, STEEL, AND EIRE- PROOF CONSTRUCTION. CHAPTER I. INTRODUCTION : CAST-IRON STANCHIONS AND COLUMNS. IT is the purpose of this book to treat the subject of iron and steel construction and fireproof construction from the practical side rather than from a strictly theoretical standpoint; for, although a knowledge of theory is essen- tial to the draughtsman before constructional work of any kind can be designed with confidence, still the theory is dealt with fully and clearly by many authors, and there is no excuse for anyone being deficient in that respect. In studying the subject it is advisable always to work out examples, and to draw any diagrams to scale. The centres of all rivets, bolts, and main members are shown in red finished drawings; and the usual colours for the different metals are : Steel, purple lake ; wrought- iron, prussian blue; cast-iron, indigo. The necessity for protecting iron and steel construc- tions from fire hardly needs comment; but, even at the present day, it is not uncommon to see expensive patent fire-resisting floors in a building, while the main girders, columns, or stanchions, wholly or partly supporting them, are not protected at all, or, at the best, inade- quately. Cast iron will remain sound, when supporting a load, to a higher temperature than either wrought-iron or steel. Cast-iron, under a working stress, begins to fail at about 1,300 F., and wrought-iron and steel at about 1,000; and as the heat of an ordinary fire may be any- thing up to 2,500 F., the necessity for adequate protection is apparent; but long before failure occurred owing to the 10 IRON, STEEL, AND FIREPROOF CONSTRUCTION. metal approaching the melting point, collapse or partial destruction would be caused by the expansion of the different members. The expansion of wrought-iron and steel being about iruriwo P ai> t f r each degree its temperature is raised, and that of cast-iron slightly less, it follows that by raising the temperature of a main girder, 25 ft. long, 500 F. only, it would expand 1 in. Cast-iron is largely used at the present time for stanchions, owing to its having great compressive resist- ance, and owing to the facility with which it can be cast to suit all the requirements of structural ironwork _B B - V 1 A ' -f Y///M?/// 1 A 5 -B B / Fig. 1. Section of H Stanchion. Fig. 2. Section of H H Stanchion. Fig. 3. Section of Channel Stanchion. ft Fig. 4. Section of Box Stanchion. in buildings. But steel, being more reliable, is being increasingly used for the same purposes. The Americans are able to convert, with uniform results, tolerably large castings, such as automatic couplings for railway trucks and carriages, after leaving the mould, into what is practically wrought metal. As yet this is a somewhat tedious process, taking about a fortnight, but it is possi- ble that there may be marked development in this direc- tion. The chief points to be considered are the composition of the metal itself, and of the ore used for extracting the carbon. The temperature of the annealing furnace also requires careful regulating. Figs. 1 to 7 show sections of different cast-iron stan- chions and columns, each having its advantages under INTRODUCTION: CAST-IRON STANCHIONS, ETC. 11 special circumstances, but the exigencies of the building will probably settle the point as to whether columns or stanchions are to be employed. In these illustrations A indicates stiffeners, B brackets, and c least width. Their relative strengths for equal weights (ends rounded) are approximately as follows : Hollow column, 100; H- shape, 75 ; cnannel shape, 50. The stanchion is much better adapted for building in brickwork, and is usually adopted when used in that position. A stanchion of H section may be considered as strong as a column of the same Fig. 5. Section of Cross-shaped Stanchion. Fig-. 6. Section of a Square- ribbed Stanchion. Fig. 7. Section of Column with Alternative Arrangement of Base Brackets. sectional area and ratio of length to least width if it has stiffeners about every 3 ft. of vertical height. Stanchions are preferred to columns, because any de- fect in the casting can be more readily detected in the former than in the latter. A frequent defect in columns is that the metal forming the shaft is of unequal thick- ness, owing to the core springing when the metal is poured in ; consequently, cores should be made large, in order to possess sufficient stiffness to resist bending. For building work castings are made by pouring molten iron into sand in which an impression of the article 12 IRON, STEEL, AND FIREPROOF CONSTRUCTION. required has been formed by means of a wooden pattern. The sand D is filled into iron frames, without tops or bottoms, called flasks (shown by Figs. 8 and 9). The wood pattern (Fig. 10) having been dusted with parting sand, so that the sand forming the mould does not adhere to it, an impression of exactly half of it is taken in the sand of the lower flask, the superfluous sand being then removed and the surface smoothed and dusted. The top flask is then placed in position and secured by means of bolts, Fig. 8. Plan of Moulding Flask. Fig. 9. Sectio.i of Moulding Flask. and then filled with sand rammed tightly round the pat- tern. The top flask is then raised, the pattern removed, and the halves again carefully put together without dis- arranging the sand, in which a perfect impression of the pattern remains. The core E consists of a perforated metal tube, bound round with straw bands, the whole covered with sand, and turned and smoothed to represent the hollow of the column. The projections F on the ends of the pattern (Fig. 10) are core prints. They make the impressions in the sand of the flasks to receive the pre- pared core, so that it is perfectly true and central. The damp sand forming the mould is painted with blacking INTRODUCTION: CAST-IRON STANCHIONS, ETC. 13 made from charred oak to prevent the metal from being chilled when poured in. It also, under the action of the molten metal, evolves gases, and prevents too close a con- tact with the sand. One or more passages G are left for the metal to be poured in, and also for the escape of air and gases G' (Fig. 9). The passages for pouring in the molten metal must be arranged so that the metal runs to- gether from different parts at the same time; because if one portion gets partly cool before the adjacent metal reaches it, the iron will not form one mass, but will form what is called a " cold shut." There is no satisfactory way of ascertaining whether a column is of even thickness except by drilling holes through the shaft, and this process must weaken the column, even if the holes are carefully plugged up again. The test by transverse stress, and comparing the deflec- Fig. 10. Wood Pattern for Moulding- Cast-iron Column. tion from several positions, is too expensive for ordinary work. It is very desirable, and is now generally specified, that columns should be cast in a vertical, or, at least, an inclined position, otherwise air bubbles and gases are liable to collect in the upper part of the mould and cause the top of the casting to be honeycombed and consequently weak. When examining castings to ascertain their quality and soundness, several points must be attended to. If, when the edges are struck with a light hammer, a slight im- pression is made, the iron is probably of a suitable quality. If, on the other hand, fragments fly off, the iron is brittle. By tapping the surface all over with a hammer, the pres- ence of bubbles and flaws hidden by vitrified sand from the mould, or purposely stopped with loam, can be easily detected; the ring will be dull, and not clear as will arise from sound metal. The exterior surface should be smooth and clear, and the edges sharp and perfect; an 14 IRON, STEEL, AND FIREPROOF CONSTRUCTION. uneven or wavy surface indicates unequal shrinkage when cooling, and shows bad quality metal. A fractured sur- face should present a fine-grained texture, be of a bluish- grey colour, and possess a high metallic lustre. If by accident a projection happens to be broken off, it should not be " burnt on." If the damage is not sufficient to warrant the rejection of the casting, the part may be bolted on if this can be conveniently done. The process of burning on consists of making a mould of the part broken off to fit in position on the casting. The part of the casting where damaged is then raised to a high tem- perature, and the metal to make good the defect is run in and left to cool slowly. The bases must be made large enough to distribute the load safely on to the stone base; the caps should, Fipf. 11. Crystallization in Square and Circular Castings. on the contrary, be made as small as possible. A pro- jection of more than 6 in. is seldom necessary; otherwise, an appreciable bending stress will be put on the column. The brackets supporting these projections should have a rake of at least 45. Where columns rise tier upon tier, the caps and bases should be turned in a lathe in such a way that the surfaces are not only true but in parallel planes square to the axis of the column, in order that they may be exactly vertical when fixed. The holes for bolts connecting these surfaces should be drilled, and turned bolts used, so that there is no play in the hole; but this is seldom done in practice, the holes being formed to re- ceive ordinary bolts which fit loosely into them. A most important consideration with castings is that there should be no great or sudden change in the thick- INTRODUCTION: CAST-IRON STANCHIONS, ETC. 15 ness of the metal ; all re-entering angles should be rounded off; and, if necessary, metal must be wasted in order to obtain these ends, otherwise the unequal cooling and contraction will cause cracks at the angles. The explana- tion of this is that the crystals forming the iron arrange themselves at right* angles to the surfaces forming the angle (see Fig. 11), so that between the two sets of crystals there is a diagonal line of weakness. Cast-iron contracts -* in. per foot in cooling, so that a pattern for a column 10 ft. long has to be made 10 ft. 1 in. The patternmakers' rules are made proportionately large, so that they can make the pattern direct from the drawing without the trouble of calculating the necessary allowance to be made on each measurement. Where sur- faces have to be machined the parts should be clearly indicated both by colour and in writing on the drawing, so that the patternmaker can see at a glance what is re- quired, and allow the additional thickness necessary. Where appearance is a consideration, and hollow columns with their outer casings would look too large, solid cast-iron or steel columns may be substituted. The comparative liability to oxidation of iron and steel in moist air is : Cast-iron, 100 ; wrought-iron, 129 ; steel, 133. Mild steel rusts faster than wrought-iron at first, and then slower. Cast-iron oxidizes in damp situations, but the rust does not scale off, as in the case of wrought- iron and steel, but eats into the metal to a depth of about y 1 ^ in. and then stops for good. When a casting comes out of a mould, it has a protective coating of vitrified sand, but before it has time to rust one coat of paint should be applied, to be followed by another coat or two when the work is erected. The machined parts should be smeared with a mixture of white-lea'd and tallow. OF THE UNIVERSITY 16 CHAPTER II. CALCULATIONS IN DESIGNING STANCHIONS AND COLUMNS. THE first point to consider in designing a stanchion is the proportion its least width should bear to its height (see accompanying table). For cast-iron it is advisable i S 2 Q. 2 i O 10 F IDLER GORDON 7-0 80 20 30 40 50 60 RATIO OF LENGTH TQ J0IAM.ETER Fig-. 12. Curves comparing- Formulae for Breaking- Weight of Columns. not to exceed twenty times, and for wrought-iron and steel thirty times the least dimension. It must be re- membered that in long columns that is, columns which will fail by bending and not by direct crushing metal near the neutral axis in whatever direction the column will tend to bend is worth little. The strength of a long column depends on the modulus of elasticity of the metal composing it, and on the square of the radius of gyration, which is equal to the moment of inertia about the axis in question divided by the area of the cross section (see table of areas of hollow columns on p. 18). CALCULATIONS IN DESIGN!* J STANCHIONS, ETC. 17 18 IRON, STEEL, AND FIREPROOF CONSTRUCTION. TABLE OF AKEAS OF HOLLOW COLUMNS. Size of Column. Area. Size of Column. Area. Size of Column. Area. 6 x Of 124 10 x If 45-4 13 x 2 69 1 6 x Of- 14 1 11 x 1 31-4 14 x 1 40-8 6 x 1 15-7 11 x 1-|- 34-9 14 x 1-1 50-1 7 x Of 14-7 11 x H 38-3 14 x H 58-9 7 x Of 16-8 11 x H 44-8 14 x 1-| 6:r2 7 x 1 18-9 11 X if 47-9 14 x If 67-4 7 x 14 20-8 11 x If 50-9 14 x 2 75-4 8 x Of 17-1 12 x OJ 306 14 x 2i 79-2 8 x 0| 19-6 12 x 1 34-6 15 x 1 44 8 x 1 22-0 12 x 11- 38-4 15 x 1J 54-0 8 x H 24-3 12 x H 42-2 15 x H 64-6 9 x Of Ik* 12 x If 45-9 15 x 1$ 68-3 9 x 22-3 12 x H 495 15 x If 729 9 x 1 25-1 12 x 1| 53-0 15 x 2 81-7 9 x H 27-8 12 x If 56-4 15 x 2-J- 85-9 9 x 1| 30-4 12 x 1| 59-6 15 x 2 j 90-1 9 x H 35-3 12 x 2 62-8 16 x 1J 57'8 10 x 0| 25-1 13 x 1 37-7 16 x 1$ 68-3 10 x 1 28-3 13 x H 41-9 16 x If 73-3 10 x 1-5. 31-4 13 x li 46-1 16 x If 78-3 10 x 1} 344 13 x li 54-2 16 x H 83-2 10 x 1|- 40-1 13 x ll- 58-0 16 x 2 87' ( J 10 x If 42-7 lS x If 61-9 16 x 2^ 92 6 16 x 1\ 97-2 A built-up stanchion should be composed of ordinary stock sections, otherwise inconvenience may arise through delay in delivery; and the sections should be chosen so as to give the least amount of labour in riveting together. If girders are to run into it, it should be of a shape to simplify the connections. It should also admit of being easily and solidly encased in fire-Kesisting material. The formulae for struts compiled by leading mathe- maticians show considerable variation. Fig. 12 is a dia- gram comparing Gordon's and Fidler's formulae. It will be noticed that Fidler's formula gives higher results for short, and lower results for long, columns than Gordon's. Gordon's is the one chiefly relied upon in practice, and for 36 cast-iron it is B W = i 3 - (see Fig. 25, p. 26). 400 GALGULA TIONS IN DESIGNING STANCHIONS, ETC. 19 B W = breaking weight in tons per sq. in. 36 = the ultimate crushing resistance of the iron per sq. in. in tons. r = ration of length to least width. This formula can be used for hollow or solid columns, and H stanchions if provided with stiffeners. The ends of the stanchions are considered to be fixed, as they can generally be supposed to be in cases connected with building work. If the ends can only be considered to be imperfectly fixed, the formula must be altered to 1 + 100 For solid or hollow rectangular columns, ends fixed. 36 Sf B W = - #', ends imperfectly fixed B W = 1 + 500 1 + 125 BREAKING STRENGTH OF HOLLOW OR SOLID CAST-IRON COLUMNS PER SQUARE INCH. 5 33-9 21-8 1 10 28-8 S 13 3 15 * 23 -, 11 ^ 20 <, 18 ~ 7-2 . i 25 - . 14 ! 5 g 30 5 11 3-6 ^ 35 5 8-9 -1 2-7 o 40 7-2 2-1 i 45 5-9 p| 1-7 * 60 5-0 M BREAKING STRENGTH OF HOLLOW OR SOLID RECTANGULAR CAST-IRON COLUMNS PER SQUAUE INCH. 5 34-3 30 1 10 30 1 20 t 15 24-8 , 129 ^ 20 1 20 ~ 8-6 ' f 25 S 30 S 16 12-9 |. 6-0 4-4 % 35 5 10-4 1 3-3 .2 40 f 8-6 -2 2-6 45 7-1 | 2-1 50 6-0 1-7 20 IRON, STEEL, AND FIREPROOF CONSTRUCTION. For example, let there be a hollow cast-iron column required 15 ft. long to carry a working load of 100 tons. Let its outside diameter be 10 in., then the ratio of its 15 x 19 length to diameter (least width) will be ^ - = 18, 10 and r 2 = 324; therefore, B W = 36 1 + 324 400 = 20 tons. Supposing the column to carry the floor of a dwelling or office where there would be no violent vibrations such as result from machinery, a factor of safety of 6 will be Fig. 14. Column having 1 One End Fixed and the Other Rounded. Fig. 15. Column Fixed Both Ends. Fig. 13. Column Rounded Both Ends. 20 sufficient, so -^ = 3*3 tons per sq. in. will be the safe load, and the number of sq. in. of metal required will be ~^o~ = 31. Now we know the area of the ring of metal and also its external diameter; if there is no table of areas of circles handy, the internal diameter can be obtained as follows : 31 = 7854 (10 2 - d 2 ) d = 7| in., so that the shaft would be lg in. thick; the cap, base, and brackets would be made l\ in. thick. If it is rested on a base stone which would safely resist 20 tons per sq. ft., its area would be -< 5 sq. ft., or 2 ft. 4 in. square. 100 CALCULATIONS IN DESIGNING STANCHIONS, ETC. 21 Gordon's formula, which is one of the best known, is : R = total safe load. A = area of cross section. r = safe resistance of metal per sq. in. I length in in. d least width in in. a = a constant having the following values : Cast-iron both ends fixed Circular (solid) J^Q " ( hollow ) 800 3 Rectangular JgQQ 3 Cross- shaped ^QQ Wrought iron both ends fixed Rectangular, circular, or solid columns Q Angle, tee, cross, square, H and LJ sections In the formula as given on p. 18 it will be noticed that a is taken at 77^ for both hollow and solid columns. If 400 both ends are rounded, make a four times the value given above; and if fixed one end and rounded the other, two and a half times. Roughly, the relative strengths of columns according to the method of fixing are represented by the following figures : Rounded both ends, 1 (Fig. 13) ; one end fixed, the other rounded, 2 (Fig. 14); both fixed, 3 (Fig. 15). The relative strengths of different metals in long columns are cast-iron, 1 ; wrought-iron, 1| ; cast steel ; 2'5. 22 IRON, STEEL, AND FIREPROOF CONSTRUCTION. Fig. 16. Side View of Massive Fig, 17. Edge View of Massive Cast-iron Stanchion. Cast-iron Stanchion. CALCULATIONS IN DESIGNING STANCHIONS, ETC. 23 Assume a cast-iron column 20 ft. long, 6 in. diameter, in. thick, and find the safe load with factor of safety 6. 8 ' 6 * 6 17.2 tons. 1 + 1600 "800" * i '$ I ^H ; ; ; f i _ i i_ 1 o ; | ; H 1 ! 1 1 I ' J. Fig. 18. Plan of Upper Cap, Figs.- 16 & 17. Fig. 19. Plan of tipper Base, Fkrs. 16 & 17. Jl pier. 20. Rolled Steel Joist Resting on Lower Stanchion, Figs. 16 & 17. Fig. 21. Plan of Lower Base, Figs. 16 & 17. Figs. 16 to 21 give full details of a massive cast-iron stanchion. The letter references in Figs. 16 to 21 are thus explained : A, stiff eners, about 3-f t. 4-in. centres ; B, 3-in. by 3-in. angle stringer to receive floor joists; C, i-in. plate; D, 2-in. metal; E, 2^-in. metal; F, 2^-in. metal; G, rivets countersunk; H, |-in. diameter holes; J, 1-in. diameter holes. Figs. 22 and 23 show a plan and elevation of the base of a cast-iron column K, 15 ft. high, 14 in. diameter, If in. thick, which was designed to carry safely about 240 tons. 24 IRON, STEEL, AND FIREPROOF CONSTRUCTION. When it had no more than half this load on it, the brick pier in cement L, 5 ft. square, cracked vertically and T 5 i Fig. 22. Plan of Base of Cast-iron Column. I. I * M T I . I Fig. 23. Elevation of Base of Cast-iron Column. bulged badly, and was shored up just in time to prevent a collapse. The grey granite base stone M, 1 ft. thick, CALCULATIONS IN DESIGNING STANCHIONS, ETC. 25 cracked into four pieces, as shown on plan at N. The column base O, If in. thick, with If-in. brackets P resting on a f-in. iron-cement bed, remained perfectly sound. Fletton bricks with a frog, in cement, were used in the pier. It should have been built in blue wire cut bricks, which would not have a frog. Fletton bricks are made by the dry-clay process, the clay being ground and sub- jected to a pressure of about 200 tons on the brick in moulding. They were very close in texture, and had good surfaces and arrises, but appeared to lack toughness. Probably, however, they would safely withstand a load of 5 tons per foot super, if built in cement and properly bonded. Directly under the base stone was a 2-in. cut course of bricks R; consequently, the stone had an un- even bed, and this probably hastened the failure of the entire brick pier. Now that iron and steel enter so largely into the con- struction of buildings, an Act should be passed governing this construction very fully ; for the importance of any member corresponds with the work it has to do, and a failure is a far more serious matter now than it was in the old-time brick and timber erections. The New York, Boston, and Chicago building laws require cast-iron columns and stanchions to be computed by the formulae graphically represented in the diagrams (Figs. 24 to 26). It will be noted that New York is satisfied with a factor of safety of 5 that is, 16,000 Ib. per sq. in. for an ultimate strength of 80,000 Ib. per sq. in. ; whereas Boston and Chicago require a factor of safety of 8 10,000 Ib. per sq. in. The contrast shown by the dia- grams is remarkable, for a column which would be allowed to carry 160 tons in New York would only be allowed 125 tons in Boston, and 115 tons in Chicago. The New York building law stipulates a minimum thickness for cast-iron of f in., and the height must not exceed twenty times the least dimension. Wrought-iron or steel columns or stanchions must be at least ^ in. thick, and not exceed thirty times the least dimension in height. The usual practice in England is to make the thickness of metal in the shaft of a hollow cast-iron column one- tenth of the diameter; in no case should it be less than one-twelfth. 26 IRON, STEEL, AND FIREPROOF CONSTRUCTION. CBS PER SO. IN 80000 taboo .50000 15 ;20 RATIO OF LENGTH TO DIAMETER Fig. 24. Curves showing- Breaking Weight of Round Cast-iron Columns. TONS PER SQ. IN 10 5 20 25 RATIO OF LENGTH TO LEAST SOLID OR HOLLOW RECTANGULAR COLUMNS -JENDS FIXEtJ \ SOLID OR HOLLOW COLUMNS -ENDS FIXED SOLID', OR HOLLOW COLUMNS-ENDS POUNDED SOLID OR HOLLOW COLUMNS -ENDS-ROUNDED Fig. 25. Curves showing Breaking Weight of Cast-iron Columns. CALCULATIONS IN DESIGNING STANCHIONS, ETC. 27 Fig. 26. Curves showing Safe Load on Round Cast-iron Columns. ffO 15 20 25 BATK3 OF LENGTH. TO SIDE Fig. 27. Curves showing Safe Load on Square Cast-iron Columns. 28 IRON, STEEL, AND FIREPROOF CONSTRUCTION. The metal on the surface of a casting is better and stronger than that in the body. Very thick castings from the same smelting are found not to possess the same ultimate strength per unit of area as comparatively thin ones. SOLID RECTANGULAR ENDS FIXED OR CHANNEL. FIXED ID RECTANGULAR ENDS FREE ANGLE OR- CHANNEL ENDS FREE 30 36 40 NATIO OF LENGTH. TO LEAST WIO1M Fig. 28. Curves showing Breaking Weight of Wrought-iron Columns. Gordon's formula for solid rectangular pillars of 16 wrought-iron is, ends fixed, B W = ; ends imper- 1 3000 fectly fixed, B W = - -. For angle, tee, channel, and cruciform iron, ends fixed, B W = - -; ends imperfectly fixed, B W = ^--^; l + 250 900 These formulae are shown graphically in the diagram given above (Fig. 28). CALCULATIONS IN DESIGNING STANCHIONS, ETC. 29 BREAKING WEIGHT PER SQUARE INCH OF SOLID RECTANGULAR COLUMNS OF WROUGHT IRON SOLID ROUND COLUMNS 15 PER CENT. LESS. Ratio of length to least width. Ends fxfd. Ends rounded. 5 15-8 155 10 15-5 14 1 15 lo-O 12-3 20 14 1 10-4 2o 13-2 8-7 80 12 3 7-3 35 11-3 6-1 40 10-4 5-1 45 9-5 43 50 87 3-7 30 CHAPTER III. STEEL STANCHIONS, BUILT AND SOLID. ROLLED steel joists of suitable sections are also much used as stanchions, either singly or compounded with others, or with channel steels, Z bars and plates, as shown in Figs. 29 to 38. The caps and bases are formed with Fig. 29. Fig. 32. Fig. 30. Fig. 31. ' Fig. 33. Fig. 34. Fig. 29 Rolled Steel Joists used as Stanchion. Fig. 30. Rolled Steel Joist with Flange Plates. Fig. 31. Four Rolled Steel Joists Combined. Fig. 32. Three Rolled Steel Joists and Plates Combined. Fig. 33. Three Rolled Steel Joists Combined. Fig. 34. Two Channels Combined with Rolled Steel Joist. plates secured to the shaft by angle and tee steels as shown in Figs. 39 to 43. In the cap and base the pitch of the rivet has to be varied to suit the connections, but in the J- itf f Fig. 35. Fig. 36. Fig. 37. Fig. 38. Fig. 35. Two Channels Combined with Plates. Fig. 36. Four Channels Combined. Fig. 37. Four Z Bars Combined with Plates. Fig. 38. Column in Four Sections Riveted Together. shaft 4-in. to 6-in. pitch is usual. In these illustrations A indicates f-in. plate, with rivets countersunk on the under side, and B i-in. plate. For built steel stanchions of British manufacture, such as those illustrated in Figs. 29 to 38, the following formula may be used : STEEL STANCHIONS, BUILT AND SOLID. 31 Fig. 39. Plan of Base of a Built Steel Stanchion. Fig. 40. Elevation of Base of a Built Steel Stanchion. Breaking weight per sq. in. with both ends fixed = 30 30 -- 3-; with ends free = - %. If foreign steel = 900 225 24 .,-; ends free = * ' 24 r 900 1 + , 225 For dead loads a factor of safety of 4 is sufficient, and for live loads 6. 32 IRON, STEEL, AND FIREPROOF CONSTRUCTION. Fig. 41. Plan of Base of a Built Steel Stanchion. Fijr. 43. Plan of Cap of a Built Steel Stanchion, Fig. 42. Pig. 42.~-Elevation of a Built Steel Stanchion. STEEL STANCHIONS, BUILT AND SOLID. 33 Solid rectangular mild steel columns, ends fixed, 30 30 B W = - _!?J 2480 ends free = ' + 620 Solid round mild steel columns, ends fixed, B VV 30 30 5; ends tree = - . 1 1 + llOO r 350 The above formulae are shown graphically in the dia- gram given below (Fig. 44). r ONS PER SQ IN 30 SOLID RECTANGULAF ENDS FIXED SOLID COLUMNS ENDS FIXED STAMOHJONSi ENDS FIXED 'SOLID RECTANGULAR ENDS FREE ID COLUMNS ENDS FREE TANCHIONS ENDS FREE RATIO OF LENGTH TO LEAST WIDTH Fig. 44. Curves showing Breaking Weight of Steel Columns and Stanchions. Figs. 45 to 52 show sectional front and side elevations of solid steel columns supporting three floors, and sup- ply details of the construction of the foundations and girder connections ; Fig. 53 being a sectional plan at second floor level, and Fig. 54 a plan at base be- low ground floor. These figures are from working drawings kindly supplied by Messrs. Richard Moreland 34 IRON, STEEL, AND FIREPROOF CONSTRUCTION. Fig. 46. Front Elevation at First Floor Level. 45. Base ancl Foundation of Column below Ground Floor, STEEL STANCHIONS, BUILT AND SOLID. 35 and Son, Limited, engineers, 3, Old Street, E.G. It will be noted how neatly the girder connections are made ; and the columns, being small, can be adequately protected without giving them a clumsy appearance. Indeed, such Fig. 47. Side Elevation First Floor Level. Fig. 48. Base of Column below Ground Floor. a section, exposing as it does the least possible surface in proportion to area, would undoubtedly remain sound if unprotected longer under fire than any other section. There is little doubt that there is a great future for these 36 IRON, STEEL, AND FIREPROOF CONSTRUCTION. columns in London, and in other centres of population, where space is so valuable, and especially for shop fronts, where the least obstruction to space or light is resented. Fig 1 . 49. Front Elevation Third Floor Level. Fig. 50. Front Elevation Second Floor Level. The columns are made from ordinary mild rolled steel, arid are very uniform in nature. The caps and bases are turned out of solid steel and shrunk on, this connec- STEEL STANCHIONS, BUILT AND SOLID. 37 tion being equal in strength to a solid flange, care being taken to provide enough shrinking area. To obtain this, the thickness of the cap and base should be about half the 8X4 8X4 RS.J. - Fig. 51. Side Elevation Third Floor Level. Fig:. 52. Side Elevation Second Floor Level. diameter of the column. The bearing surfaces are all turned after shrinkage, and the result is a very neat and first-class engineering job. The firm last named keep $8 IRON, STEEL, AND FIREPROOF CONSTRUCTION. A [Fig. 53. Sectional Plan at Second Floor Level. CONOR rre (> aSouwSE Fig, 54. Plan of Base below Ground Flo3r STEEL STANCHIONS, BUILT AND SOLID. 39 a large stock of these columns, and, having recently put down a special modern plant, can supply them almost as cheap as cast-iron columns and quite as cheap as steel stanchions to carry the same weight. A steel beam grillage (10-in. by 6-in. rolled steel joists) foundation is shown. The beams are embedded in good Portland coment concrete, and consequently distribute the load over a sufficiently large area of ground, without putting tensile strains on the concrete. In ordinary cases 3 tons per sq. ft. can be safely imposed on ground in the London district, but, of course, in bad localities and in proximity to the river this amount must be considerably reduced, and the area and strength of the grillage pro- portionately increased. A table (taken from Messrs. Moreland's catalogue) of strength for solid steel columns is given. It will be seen from this table that a 9-in. solid steel column, 14 ft. long, will carry 210 tons safely. To support the same load under similar conditions a 15-in. diameter hollow cast- iron column, 1^-in. thick, would be required, or a 15-in. by 18-in. built steel stanchion, composed of two 14-in. by 6-in, rolled steel joists, and two 18-in. by ^-in. cover plates. To equal a 6-in. solid steel column, a 10-in. dia- meter hollow cast-iron column, ij in. thick, would be re- quir,ed, or a built steel stanchion composed of one 10-in. by 6-in. rolled steel joist, and two 12-in. by ^-in. plates. The above comparison illustrates very clearly the advan- tages of the solid steel column. Notes, of which the following is the substance, are appended to the table : (1) The steel in the rolled bars is of superior quality, and so uniform in its nature that it entirely supersedes cast-iron, which as a metal for columns is so very unsatisfactory that the firm con- sider that the increased reliability that can be placed on the solid steel columns makes their use very desirable. (2) It may appear at first sight that hollow columns of steel should be used, but at the present time the steel makers are not prepared to supply these at anything like the cost of solid steel ; and if cast steel were used it would cost a sum too high for practical purposes. A solid steel column is theoretically an expensive section to use, but the practical issue is in favour of it as regards expense. 40 IRON, STEEL, AND FIREPROOF CONSTRUCTION. 1^ CO Ci -^ -H C CO ^-H >O 05 I > ON J <>) Tfl r 1 I 1 1 *""'" 1 ' I C* ^ 'b"s y itiMi'j JIM loofauo suo} m pnoi painqwsitj Tf< TO O ri< GO <>I i I TJH t> Tj* (MCTiOOOSCOOOOr-i ^-i^-(CC-^t^O^-iO i I i 'M 1^3 ^ * iO >c O >O CO t~- O O O t^- wcbo3Obcbb^-i i-H = 18 tons, the equally distributed load, which would give the same maximum moment of stress; or 9 ton's concentrated at the centre would have the same effect; the bending moment from a load concentrated at the centre being or double the 4 moment from a uniformly distributed load. For a beam carries double the load equally distributed that it will if concentrated at the centre. If the beam, in addition to the concentrated load, had an equally distributed load of 3 tons, it would be more difficult to find the maximum bending moment. In such a case it is better to draw a diagram and set out care- ASCERTAINING SAFE LOADS ON JOISTS. 71 fully the moments obtained to a convenient scale (see Fig. 100). The maximum moment from the concentrated load is of course directly under the load, and equals 33-3 foot- tons; and as this moment decreases gradually, vanishing at the supports (as can be seen by working out an ex- ample), if E c be drawn to scale to represent this moment, and the point c be joined to A and B, the bending moment at any point in the beam from the 10-ton load can be obtained by scaling the vertical. The maximum bending moment at the centre from the Fig. 101. Floor Plan with Joists and Girders. 102. Fixing of Girder in Wall, Section. equally distributed load of 3 tons = 5'6 foot-tons, and the curve of stress will be a parabola, as explained before; and if the stresses from these two loads be combined, we get the irregular figure A D B, from which we obtain the total stress in the beam at any point arising from both loads. It is at once evident from the figure that the maximum stress is under the concentrated load, and by scaling E D we obtain its value = 38'3 foot-tons. Knowing this, and equating it with the maximum moment for an equally distributed load, we get = 38'3 and w ~ 38-3 x 8 y= = 20'4 tons, the total uniformly distributed load, which would give the same maximum moment of stress. Although, by taking special precaution, it may be 72 IRON, STEEL, AND FIREPROOF CONSTRUCTION. possible to fix the ends of a joist carrying a small load, it is a mistake to imagine that a uniformly loaded girder has only to have its ends firmly pinned in the wall to be considered fixed, and consequently able to carry 50 per cent, more load. Fig. 101 is a plan of a floor supported at 10-ft. centres by 14-in. by 6-in. rolled steel joists. Fig. 102 shows one end of this girder with a 14-in. bearing in an 18-in. wall, and with a stone 6 in. thick at top and bottom to give a better hold of the wall. The clear span is 21 ft., and it is assumed that the floor joists are placed against the walls, so that the load on the side bays also 2lCWT. FLOOR Fig. 108. Elevation through Floors showing Portion of Wall In- fluenced by Fixing the End of Girder. comes on the girder, and not directly on the wall. Let it be also supposed that there is a similar floor above the one under consideration, and also a 1^ cwt. flat roof over (see Fig. 103). Imagining the end of girder fixed, the w ft bending moment at the point of support will be , and if it is a 2-cwt. floor, the total load on the girder is 21 ft, by 10 ft. by 2 cwt. = 420 cwt. = 21 tons, or 1 ton 7^ per foot of span, and - = 36'75 foot-tons. To counter- act this bending moment, there is the weight of the wall itself, the floor above, and the roof acting through the of gravity of the wall, that is, the centre in this ASCERTAINING SAFE LOADS ON JOISTS. 73 case. Weight of wall 18 in. thick, 22 ft. high, and 10 ft. wide, 22 x 10 x l|- cwt. = 293 cwt. ; parapet, 4 x 10 x f cwt. = 27 cwt. ; floor, 10'5 x 10 x 2 cwt. = 210 cwt. ; roof, 10-5 x 10 x li cwt. = 158 cwt. = 688 cwt., or nearly 34^ tons, acting with a leverage of 9 in. or '75 of a foot; 34'5 x -75 = 25'87 foot-tons to resist 36'75 foot-tons, the bending moment on the girder. Consequently the girder cannot be considered fixed, as it would move the wall first, apart from the consideration of the stonework or brickwork crushing. It will be noticed in the above calculation that the wall is taken of the full width to the level of the bearing of the girder in question; in reality the most that can be ex- pected is a V-shaped mass rising from the top of the girder and spreading out, following the bond in the work until it reaches the wall influenced by the adjoining gir- der (see Fig. 103). But no allowance has been made for the adhesion of the mortar, which might be anything from 20 Ib. to 100 Ib. per square inch, according to the quality of the mortar used, so that the extra quantity of wall taken may compensate for this. It may be easily ascer- tained whether it would be possible to fix the end by means of holding-down bolts to something immovable, such as a column cap. Take f-in. bolts, which may be considered to safely resist 2i tons each in tension; the average lever- age these could obtain would be 6 in. Therefore, the number of bolts x required would be x x 2*5 x '5 = 36*75, x = 30, a number it would be quite impossible to insert. From the figures above given it will be apparent how necessary it is to discover under what conditions the safe loads in manufacturers' tables apply. Frequently in these tables the ends are considered to be fixed ; but as this condition seldom obtains in practice, due allowance should be made in each case for instance, if the load given is a uniformly distributed one, by deducting one- third to make it apply to free ends. A factor of safety of three is most common in makers' lists; but, for good work, in no case should a factor of less than four be employed. To avoid trouble from deflection, the most satisfactory method in building work is to specify that of an inch per foot of span ia the maximum de- oction under full working load that will be permitted. 74 IRON, STEEL, AND FIREPROOF CONSTRUCTION. Frequently, in the case of joists of foreign manu- facture, there is no table of strength at hand; but when the depth, breadth, and weight per foot run are known, the a'pproximate safe load (factor of safety three) can be obtained from the following formula : W - -95 (w - '3 bd) Y _LJ where W = safe uniformly distributed load in tons. ID weight of beam in Ib. per foot. b = breadth in inches. d = depth in inches. L = span in feet. The above is for 24-ton to 26-ton steel, the usual strength of foreign manufacture. If it is required to be used for English 30-ton to 32-ton steel, it must be altered to the following : W 1-2 (w - -3 bd) f. J_j Another useful approximate formula for English steel joists or plate girders is : 7 a d . 5'5 a d fe L = , and tor foreign, S L = . fe 5 S L = safe uniformly distributed load in tons. a = area of one flange in inches. d = depth in inches. S = span in feet. The above are only approximate, and must only be used to obtain some idea of the section required when there are no other data available. The accurate mathematical formula for obtaining the moment of resistance of any beam is M = . y M = moment of resistance in inch tons. r = limiting stress per sq. inch of metal. y = half the depth. I = moment of inertia, explained later. By equating this formula with the bending moment, what- ever it may be, the safe load on the beam can be obtained. Each side of the equation must, of course, be in the same terms that is, inch-tons or foot-tons. The moment of inertia of a rectangular beam is T Y b d 3 ASCERTAINING SAFE LOADS ON JOISTS. 75 so that its value varies as the breadth and as the cube of the depth. Fig. 104 shows how the vertical moment of inertia of a joist is obtained. The joist is first considered as a solid rectangular beam, and then the voids between the flanges are deducted. I = T v- (b & - b' d'*). Imagine Fig. 104 to be a 14-in. by 6-in. rolled steel joist with a web thickness of T 7 of an inch, and an average flange thickness of f in., then I = -^ (6 x 14 3 - 5'56 x 12-75 3 ) = 412. Fig. 104. Fig. 105. Fig. 106. Fig 1 . 104. Moment of Inertia of a Single Joist. Fig. 105. Moment of Inertia of a Girder or Stanchion. Fig. 106. Moment of Inertia of a Compound Girder or Stanchion. In Fig. 105 the flanges are divided into a number of rectangles, and I can be obtained as above described, or the same result may be obtained more simply as follows : I = T i_ [b d* + V (d* - d?) + b" (d" z - d't) + b"' (d" f * - d" 3 )}. Working out the previous example by this method also we get I = T V {'44 x 12'7o + 6 (H a - 12-75 3 )} = 412 as before. The moment of inertia for this section is given in the manufacturers' tables as 422; the slight difference arises from the curved part of flange against web not having been included. In the case of a compound girder (Fig. 106), pro- ceeding by the first method mentioned, we get I = j_ {6^3 _ 6 / rf /s _ b"d" A }. In this case the rivet holes should also be deducted for the bottom flange, which is in tension; there is no reason 76 IRON, STEEL, AND FIREPROOF CONSTRUCTION. why they should be for the top flange, which is in com- pression, providing the rivets completely fill the holes. If b'" is the combined width of -the rivet holes, the deduction for both flanges would be I = T i_ (b'" d? _ V" d"*}. Take the case of a compound girder (Fig. 106) com- posed of two 14-in. by 16-in. rolled steel joists having average flange thickness of -f^ in. and web \ in., with 14-in. by ^-in. plates top and bottom, with two |-in. rivets in each flange, then I = _i_ {14 x 15 s - 2 x 143 _ 11 x 12-38}. I = 1774 with no deduction made for rivet holes. The I for rivet holes = T u{ 1-5 x 15 s - 1-5 x 12'3 3 }= 190. 1774 190 = 1584, the moment of inertia of the sec- tion which is given in the manufacturers' table as 1599. Fig. 107. Support for Floor Joist on Girder and Boarded Floor Finish : Section. Now proceed to work out the girders and joists as shown in Fig. 101. It will be noted that the concrete rests in a chase in the wall parallel to the floor joists, so that only half the load of the side bays comes on the girder. The area of the floor supported by the girder is consequently 10 x 18 180 ft. super, at 2 cwt. 18 tons. Looking through the maker's list, 14 in. by 6 in. at 46 Ib. appears to be a likely section. Its depth will be -^ of the span and its width T L ; this latter ratio is rather high, although seldom considered in practice, but as the joists will run into it as shown in Fig, 107 and in Fig, 08, it would be stiffened sideways, ASCERTAINING SAFE LOADS ON JOISTS. 77 By the approximate rules given before for obtaining the safe load uniformly distributed when only the weight per foot, the breadth, and the depth are known : W = 1-2 (w - '3 b d) ^ = 1-2 (46 - -3 x 6 x 14) =: 17-56 tons, lad 3-75 x 7 x 14 and W = - - - - 1 r5 tons. By the accurate method of equating the bending mo- ment - - with the moment of resistance wj _ 2r I w x 252 _ 2 x 10-6 x 422 y ~d 8 14 from which w = 20'3 tons safe load, and this agrees with the manufacturers' tables. Having ascertained that the girder is strong enough, now see whether it is stiff enough ; its deflection should not materially exceed -^ in. per foot of span. The formula for the deflection in inches of a girder 5 w ft having a uniformly distributed load is D = - * oo4 iL 1 w $ and with a load w at the centre D = -r-Q-^p 4:0 _EJ 1 where w load in tons; I = length of span in inches; E = modulus of elasticity 12,000 tons; I = moment of inertia. Working out the first formula we find the deflection is 5 x 18 x 9 52 3 D = 384 x 12000 ^x 422 = ' U f a " inch> which is " ly a trifle more than -^ in. per foot of span. The floor joists must next be considered; each one has to carry 10 ft. by 3 ft. of floor at 2 cwt. 3 tons. By the table given before, it is found that the most suitable joist for the present case is a 5-in. by 3-in., at 11 lb., which gives 2'6 cwt. safe load per ft. super. But proceeding to work out the case first by the ap- proximate formula, which will be found to give better results for the smaller joists, we get 78 IRON, STflEL, AND FIREPROOF CONSTRUCTION. w = 1-2 (11 - -3 x 3 x 5) T % = 3-9 tons 7 x 1-12 x 5 and w = -- ryr = 6-y'l tons, and using the accurate formula I being 13'6 w I _ 2 r I w;xl20_ 2 x 10-6 x 13-6 IT = _ each row on each side of the joint by resistance to shearing. The sectional area of one f-in. rivet is '44 sq. in. ; and as the rivets pass through the two fish-plates and the web of the 10-in. by 5-in., it is evident that the rivets must be sheared at two sections before the joint can fail, so that, doubling the rivet area, '44 x 2 = '88 sq. in., and multiplying this by 5, the safe resistance to shearing per sq. in. of the metal, we get '88 x 5 = 4*40 tons as the resistance of each rivet; and dividing the total resistance required by the resistance of one rivet, we get the number 32 - 4 of rivets required - = 7J ; but as there cannot be half 44 a rivet, in order to have sufficient in the joint, there must be 8 rivets at top and bottom on each side of the joint, and supposing they are placed at 3-in. pitch, each fish- plate would have to be 4 ft. long 2 ft. on each side of the joint. The two sections Figs. 124 and 125 show alternative roof coverings. In Fig. 124 the rafters H obtain inter- mediate support on a wood plate J bolted to the top flange of a small rolled steel joist which is cleated to the web of the main girder. In Fig. 125 small rolled steel joists are placed 2 ft. centre to centre and cleated to the web of main girder, and then the slope is centred and filled in with breeze concrete, the surface of which is smoothed and the slates nailed to it direct. Figs. 130 and 131 show a plan and section of the fram- ing for an elliptical dome of 30 ft. external diameter and 11 ft. rise, with a 7-ft. diameter opening for light in the OF THE i 90 IRON, STEEL, AND FIREPROOF CONSTRUCTION. crown. A 7-in. by 4-in. angle is used for the bottom curb (see Fig. 132), and from it the ribs spring. The bottom curb is in tension, as it prevents the ribs from spreading under the load. There are two intermediate purlins (see Figs. 130 and 133). The first one is placed where the tangent to the curve makes an angle of 52 with the horizontal, as it is at this point that the hori- zontal thrust is at the maximum, consequently this is the point at which the dome would fail. The top curb (see Fig. 134) is in compression, and, owing to its having to provide a fixing for the light framing, an angle steel is used. Channel steels might equally well be employed for both top and bottom curbs. Joints are made in the curbs by means of cover plates, with sufficient rivets or bolts to transmit the stress. Fig. 136. Method of Obtaining the Tension in a Hoop. Every third rib, as shown in the illustration, is made of two 4^-in. by 2-in. channel steels, placed back to back and cleated at each end to the curbs (see Fig. 135). The inter- mediate ribs are of 5-in. by 3-in. rolled-steel joists, and each is cleated at ends to the curbs. The ties or purlins are 4-in. by 3-in. rolled-steel joists, single cleated to the ribs. These, besides acting as a hoop round the dome, give support to the breeze concrete filling. As the top curb gives no support to this filling, a 4^-in. by 2-in. channel is fixed to do so. All the connections are shown riveted together ; but, for convenience, and in order to facilitate erection, it may be advisable to use bolts in many of the joints. The centering for a concrete filling to a dome of this character requires much preparation and a considerable degree of ingenuity in putting together. It must also remain in position until the filling is thoroughly set a matter of some weeks. The dome shown in Figs. 130 and 131 may be considered theoretically without touching trigonometry. The load to be carried is very small, especially if the dome forms PRACTICE OF IRON AND STEEL CONSTRUCTION. 91 part of some internal ornamentation and is in reality only a shell. Take the load as 1 cwt. per ft. super, of horizontal surface. Although the pressure on the curbs is not continuous round the circumference, but concen- trated at points, the curb may be considered in the same way as a pipe under pressure would be. Considering a half-section of a pipe (see Fig. 136) of which d is the diameter, r the radius, and p the pressure per sq. in. of whatever the pipe contains, the force tending to burst it is d x p. To resist this force there is the metal on each side of the pipe, so that the tension T in the metal on one side only must be T = - ; or r p, where r is the radius, 2 p in the case under consideration is obtained from the thrust of the twenty-four ribs, so that the pressure per ft. of circumference, if t is the thrust in each rib 24 t 3-82 t P = x r 3-82 t and as T = r p and p = - r 3-82 t T = r x - = 3-82 t r The thrust on the top curb from each rib may be ob- tained by taking moments. The load supported by the ribs being triangular on plan, its centre of gravity will be at a point one-third in from the outer curb, or, in this case, 5 ft. The load coming on each rib is the area of the triangle multiplied by the weight per ft. super. : 303 X * * l = 29-15 cwt. = 1-47 ton, By moments about the bottom curb, the horizontal thrust at the top H, multiplied by its leverage, 11 ft., must equal the load on the rib acting at its centre of gravity multiplied by its leverage, 5 ft. : H x 11 = 1'47 x 5. H = '67 ton; and by the equation T = 3'82 t. fl and t being similar, T = 3'82 x -67 = 2'56 tons = the compression in the top curb. 92 IRON, STEEL, AND FIREPROOF CONSTRUCTION. The horizontal thrust on the top curb having been obtained, '67 ton, we can obtain the thrust in the rib by drawing a triangle of forces, representing the horizontal thrust, '67 ton, and the load on the rib, 1'47 tons. So that the thrust in the rib, represented by the hypo- thenuse, will be = v/-67 2 + 1'47 2 = 1'62 tons. Owing to the method of fixing, the rib is not likely to bend sideways, but it is free to do so vertically. Its length is 18 ft., and a depth of 5 in. gives a ratio of 43; so that, using the formula given before, the safe load per sq. in. on the strut will be (see p. 31). S. L. = T: rA" 1 ^ ^ '46 tons per sq. in. * T 9^0~ So that 1 sq. in. is more than sufficient ; but it would not be advisable to use a less section than 5 in. by 3 in. at 11 lb., giving a sectional area of 3*25 sq. in. The tension in the bottom curb will be the same as the compression in the top one ; but, though this is so small, it is necessary to employ a comparatively large section of curb in order that the connections may be properly made. In the case of a skeleton dome, with or without concrete filling, in an exposed position, diagonal braces should be inserted in each of the panels formed by the ribs and purlin rings. A more correct method would be to take the weight per ft. super of dome, then find the centre of gravity, and then draw the parallelogram of forces. The following are the usual safe resistances in tons taken for steel, wrought-iron, and cast-iron (factor of safety 4) : Tension. Own- Shearing. Bearing, pression. - Steel ... 6-58 5 8 Wrought-iron ... 5 4 4 5 Cast-iron 1'5 8 2*4 10 It is sometimes necessary to use timber to shore up girders or to support tackle to raise them; and in order to give some idea of the sizes required, the following formulae are supplied : Safe uniformly distributed load in cwt. for a fir beam (factor of safety 5). j ^o b = breadth in inches. S, D, L. = - d = depth in inches. s = span in feet. PRACTICE OF IRON AND STEEL CONSTRUCTION. 93 For pitchpine, multiply the result by l|. For a square fir strut with fixed ends, the breaking weight per sq. in. in tons 2*5 2-5 B. AV. = -- ends rounded = - 3 1 + i*> l + G 2 For pitchpine, o o B. W. = 5 ends rounded = r* _ ?- 1+ 250 1+ ^2 A factor of safety of 6 to 10 must be used. Taking the force required to crush a cube of any wood as unity, ths force to break a timber strut with fixed ends is Length 12 times least thickness % f) 4 i )) ^* 55 55 5) "2" Qft .!_ 55 J5 55 55 8 4-8 ! 5) 5 55 55 6 W 60 yV 55 ' J 55 51 55 "24" The following are the ultimate crushing resistances for use in the above table : Oak, 3^ tons per sq. in ; fir, 2| tons per sq. in.; pitchpine, 3 tons per sq. in; yellow pine, 2 tons per sq. in. The following is a specification to accompany drawings and bill of quantities for first-class engineering work. For ordinary building work, the specification, if one were furnished at all, would not be nearly so strict : " On receipt of the drawings, the contractor is to ex- amine them carefully before ordering the iron and steel, and is to call the attention of the engineer to any dis- crepancies between the drawings as scaled and the figured dimensions, or between various parts of the drawings, and the engineer's decision on these points shall be final. The whole of the iron and steel used must be of British manufacture. The steel to be made by the open-hearth process. The wrought-iron plates shall be free from blis- ters, scales, laminations, and all other defects, and shall be of such quality as to have an ultimate tensile strength of not less than 22 tons per square inch, with an elonga- tion of not less than 8 per cent., measured in a length 94 IRON, STEEL, AND FIREPROOF CONSTRUCTION. of 8 in., when tested in the direction of the fibre of the iron, and also to admit of bending cold without fracture as follows : THICKNESS IN INCHES. To BEND TO AN ANGLE OF | and A ... 35 with the grain, 15 across the grain. ?g and | ... 50 with the grain, 20 across the grain. Y\ and | ... 70 with the grain, 30 across the grain. " The steel plates shall be free from blisters, scales, laminations, and all other defects, and shall be of such quality that strips cut lengthwise shall have an ultimate tensile strength of npt less than 26 tons, and not exceeding 30 tons per square inch of section, with an elongation of at least 20 per cent., measured in a length of 8 in. " Strips of steel cut crosswise or lengthwise, li in. wide, heated uniformly to a low cherry-red, and cooled in water of 82 Fahrenheit, must stand bending double in a press to a curve of which the inner radius is one and a half times the thickness of the steel tested. The ductility of any plate, beam, angle, etc., may be ascertained by the application of one or both of these tests to the shearings, or by bending them cold by the hammer. The angle and T-iron must be of the forms and sections shown on the drawings, and must be capable of standing the same tensile and bending tests as are specified for the plates. " The angle T, H, and C steel to be of the same tensile strength, with the same percentage of elongation as the plates, and to stand such bar tests, both hot and cold, as may be sufficient, in the opinion of the engineer, to prove soundness of material and fitness for the service. The rivet iron must be of the very best and toughtest quality, and shall have an ultimate tensile strength of not less than 24 tons, and shall be capable of being bent through an angle of 120 when cold, without showing signs of frac- ture. The rivet steel must be of such quality that when tested in the direction of its length it shall have an elonga- tion of 23 per cent, in 10 in., and an ultimate tensile strength of not less than 26 tons, and not exceeding 30 tons, per sq. in., and to bend double when cold without cracking or splitting. The plates to be of the exact PRACTICE OF IRON AND STEEL CONSTRUCTION. 95 thicknesses as figured on the drawings, and to be uniform throughout. " The plates shall be carefully curved, or flatted, or bent to the required forms as shown in the drawings. The edges of all plates and joints shall be planed quite true to the requisite forms and dimensions, so that the edges of the plates may touch each other truly and over the whole surface, and so that the rivet-holes may be set correctly by measurement from the edges only ; and great care must be taken in riveting on the butt plates that the perfect contact of the surfaces may be maintained. The rivet-holes in all wrought-iron plates, angles, and tee- bars are to be carefully marked off in their proper posi- tions with a centre punch, and punched with a nipple punch. No drafting or rimering will be allowed, but the punching must be so accurate that when the work is put together a rivet -J T in. less in diameter than the punched hole must pass easily through all the holes. " All rivet-holes in steel plates, angle, T, H, and C bars are to be carefully marked off in their proper posi- tions with a centre punch, and punched with a nipple punch yiy i n - smaller in diameter than the finished size, and afterwards carefully drilled out to the full diameter shown on the drawings. All burrs left by the drill are to be carefully removed, and all edges of holes in contact with either the head or point of a rivet must be slightly countersunk. At all joints, etc., all rivet-holes are to be punched T 3 ^ in. smaller in diameter than the finished sige, and afterwards carefully drilled out to the full diameter shown on the drawings when the various parts are in position in the work, so that a correct hole is obtained through the several thicknesses of plates, angles, etc., which may be required to be riveted together. " Hydraulic riveting to be used as far as possible. The rivet to be red-hot throughout when inserted, and upset in its entire length, so as to completely fill the rivet- hole. All loose rivets, and rivets with cracked, badly formed, or deficient heads, shall be cut out and replaced by others; and rivets are to be cut by the contractor, and at his expense, whenever the engineer or his representa- tive shall consider it necessary to ascertain that the work is properly executed. When the riveting is done by hand, 96 IRON, STEEL, AND FIREPROOF CONSTRUCTION. it shall be done entirely by the hammer ; the snap is only to be used at the last to give correct form to the rivet head, and must not cut into the iron or steel. " Any of the iron or steel work cracked or split, at whatever stage of the work it may be discovered, will be condemned, and must be removed and replaced by other iron or steel of the specified quality. " Where angles and plates require to be bent, for laps or other purposes, no abrupt or sudden bend or square shoulder likely to crack or injure the iron or steel will be allowed. " The plates and all other iron and steel must be so placed in the work that the fibres shall run in the direc- tion of the greatest strain; the butt plates especially require attention to this. " Any bolts and nuts required shall be cut in a work- manlike manner with a clean and strong Whitworth thread, and shall be made of iron of an ultimate tensile strength of 24 tons per sq. in., and capable of being bent through an angle of 120 when cold without showing any sign of fracture. They must be heated, and dipped while hot into boiled oil. Any bolts passing through waterways are to be galvanised. The whole of the work shall receive a coat of hot boiled linseed oil. Before oiling, the iron and steel shall be well scraped and cleaned from all rust and scales, but the contractor must, as far as possible, keep the work oiled before any rusting has commenced. All surfaces that have to be riveted in contact with each other shall be well oiled before being so riveted, and all surfaces, as well as those concealed from view, the exterior of the work, and all lap joints and angles, must be thoroughly oiled. " The galvanised iron sheets to be No. 16 and 18 B.W.G., riveted at all laps with galvanised iron rivets and burrs, and secured with galvanised f-in. bolts to ironwork, and round-headed screws to woodwork. The sheets to be in the longest possible lengths; all laps and bolt- and screw- holes to be painted with red-lead ground in oil, to secure water-tight joints. The curved corrugated sheets to be bent to shape before being galvanised. The corrugated sheets to be made from soft, fibrous, and uniform metal, perfectly free from laminations, buckles, blisters, and all PRACTICE OF IRON AND STEEL CONSTRUCTION. 97 defects. The sheets to be carefully sheared to dimensions, thoroughly cleaned, and galvanised with the best zinc to the extent of '15 Ib. per foot super, (plain), including both sides. The galvanising is to be well executed, the sheets being drawn through the flux, and all to have two coats of turpentine, both sides, before leaving the manufactory. Samples are to be provided by the contractor on the re- quisition of the engineer, and must stand the Admiralty tests. " The condensation gutters to be Vieille Montagne zinc, No. 16 gauge, 3^-in. girt, with beaded edge and col- lars every 7 ft., with all necessary stopped ends and out- lets, f-in. galvanised iron gas tubing, with tee-pieces and screw caps, to be provided as shown, to take water from condensation gutters into eaves gutters. " The whole of the cast-iron shall be made from the best quality of tough grey pigs, and is to bear a tensile strain of 7 tons per sq. in. of sectional area before frac- ture, and 2i tons per sq. in. of sectional area before loss of elasticity. Two bars are to be cast in a dry mould from each melting, 3 ft. 6 in. long by 2 in. deep by 1 in. wide ; and these, when placed on bearings 3 ft. apart, are to be loaded with a dead load at the centre, and to break with an average of 30 cwt., or a minimum of 28 cwt., and not to deflect less than ^ in. with a load of 25 cwt. The castings are to be true and clean, and free from all defects, and impainted till they have been examined ;. all bolt-holes to be cast of proper size and strength of metal. The cast- iron is to be painted one coat of red-lead ground in oil. " The weights of all cast- and wrought-iron and wrought-steel work have been calculated from the dimen- sions shown on the drawings on the basis of 40 Ib. per sq. ft. 1 in. thick for wrought-iron, 41 Ib. per sq. ft. 1 in. thick for steel, and 37i Ib. per sq. ft. 1 in. thick for cast-iron. An addition of 5 per cent, has been made in the case of wrought-iron and steel to cover rivet heads, and on no account will any additional allowance be made on the weights so calculated. " All pieces of iron or steel work which weigh more than 2 tons are to have their weights plainly stencilled on them in white paint, and with figures not less than H in. high." G CHAPTER X. PRINCIPLES OF FIREPROOF CONSTRUCTION. CONSIDERATION of the manner in which ordinary dwell- ing-houses in most towns are constructed, and of the inadequate provision of good water pressure and other requisites for fire extinction, will in most cases lead to astonishment at the comparatively small number of great catastrophes by fire. It is a fact that the internal ar- rangement of most dwellings, with their floors, ceilings, doors, lathing, skirtings, architraves, and stairs all of wood, affords every facility for the spread of fire after an outbreak has orice occurred. And yet similar construc- tive methods are adopted year after year, and in all prob- ability will continue to be adopted unless legislative restrictions are enforced. Legislation, so far as regards fireproof construction, cannot be said to be over-restrictive in Great Britain. The building bye-laws enforced by most sanitary authori- ties contain only a few requirements as to the position of timbers in walls, or in some cases the provision of party walls carried above the level of the roof ; and the London Building Act, while containing some excellent regula- tions as to roofs, the provision of means of escape, and the position and construction of flues, still falls short of the severity of some of the Continental Fire Acts. For any special regard which is paid to the fireproof construction of large warehouses and other similar structures, the fire insurance offices deserve the credit, as they lay down vari- ous practical requirements which must be followed before the building can be insured at low rates. Without resorting to any expensive methods of con- struction, there are many points in the planning and arrangement of buildings which may be considered with advantage. The popular notion of fireproof construction is confined generally to some form of concrete floor. As a matter of fact, the roof is quite as important a feature. PU1NGIPLES OF FIREPROOF CONSTRUCTION. 09 l a fire should start in the lower storeys of a building provided with the ordinary wooden floors and laths and plaster ceilings, it will, no doubt, make its way with ease upwards ; but in very many cases the fire begins at the top of the building, either by reason of the flames from some adjoining building catching the timber roof -work, or, it may be, by some accidental cause in the upper part of the building. This danger of fire descending is particu- larly liable to arise in warehouses where the stores are inflammable liquids, such as oils, or certain chemicals which will liquefy under the action of heat. One of the most striking instances of this was the destruction of a large warehouse in Berlin a few years ago. The building, six storeys high, was of brick, with so-called fire-proof floors, composed of brick arches between iron girders which were carried by the walls and cast-iron columns. The doors of the separate rooms were of sheet iron. Five months after the building was completed, some temporary openings were made in the floor of the third storey, and, a fire having accidentally occurred, the burning materials fell through to the floor below, setting fire to the contents there, with the result that in five minutes from the time of the outbreak many of the floor arches had collapsed, and in an hour the whole structure was destroyed. Isolation, not only of the building from the neigh- bouring buildings, but of the separate apartments one from another, is one of the chief requirements to be at- tended to. Fireproof construction, in the sense of erect- ing a building which will defy the fiercest fire, is an im- possibility, and the efforts of the architect should be directed to the protection of the building from the attack of fire from outside and the narrowing down of the effects of an internal outbreak by confining the fire to as small a space as possible. With this object in view rooms used for the storage of goods should be kept small, for a large room necessarily means a large fire. Trap-doors from one floor to another should be avoided, and wells for stairs or for lighting should be detached as much as possible from the rooms by walls of fire-resisting materials. Considered solely from the point of view of resistance to fire, the ideal building would be one built of strong brick walls, with roof and ceilings of groined brickwork, 100 IRON, STEEL, AND FIREPROOF CONSTRUCTION. and with openings such as doorways and windows re- stricted as far as possible in size and number. Such a building is, however, placed outside the bounds of practic- ability by reason of its expense, the want of adequate light, and the valuable space occupied by the walls. In special circumstances some approach to this class of work may be possible. In the Bank of England, for example, Sir John Soane constructed nearly all the apartments so as to be fireproof, and without any carpentry whatever in the arches and domes, making use largely of hollow pots or cones of a coarse earthenware. These helped to lessen the weight of materials used without taking away from the strength of the structure. Under the London Building Act of 1894, the following materials are classed as fire resisting : (1) Brickwork con- structed of good bricks, well burnt, hard, and sound, properly bonded and solidly put together (a) with good mortar compounded of good lime and sharp clean sand, hard clean broken brick, broken flint, grit, or slag ; or (b) with good cement; or (c) with cement mixed with sharp clean sand, hard clean broken brick, broken flint, grit, or slag; (2) granite and other stone suitable for building purposes by reason of its solidity and durability; (3) iron, steel, and copper ; (4) oak and teak and other hard timber, when used for beams or posts, or in combina- tion with iron, the timber and the iron, if any, being protected by plastering in cement or other incombustible or non-conducting external coating ; in the case of doors oak or teak or other hard timber not less than 2 in. thick ; in the case of staircases oak or teak or other hard timber with treads, strings, and risers, not less than 2 in. thick ; (5) slate, tiles, brick, and terra-cotta, when used for coverings or corbels ; (6) flagstones, when used for floors over arches, but not exposed on the underside, and not supported at the ends only ; (7) concrete composed of broken brick, stone chippings or ballast, and lime, cement or calcined gypsum when used for filling in between the joists of floors. Without commenting on the above list at present, it will be convenient to summarise here the characteristics of the ordinary building materials considered from the fire-resisting point of view. PRINCIPLES OF FIREPROOF CONSTRUCTION. 101 No material has stood the test of fierce fires better than good brickwork. When all other materials have been either destroyed or distorted so as to be useless, the brick walls have been left standing, although the heat may have been intense enough to vitrify the face of the brickwork. The fire-resisting property of bricks depends chiefly upon the amount and relative proportions of the silica and alumina contained in the clay from which the bricks are made ; the greater the proportion of alumina to silica, the greater is the in fusibility of the clay, although it must be noted that the most refractory bricks are not the strongest for constructional purposes. One great advantage possessed by brickwork is that of comparative freedom from expansion under the effects of heat. It has been calculated that in a 10-ft. length of wall composed of fire- brick, when subjected to a heat of 2,000 F., sufficient to ^ melt cast-iron, the linear expansion is a little more than i in. Terra-cotta is much to be preferred before stone, so far as fire-resisting properties are concerned, as a material for the construction of cornices, panels, and other orna- mental enrichments. In the Cripplegate fire -a few years ago it was noticeable that much of the terra-cotta work had withstood the flames successfully, and seemed none the worse, while of the stone facades almost every stone had split. It is probable that the chief use of terra-cotta in fireproof construction will, however, be not for ornamenta- tion, but as a protective medium for ironwork. In Ameri- can construction, in the tall steel-framed buildings of Chicago and New York, where safety from fire is of the utmost importance, it is used in this direction. The main columns carrying the weight of the whole structure are not cast-iron, but built-up steel stanchions, and to protect these from the effects of fire they are encased, first, in slabs of rough terra-cotta, known as " tiles," 3 in. in thick- ness, and outside this covering there are fixed thick blocks of ornamental terra-cotta which form the exposed face of the columns and the outside shell of the buildings. Another important use of this material is in the con- struction of fireproof floors. Hollow blocks, strengthened with internal ribs, are used to form skewbacks and arches between the iron joists. In a later chapter that will deal 102 IRON, STEEL, AND FIREPROOF CONSTRUCTION^ with the construction of fireproof floors, examples will be given illustrating this class of construction. Although stone of any kind would seem on a first im- pression to form a good material for resisting fire, experi- ence proves that it is far from being reliable under the action of heat. Granites, in particular, although included amongst the fire-resisting materials scheduled under the London Building Act, 1894, are of little value in this respect. The substance of the granite cracks and flies off in small pieces; indeed, a granite pillar 12 in. square has been reduced to sand by an actual fire in a building, while a wooden post standing next to the granite had only been burnt into for a depth of 1 in. Limestones are calcined \>y great heat. Sandstones are found to be the most re- fractory, but even these, when subjected to the heat of a fierce fire and afterwards to a sudden quenching with water, will split and tumble to pieces. In important parts of a structure, such as staircases, any kind of stone is, therefore, inadmissible ; for the merely ornamental fea- tures of outside decoration it may find a use, but it must not be expected to withstand the combined effects of fire and water. Of all building materials, Portland cement concrete is the one which, while having excellent qualities as a fire- resisting material, is at the same time comparatively cheap, and easily adapted to varying requirements. In fact, in the popular sense, fireproof construction identifies itself with " concrete floors," as this is the direction in which efforts have so far been made to obtain immunity from fire. Concrete in itself is well able to stand the effects of intense heat and subsequent quenching with water, and when, in addition to the concrete, there is provided an interlacing system of steel girders or rods, in the manner which will be more fully considered in future chapters, a floor is obtained which may be considered practically fireproof. For stairs, also, concrete, in its various modifications of granolithic, Victoria stone, and other special varieties, affords an excellent material. Plasters of various kinds are little affected by heat. Those having gypsum as a base, such as plaster of Paris, have been used for many years in this connection To still further add to their efficacy, however, they require to be PRINCIPLES OF FIREPROOF CONSTRUCTION. 103 aided by the insertion of wire or metallic lathing. Port- land cement and Keene's cement are to be recommended for forming skirtings or architraves in place of woodwork. A. recent introduction is asbestic, a bye-product from the manufacture of asbestos from serpentine. When combined with a small proportion of lime, it is claimed that a material is obtained which is absolutely fireproof, and one which will not chip or crumble away. Nails can be driven into it and withdrawn with the same facility as in wood- work. One form of its use is in slabs J in. thick, which can be used like wood or screwed or nailed into position. Petrifite, another recent invention, is the name given to a white cement composed chiefly of magnesite, a carbonate of magnesia and one of the constituents of magnesiari limestone. It appears to possess many valuable proper- ties, combining with almost all classes of materials, hard or soft, dirty or clean, to form a very strong substance, which can be applied to surfaces in the same manner as other plasters, or can be cast or moulded into blocks of any size and shape. The woodwork used in ordinary building methods naturally constitutes the chief source of danger from fire. Wooden floors, one above another, with wooden stairs leading from one floor to the next, afford a ready means of spreading the fire when once an outbreak has occurred. When used in sufficient bulk, however, as was before pointed out, wood is capable of withstanding fires which will destroy heavy masonry. A thick mass of woodwork is extremely difficult to burn through, and for this reason a floor composed of planks bolted side by side in any of the methods which will be described in a later chapter, affords a better protection against fire than any construction of iron and concrete. It should be noted that the smooth surface of wrought woodwork does not take fire so readily as does a surface which is left rough from the saw. In many details of ordinary building construction, the position of the woodwork is well controlled by the ordin- ary bye-laws in force. Thus, it is provided that door- frames and window-frames shall be set back at least 4 in. from the face of the building, with the object of prevent- ing them falling outwards in case of fire and spreading the fire to other parts, It is forbidden to carry any wood- 104 IRON, STEEL, AND FIREPROOF CONSTRUCTION. work across a party wall between two buildings, and the Model Bye-Laws provide that not only shall there be 9 in. of brick or stonework between the ends of beams on opposite sides of a party wall, but that there shall be no bond timbers, plates, or plugs built into a party wall. With respect to timber near the flues, it is ordered that no plugs shall be inserted within 6 in. of a flue. The London Building Act, 1894, provides that " timber or woodwork shall not be placed in any wall or chimney breast nearer than 12 in. to the inside of any flue or chimney opening nor in any chimney opening within 10 in. from the upper surface of the hearth." The spread of fire from one storey to another is frequently helped by wood flooring resting on iron girders which are unprotected on the under side from the action of fire, although the space between them may be filled in with some incombustible material such as concrete, or brick arches. The girders in such a case became hot enough to ignite the flooring above. Oak and teak offer considerably more resistance to fire than almost any other timber, and by many architects an oak staircase is considered to be, in case of fire, safer than a stone one. There are many methods of preparing timber so as to increase its fire-resisting properties. They depend mostly on the impregnation of the fibres of the wood with certain chemical salts; for example, Sir William Burnett's sys- tem is to soak the timber for some days in a solution of 1 Ib. of chloride of zinc to 4 gal. of water. Sir Frederick Abel recommends the surface to be painted with alternate coats of silicate of soda and limewash. Phosphate of am- monia, calcium sulphide, iron sulphate, silicate of iron and magnesia, and other salts have all been advocated, but none of these processes have had much practical suc- cess. Several preparations for applying as a paint have been received with favour, notably a preparation known as asbestos paint. Sir Frederick Bramwell, in 1884, at- tributed the saving of the wooden structures of the Inven- tions Exhibition from destruction by fire to the fact that were coated with this preparation. 105 CHAPTER XI. FIREPROOF COLUMNS AND STANCHIONS. THE materials and methods adopted in constructing the columns of a building are of the utmost importance. Columns are subject to the effects of flame on all sides, and the isolated position which they occupy provides an ample supply of air by which the heat is increased. Al- ready subjected, as they are, to the stress of the weights they sustain, it is obvious that, when heated by an intense fire, and afterwards suddenly cooled by water, they are very injuriously affected. It is sometimes wise, therefore, to dispense, as far as possible, with columns, by using beams of a greater depth than would otherwise be re- quired, although this has the disadvantage of being a more costly mode of construction, and of curtailing the head room. The best material to use is undoubtedly good brick- work, as it is least subject to the effects of heat and cold; the amount of space it occupies will, however, militate against its use in many cases. As a rule, cast-iron is the material adopted. As mentioned in the previous chapter, there are certain advantages connected with the use of wooden columns. This material, when sufficiently thick, will withstand fire for many hours, the damage it receives being confined to a reduction of sectional area. Its internal structure is unaltered, and it is not subject to any dangerous degree of expansion or contraction. The amount of damage done to a wooden column can also be readily seen, enabling firemen to work in a building amongst the flames with greater confidence than would be the case where metal columns were in use and liable to collapse without warn- ing. In America, columns of hard pine or oak are largely used in buildings of the factory and workshop class. They are usually of 9 in. diameter or 9 in. square. Care is taken that the timber is thoroughly seasoned, and to 106 IRON, STEEL, AND FIREPROOF CONSTRUCTION. ensure this it is sometimes sawn down the centre, and the two halves bolted together with the central portion out- Fig. 138. Section Cast-iron Stanchions. Fig. 137. Timber Stanchion with Cast-iron Caps, etc. Fig. 139. Ribbed Cast- ; ron Stanchion. side. Another mode of drying the interior of the wood is to bore a H-in. longitudinal hole through the centre of i FIREPROOF COLUMNS AND STANGHIONS. 107 the column, with transverse holes of smaller diameter across the top and bottom. In general practice, no oil or varnish is applied to the outside of any heavy timber for at least three years after it has been placed in the building, so as to avoid the oc- currence of dry rot from the fermentation of the sap in the timber. Cast-iron caps and bases of simple design are also used, as shown in Fig. 137. Columns are generally made of cast-iron, on account of its cheapness and the ease with which the castings can be prepared to suit various requirements. Wrought-iron and steel columns have, however, come into increased use during late years. As a fire-resisting material, cast-iron is very unsafe, as it easily collapses when suddenly cooled by water. In the warehouse at Berlin, referred to on p. 99, the floors were carried by cast-iron columns. After the fire, which only lasted one hour, it was found that out of one hundred columns, thirty-eight had been thrown completely out of position, while thirty-four others, although they remained standing, were so broken or damaged that they were rendered useless. The city authorities of Hamburg some few years ago carried out a series of experiments on the fire-resisting pro- perties of columns of cast- and wrought-iron. The cast-iron columns were 10 ft. 8 in. long, 10| in. diameter, and mostly of |-in. metal. Pressure was applied by a hydraulic press placed below the column, its cross-head being at the top of the column. A hinged oven, containing twelve large gas burners, an apparatus for measuring the heat, and a water jet, was then clamped about the column. After a heat of 1400 F., and a load of 3*2 tons per square inch had been applied, the average result produced deforma- tion in thirty-five minutes. The deformation showed itself by a bulging all round in the middle of the heated part, especially where the metal was thin. With a smaller load, the heat sustained before deformation occurred was correspondingly higher. Jets of water had no effect until deformation heat had been reached. In addition to columns of circular section, those of other sectional shapes are sometimes adopted, as in the cross-shaped column shown in Fig. 138, and the ribbed stanchion shown in Fig. 139. These have little, if any- 108 IRON, STEEL, AND FIREPROOF CONSTRUCTION, thing, to recommend them in preference to the ordinary circular section, except that they are easy to work in with brickwork and joists. They have also the advan- tage of being easily protected from fire by encasing them in cement plastering B (Fig. 139), so as to form a circular column with no iron exposed. The stiffeners or horizontal flanges should have holes cast in them, as shown at A (Fig. 138), in order to form a key for the cement. 140. Round Column Built Hollow. Fig. 141. Square Column Built Hollow. Fig. 142. Hexagon Column Built Hollow. Fig. 143. Hexagon Column Built Hollow. Modern practice has largely adopted the use of columns or stanchions built up of rolled steel or wrought-iron bars riveted together. The forms which these built columns take are almost innumerable. Some of the most typical are those formed from ordinary angles, tees, channels, flats, and girders. Some special sections of iron, such as Z-iron, and Lindsay's angles and troughing, are also made. Some columns are made hollow, as shown at Figs. 140 to 143. It should be noted that a hollow column of wrought-iron or steel is liable to corrosion FIREPHOOF COLUMNS AND STANCHIONS. 1C9 on the inside surface, where it is impossible to paint it after the column has been erected. This defect may be avoided by filling in the interior of the column with con- crete. Pease's tubular construction, which will be found described in Chapter XIII., can also be used for forming Fig. 144. Pease's Triple Tubular Construction. Fig. 145. Pease's Four Tube Construction. columns of an ornamental appearance by combining the tubes in the manner shown in Figs. 144 and 145. The in- terior is filled in with cement concrete, and serves to lock the tubes in place and stiffen the column. The importance of adequately protecting an iron or 110 IRON, AND PlREPtiOOF CONSTRUCTION. steel member from fire depends on the work it has to do, and the consequent destruction which would result from its failure. The collapse of a stanchion would, in many instances, undoubtedly wreck the whole building; in such cases a clumsy appearance must be tolerated in order that ample protection may be afforded. Simply encasing a girder or stanchion with plastering on wire lathing (Figs. Fig. 146. Fig. 147. Fig. 148. Fig. 146. Column Protected with Plaster only : Section. Fig. 147. Stanchion Protected with Plaster only: Section. Fig. 148. Column Encased with Solid Concrete : Section. 146 and 147) cannot be considered an adequate protection in any situation. In Fig. 146, V-shaped pieces of sheet iron F are placed vertically at equal distances apart to block the wire or metal lathing G off the column, leaving an air space H ; by this means a better key for the plaster- ing is obtained. ,o Fig. 149. Fig. 150. Fig. 151. Fig. 149. Stanchion Encased with Solid Concrete : Section. Fig. 150. Hollow Tile Protection to Column. Fig. 151. Hollow Tile Protection to Stanchion. In Fig. 147 light brackets or clips are employed to grip the stanchion and secure vertical wires J in position at the corners, round which the lathing K is strained, L indicating an air space. Figs. 148 and 149 show a simple method of protecting a column and stanchion. The fine mesh galvanised wire netting M is blocked away from FIREPROOF COLUMNS AND STANCHIONS. Ill the surface with pieces of tile N, and the intervening space filled in with fine breeze concrete. In order to get the external surface of the concrete true and regular to receive the plastering, boxes or moulds about 4 ft. long are made and fixed round the column, into which the breeze con- crete is run and allowed to set thoroughly before the next section in height is executed. Porous tile casings, 2 in. to 4 in. thick, are admirable, providing the horizontal as well as the vertical joints are so formed that there is no possibility of the sections being displaced by the fire or the force of a water- jet. Any space behind the tiles should be filled in solid. This Fig. ir>2. Tile Covering for Column. Fig. 153. Fireproof Tiling and Terra-cotta. will not only render the tiles more secure in position, but will prevent^the fire entering tne joints. Such casings must continue from floor to floor, and be independent of any combustible material for support. Fig. 150 shows a tile casing o to a hollow column, and Fig. 151 a tile protection p to a stanchion in which the external diameter is increased as little as possible. There is no difficulty in designing a tile casing for any column or stanchion when the ultimate shape required is known. But as such things are not stocked to any extent, they usually have to be made to order. The tiles are made of various shapes, and many patents have been granted for different methods of combining them and securing them 112 IRON, STEEL, AND FIREPROOF CONSTRUCTION, in place. As a general rule, they are fluted on the outside to form a key for a finishing coat of fine plaster or cement. Fig. 152 illustrates one type in which the tiles are secured to each other by iron pins or dowels, the whole being set in Portland cement, and plastered on the outside. A method of casing in a built stanchion with tiles, and facing it on the outside of the building with ornamental terra-cotta blocks, is shown in Fig. 153, in which r indi- cates the fireproofing, G the terra-cotta, and H the steam- pipes. All ironwork should be free from corrosion when fixed, and be embedded in an air-tight and damp-proof casing. Pipes should not be carried down in proximity to columns or stanchions, but should be arranged side by side in a separate casing or chase, so that, when the front is re- moved, all are exposed, and can be examined and if necessary repaired. Where the casings are likely to be injured by hand trucks or packing cases, ^-in. or f-in. wrought-iron shields should be fixed around them to the required height. Asbestic plasters are frequently substituted for or- dinary plasters, and when laid on a solid foundation they are practically fireproof and waterproof. They are applied \ in. to f in. thick, and, as they are fibrous, nails may be driven into them without injury; but the fact of their taking a considerable time to dry out is often a serious objection to their employment. 113 CHAPTER XII. FIREPROOF FLOORS. FIREPROOF floors have been more elaborated and have received more attention from architects and engineers than any other branch of fireproof construction. This subject has been almost constantly studied since the days when Mr. David Hartley set fire to the lower storey of his experimental fireproof house in the presence of King George III. and the Lord Mayor of London, he and his friends demonstrating their faith in the safety of the structure by remaining in the upper room. This being so, only a few of the typical forms will be dealt with. The iron girders supporting a floor should not be built into the walls at the ends, but should be left free to expand or contract without disturbing the brickwork. For this purpose they are best carrird on brick corbels projecting from the walls. Stone corbels are not so good, as when exposed to fire they split, no doubt as the result of unequal heating. Concrete practically does not expand either under fire or in the process of setting when the floor is being made. In the latter case there may be a slight contraction with a return to the full dimension afterwards, but the contraction does not exceed -^ in. in 30 ft. Iron joists, on the contrary, may expand under fierce heat to the extent of If in. in 10 ft. The expansion in a 10-ft. length of fire-brick flooring under a heat of 2,000 F. has been calculated to be about half an inch. To determine the relative efficiency of different methods of protecting iron joists from fire, experiments were con- ducted a few years ago by Mr. Stanger with three similar sets of 5-in. by 3-in. rolled iron joists, each weighted with 30 cwt. of pig-iron distributed over 8 ft. of their length. One set was embedded in concrete made of Portland cement and sand in the proportions of 1 to 5, to a thick- ness of 15 in. by 7 in. The second set was protected with Doulton-Peto tiles, and covered with concrete (half Port- H 114 IRON, STEEL, AND FIREPROOF CONSTRUCTION. land cement and half sand) ; and the third packed with silicate cotton and cased in a similar cement and in plaster-of-Paris to a depth of 1 in., the sectional area of the whole being 15 in. by 7 in. At 11.22 a.m. the three sets were placed over a furnace having a temperature of 2,000 F. The joists covered with concrete were the first to collapse, dropping down at 1.7 p.m. ; those covered with Doulton-Peto tiles held up till 3.40 p.m. ; but at 6.45 p.m. those covered with the cotton silicate were still unscathed, /A Fig. 154. Asbestos Slabs under a Wooden Floor. the deflection they had made not being \ in. The fire was then left to burn itself out, and, at the end of efeven hours' exposure the silicates were found to be practically un- affected. When iron or steel joists are embedded in cement con- crete, it is not necessary, nor is it advisable, to paint or oil them, as the cement adheres better to the bare iron than it would to the painted surface; and itself forms an efficient protection against rust. In this respect it is unlike lime concrete, which causes rusting to a marked Fig 1 . 155. Asbestos Slabs Between Joists. degree so much so, in fact, that large blocks of stone fastened together by iron clamps set in lime mortar have been forced asunder. One of the simplest and most economical methods of constructing a fire-resisting floor is to protect an ordinary wooden floor with slabs of asbestic plaster or of slag wool (silicate cotton), both of which can be obtained com- mercially in slabs, as cloth, or in the form of loose fibre FIREPROOF FLOORS. 115 or wool. The loose wool is useful for filling up the spaces between the joists as a pugging to deaden sound (as al- ready described), as well as affording protection against fire. A convenient method of attaching the slabs is shown in Fig. 154. The slabs are formed by enclosing silicate cotton between sheets of galvanised wire netting, and are made of thicknesses varying from 1 in. to 3 in. They are secured to the under side of the joists, as shown at A by wooden fillets B B nailed underneath, the nails passing through the slabs. To these fillets are secured the laths, when a lath-and-plaster ceiling c is desired. Additional security can be obtained by placing other slabs between the joists, resting on triangular fillets as shown in Fig. 155. Owing to the comparative cheapness of these methods of construction, and the measure of security they Fig. 156. Solid Wood Floor. afford, they are worthy of more general adoption in dwell- ing-houses and office buildings. Woodwork, when used in solid masses, is an excellent material for fireproof construction. It is extremely diffi- cult to destroy timber in bulk by fire, and in America, partly on this account, and also on account of the cheap- ness of timber, floors and walls are constructed of planks nailed together face to face. The walls of many of the large grain elevators and station buildings are constructed in this way. The system of forming floors by close timber- ing instead of the ordinary use of joists and flooring boards, was introduced into England by Messrs. Evans and Swain between 1870 and 1880. The joists, instead of being placed at some distance from each other, were laid close together, so that air could not penetrate between them, the planks being then spiked as shown in Fig. 156. 116 IRON, STEEL, AND FIREPROOF CONSTRUCTION. As an alternative method, the spikes could be driven in diagonally, and, if thought necessary, the under side of the planks could be protected with a plaster ceiling keyed into grooves formed in the planks. As a test of the capa- bility of this system, a building was erected 14 ft. square inside of 14-in. brick walls, and measuring 7 ft. from the ground to the ceiling. The flooring was laid as described above, of deal battens 7 in. deep by 2^ in. thick, spiked together side by side. One-third of the under side was plastered, the joists being grooved for this purpose ; one-third was plastered on nails partly driven into the planks, and the remaining third was left unprotected. The chamber underneath was packed almost full of timber, which was then lighted, and it was not until after five hours' continuous exposure to the flames that the un- Fig. 157. Hinton and Day's Wood-block Floor. protected portion of the floor gave way. The system was afterwards adopted in large warehouses for the East and West India Docks, London, and in other buildings. A modification of the system just described has been patented by Messrs. Hinton and Day, and is illustrated in Fig. 157. The joists are spaced apart in the ordinary way, but the spaces are filled in with solid blocks, having the grain placed vertically, tongued and grooved together in such a manner that the passage of air between them is prevented. The blocks are carried by fillets nailed to the sides of. the joist. A test of this system of flooring was made at Westminster. Four walls of 9-in. brickwork were erected, and the under side of the floor to be tested was 9 ft. 6 in. from the ground. The lower part of the build- ing was filled three parts full with inflammable material (no petroleum or grease, however), and a fierce fire main- F1KEPMOOF FLOOES. 117 tained for more than two hours, after which it was ex- tinguished, and the under side of the floor was found to be charred to a depth of in. In American factory and workshop buildings a layer of mortar D is often introduced between two thicknesses of flooring as shown in Fig. 158. Here 8-in. by 4-in. wooden joists E support the flooring planks, which are 3 in. thick, on which a layer of mortar, f in. thick, is spread. Floor-boards l in. thick, laid on the top of this, form the working surface of the floor. Sometimes the floor-boards are laid in two thicknesses, crossing each other diagonally, as shown in Fig. 159, in which F in- dicates the layer of mortar. The beams carrying the floors have air spaces round each end, and to avoid the danger of the wall being pulled down by a falling beam Fig 1 . 158. American System of Factory Wooden Floor. Fig. 159. American Floor with Diagonal Double Boarding. in case the latter should be burnt through, the upper end of the beam is cut away at both ends so that it can fall fr-eely. Gypsum Floors. For nearly three hundred years floors have been made with gypsum, or hydrated sulphate of lime, which is the basis of plaster-of-Paris. In Notting- hamshire and Derbyshire, as well as in certain parts of France where the stone abounds, it is gently heated until the combined moisture is expelled. The resulting coarse powder is mixed into a paste and laid over rough boards, or between and over the joists, without the use of floor boards, forming a floor of 8 in. or 9 in. thickness, which sets quite hard in a few hours. As to the merits of this material, opinions differ ; Mr. Hamor Lockwood, who has had a large experience in the construction of fireproof floors, says that it possesses the great disadvantage of not being able to stand either fire or water, and after being 118 IRON, STEEL, AND FIREPROOF CONSTRUCTION. laid down for years will, on becoming soaked with water, expand to such an extent that the building in which it is used is endangered, and so, in case of fire, practically ensures the destruction of the building. On the other hand, in Rivington's " Notes on Building Construction " it is stated that "this substance [gypsum] does, not lose its cohesive power even when it is roasted to a white heat and then drenched with cold water." Brickwork Floors. A common form of fire-resisting floor for factories and warehouse buildings is one made by dividing the floor space into bays, by means of cast- or wrought-iron beams, and then forming arches of brick- work between the beams, the spandrels of the arches being filled up with concrete to make a flat upper surface. At first cast-iron beams of an inverted *T section were used, but these were eventually superseded by rolled iron or Fig. 160. Fig. 160. Brick Arch Floor. Fig. 161. Fig. 161. Blocks to Protect Girders from Fire. steel beams of H section, as shown in Fig. 160. In this floor, it will be seen, the undersides of the girders are exposed to the flame, and a severe fire might cause the floor to collapse. A much better method is to enclose the girders in blocks of terra-cotta or fire-clay, in the manner shown in Fig. 161. The sides of the blocks are shaped to form the springing of the brick arch. In order that the weight of the brickwork may be lessened many forms of hollow bricks have been devised for the arches, but this type of floor as a whole is being generally displaced by more modern forms of greater simplicity. With a view to save headroom, and also to form a flat ground for the ceil- ing on the underside of the floor, many systems of hollow keyed blocks of fire-clay or terra-cotta have been intro- duced. Of these, Figs. 162 and 163 will serve as types. Concrete Floors. Amongst all the various forms of floors made with concrete, alone or in combination with FIREPROOF FLOORS. 119 iron, one of the most satisfactory and simple is that made of large slabs of concrete carried on steel joists, or on beams of concrete. The carrying capacity of such a floor naturally depends upon the quality of the concrete, but when it is found that loads of 14 cwt. per square foot can be carried on floors actually constructed for use, and not merely on experimental slabs, no fear need be felt as to the adequacy of such floors if properly constructed. The cement used should be extremely fine, one practi- cal maker specifying that not more than 10 per cent. Fig. 162. Floor made of Hollow Blocks. shall be retained on a mesh of 14,400 per square inch. The size to which the aggregate should be broken will vary with the thickness of the floor required; for a 6-in. floor, 1-in. gauge will be sufficient, while for a 2-in. floor the aggregate should be of f-in. gauge. In choosing materials for the aggregrate, porous materials like brick, clinker, and coke will be found to require less cement than hard or smooth stones like granite or gravel, but the latter will, of course, resist weight better, and are more suitable for the upper surfaces of the floors. Fig. 163. Hollow-keyed Block Floor. Experiments on the strength of concrete slabs have shown that with 1 part of cement to 6 of aggregate, a slab, 3 ft. 3 in. by 1 ft. 6 in. by 9 in. thick, with the supports 27 in. apart, breaks with 2i tons to 3 tons central load. With 1 part of cement to 4| parts of aggregate, a slab, 2 ft. 6 in. long by 1 ft. 6 in. broad and 6 in. thick, with the supports 18 in. apart, broke with 2i tons central load. With carefully prepared special materials, such as Stuart's granolithic, very much heavier loads can be sus- tained ; thus, tests carried out on floors constructed of this UNIVERSITY 120 IRON, STEEL, AND FIREPROOF CONSTRUCTION. material have shown that slabs of 5 ft. 6 in. span and 2 in. thick will safely carry a load of 5'35 cwt. per square foot of surface. Slabs of 6 ft. span and 3 in. thick carried 14^ cwt. per square foot, while slabs of 7 ft. span and 2^ in. thick carried 11^ cwt. per square foot. Experimental slabs, 19 ft. by 13 ft. by 3 in. thick, carried a load of G 5 tons without breaking. Fig. 164 illustrates one bay of a floor constructed by Messrs. Stuart, and shows the flat slabs 3 in. thick de- signed to carry a load of l| cwt. per square foot. In one direction, rolled steel joists, 10 in. by 4| in., are enclosed Fig. 164. Granolithic Floor. in granolithic to protect them from fire, while in the other direction beams of granolithic, measuring 9j in. by 6 in., are used. Instead of using separate beams of concrete, as referred to in the last example, the beams may be made to form a part of the slab, as shown in Fig. 165. A slab of this description, made of granolithic 3 in. thick and measur- ing 17 ft. 5 in. by 13 ft. i in., bearing on all four sides, carried a distributed load of 23 tons, which is equal to 2 cwt. per square foot. Extending this idea further, there has recently been constructed at the power station of Fig. 165 Granolithic Slab with Strengthening Kib. the Edison Electric Illuminating Co. a concrete floor, 4 in. thick, in one undivided mass, strengthened by ribs or beams cast on the underside. At intervals of 15 ft., beams 18 in. deep by 9 in. wide are formed, running across the building and resting upon supporting piers of brickwork. In the other direction similar ribs are formed 3 ft. 6 in. apart; these being 14 in. deep and tapering from 6 in. to 4 in. in width. As a fire-resisting floor, this appears to be an excellent arrangement, while its cost is said to be less than if iron and concrete had been used in combina- tion. FIREPROOF FLOORS. 121 In cases where a wooden floor is desired over a con- crete basis, it is not always easy to find a satisfactory method of combining the two materials. A common plan is to insert in the concrete, before it is set, wedge-shaped bearers such as are shown in Fig. 166, to which the floor- boards are nailed. An objection to this method is the lack of ventilating space, and, as the bearers are inserted while there is still much moisture in the concrete, there is great danger of dry rot ensuing. This may be avoided by using wedge-shaped bricks of breeze concrete, let into Fig-. 166. Concrete Floor, Boarded. the concrete floor in the same way as the wooden bearers. The bricks are made 12 in. in length, 3 in. broad on the top surface, and 2| in. thick. Of course, they will not rot like wood ; whilst the floor-boards can be nailed to them. Concrete arches, supported on rolled steel joists em- bedded in concrete, form a good floor. This form of construction is shown in Fig. 167. The spans may vary from 6 ft. to 20 ft', or more, according to the quality of the concrete; the rise given to the arches is generally about 1 in. for every foot of span. Mr. Hamor Lock- wood, who has constructed this class of flooring for many Fig. 1(57. Concrete Arches. years, says " it requires no skewbacks, there being no thrusting power as in the case of brick arching; and it can therefore be employed where bricks cannot." This statement is open to doubt, especially when we find a firm of the experience of Messrs. Stuart, the makers of granolithic, providing special arrangements to meet the thrust of such arches. As regards the strength of this form of flooring, some experiments were conducted by Mr. Legg, at the Hackney Town Hall, on a floor 16 ft. 6 in. by 13 ft., divided into three bays of 5 ft. 6 in. span. The 122 IRON, SfEEL, AND FIREPROOF CONSTRUCTION. rise of the arches was 5 in., and the upper surface of the floor was horizontal, the material being 4 in. thick at the crown and 9 in. at the haunches. The girders upon which the arches rested were rolled iron joists 8| in. by 4 in. A stack of bricks, 8 ft. 9 in. long, 4 ft. wide, and 6 ft. high, weighing 6| tons, or 4 cwt. to the super, foot, was sustained for several days without deflection in the arches or girders. With a better class of concrete, such as grano- lithic, much higher results can be obtained. Thus, an arch of 5-ft. 6-in. span, 2 in. thick at the crown, and 7| in. Fig. 168. Concrete Arch with Inferior Quality of Concrete "in Spandrels. at the haunches, carried 6'32 cwt. per square foot. Another, of the same thickness but of i-in. wider span, carried 8*85 cwt. per square foot. One of 9-ft. span and only 1^ in. thick at the crown carried 23'6 cwt. per square foot, and another, 21-ft. 6-in. span and 3 in. thick at the crown, carried 8' 14 cwt. per square foot. An arch of 15 ft. span, with a rise of 18 in. and thickness at the crown of 3 in., broke with a distributed load of 44 cwt. per square foot; and as a factor of safety of 3 may be assumed for this class of floor, 14i cwt. may be taken as the safe dis- tributed load per square foot for this arch. Where there Fig. 169. Concrete Flat Floor. is a great difference in the thickness of the crown and the springing of the arches, the high-class material is used only in a comparatively thin arch, as shown in Fig. 168, the spandrels or haunches being filled in with a poorer quality of concrete. A simple and good style of flooring is shown in Fig. 169, where steel joists are completely embedded in con- crete, and the top surface is finished with a coating of material of finer quality. The sizes and distances apart of the joists will, of course, vary with the size of the FIREPROOF FLOORS. 123 floor and the amount of weight to be sustained, but as a rule they are placed 2 ft. or 2 ft. 6 in. apart. For a safe load of not more than 3 cwt. per square foot, and a span of 12 ft. to 15 ft., steel joists 3 in. by 1^ in. may be used at 2-ft. 6-in. centres, the concrete floor being made 7 in. or 8 in. thick. For spans of 18 ft. to 20 ft. the floors may be 1 in. thicker, and the joists 4 in. by If in. at 2-ft. centres. It is a mistake to look upon the concrete between the joists as being only so much more additional dead weight for the joists to carry : as a matter of fact, the concrete plays an important part in stiffening the girders and so enabling them to carry greater loads with- out deflection. As Mr. Hobbs points out, " a bar of con- crete 3 in. square will break with 3 cwt. when placed on bearings 3 ft. apart ; and a i-in. square rod of iron, with a load of 28 lb., will bend so as to slip between the sup- Fig. 170. Concrete Floor with Iron Bars Embedded. ports. Yet bed the iron in the concrete and it will carry 10 cwt." And again, " a concrete bar 8 in. by 6 in., with 6-ft. bearings, will break with 1,500 lb. suspended from the centre ; put in five pieces of f-in. round steel, well below the neutral axis, and it will carry 9,500 lb." This principle of reinforcing the concrete by the addition of bars of iron or steel of small section has been applied in several ways. Sometimes the rods are simply laid on the bottom flanges of the girders between which they come ; sometimes they are bent round the bottom flanges so as to be secured to the girders. Sometimes they are round in section, in other cases square or twisted. The amount of iron to be used seems to be from ^ to ^ the sectional area of the concrete. The best results are obtained when many bars of small sections are used, instead of only a few bars of larger section ; thus, four bars of 1 in. by $ in. will give greater strength to the floor than one bar 124 IRON, STEEL, AND FIREPROOF CONSTRUCTION. of 1 in. by in., as a greater surface of iron is pre- sented for the adhesion of the concrete. A modification of the above idea is shown in Fig. 170, where the girders are 3 ft. 3 in. apart, with flat bars spanning the spaces between carried on wrought-iron clips. On these flat bars other bars, - in. square, are laid about 9 in. apart, and the whole is then buried in the concrete. On this system, with a span of 12 ft., the joists would be 4-| in. deep, and the thickness of the floor about 8 in. For a span of 20 ft. the joists would be 7 in. deep, and the thickness of the floor about 10 in. Expanded metal (see Chapter XIII.) is an excellent material for use in the manner described above. The lightness of the material and the mechanical bond obtained Fig. 171. --Concrete Floor with Expanded Metal Embedded. in conjunction with the concrete render it valuable for this purpose, and the fact that it is now made in sheets of various sizes up to 16 ft. by 8 ft. allows it to be easily and rapidly laid in position. In 1896 Messrs. Fowler and Baker presented a report on a series of experiments conducted by them on the strength of concrete slabs compared with similar slabs strengthened by expanded metal embedded in them. Summarising these experiments, the report says that the use of ex- panded metal in the case of slabs of 3 ft. 6 in. span increased the strength of a flat concrete slab six to eight times, and, in the case of a 6-ft. 6-in. span, the strength was increased ten and eleven times. Fig. 171 illustrates the method of applying this material. FIREPROOF FLOORS. 12 A well-known system is the one shown in Fig. 172, in which steel joists are placed 18 in. apart, and connected by wrought-iron strips passing alternately over and under the joists, the w r hole structure being then embedded in breeze concrete. Fig. 172. Lindsay's Concrete Floor. A very strong floor for use in warehouses or factories, where heavy loads have to be carried, is formed by using Lindsay's troughing, in the manner shown in Fig. 173. The upper portion of the troughs is covered with con- crete to form the floor, and, in order to protect the under Fig. 173. Lindsay's Trough Flooring. side from fire, blocks of lighter porous concrete are sus- pended by bolts as shown in the illustration at p c. The space between the troughs and the ceiling blocks can be used to accommodate pipes for gas, water, or ventilation. Another large class of fire-resisting floors is based on the Fig. 175. Fawcett's Floor : Longitudinal Section. use of earthenware hollow blocks for bridging the space between the rolled joists. A great many different systems have been put forward, but as the general principle is the same in all of them, it will be sufficient to notice the following : Fawcett's 126 IRON, STEEL, AND FIREPROOF CONSTRUCTION. system, illustrated in Figs. 174 and 175, consists of iron or steel joists, spaced at 2-ft. or 3-ft. intervals, with the intermediate space filled in with earthenware lintels P of arched section, and covered with a layer of cement con- crete. It will be seen that the ends of the earthenware lintels are notched to clip over the bottom flanges of the joists and so protect them from fire. The undersides ot the lintels are recessed in grooves to form a key for a plaster ceiling. Homan and Rodger's floor is very similar to the above, but the earthenware pipes are of triangular section, as shown in Fig. 176. In the " Mulciber " system the space between the joists is spanned by fire-clay blocks, arched on the upper side, Fig. 176. Homan and Rodger's Floor. as shown in Fig. 177. Special blocks are used to cover the lower flanges of the joists. In addition to the systems illustrated above, there are many which may be described as flat arches, formed of separate blocks of earthenware or fire-clay, made in such shapes that, in combination, they mutually support each other, in the same manner as an arch of brickwork. To lessen the weight of the floor each block is made hollow, with internal strengthening ribs. A typical example of this construction is shown by Fig. 163 (p. 119). Pease's tubular construction will be found described in Chapter XIII. For the formation of floors the tubes may be used in the manner shown in Fig. 178, the interior of the tubes being filled in with coke breeze concrete, and FIREPROOF FLOORS. 127 the upper surfaces covered with the same material. With tubes formed of 20 B.W.G. iron, it is claimed that in a span of 10 ft. the deflection is i ii)., with a load of 3 cwt. per square foot. Another modification of the system aims at making the floor not only fire-resisting, but fire- extinguishing. This it is proposed to do by keeping the tubes nearly full of water, at a level maintained by a tank and ball-tap. Short vertical pipes inside the tubes reach above the level of the water inside, and communicate with the open air on the under sides of the tubes. It is expected that the heat of a fire beneath would cause suffi- cient steam in the pipes to extinguish the fire by the escape of steam through the vertical pipe. Only the very best cement, obtained from a reliable Fig. 177. '< Mulciber " Floor. Fig-. 178. Pease's Tubular Floor. maker, should be used for concrete floors, as, if badly burnt or insufficiently ground and air-slaked, it is liable to expand with irresistible force when settling, thrusting the walls in all directions. A wise precaution is to leave a margin all round the walls, to be filled in when the floor has thoroughly set. In one case known to the writer, the only reason that could be assigned for the concrete expanding was the unsuspected presence of a small percentage of lime in the furnace breeze used, which came from a railway yard ; it was found that the engine- men threw lumps of chalk into the fireboxes of the locomo- tives to prevent the fuel they used clinkering badly. Stone templates supporting heavy girders should have their front edges chamfered to prevent chipping, which would happen when excessive pressure, was applied near the edge. l'2S IRON, STEEL, AND FIREPROOF CONSTRUCTION. Terra-cotta lintel floors are convenient to use, as the lintels which span the space between the parallel joists and obtain support on their bottom flanges answer the purpose of centering, as well as providing an admirable surface to receive plastering; but although they do this, they are considerably more expensive than solid breeze concrete floors. The great drawback to lintel floors is that the steel work has to be planned to suit them^the joists must be spaced centre to centre exactly the length of the lintel, which is usually only 18 in. or 2 ft., and they cannot, unless fixed diagonally (which practice in- creases their span), be inserted when the joists are built in ; and should one get broken when concreted over, it cannot satisfactorily be replaced unless the whole bay is cut out. The iron in the clay of which these lintels are sometimes made has been known to turn the plastering which adheres to them a brown tint. These floors are not suitable to use where machinery is working, as the con- stant vibration is found to cause the lips, which project underneath the joists, to break off. It is very doubtful whether they afford the steelwork any better protection from fire than the solid concrete floors in which the joists are embedded. The New York Fire Department tested a floor of lintel construction, and, as a result, found that the tiles cracked and fell away badly under the application of water when at a high temperature, leaving the under side of the joists exposed. In hospitals, solid floors only will probably be employed in the future, as any hollow spaces would har- bour germs if there happened to be any means of access. The lintels usually drop l| in. below the soffit of the joist, so that its lip can pass clear under and protect its bottom flange, and admit a free circulation of air over the whole ceiling. Ventilators may be placed in the ex- ternal walls to assist this circulation ; but if anything went wrong with the under side of the floor, these ven- tilators would act as flues to a fire raging below, and supposing ventilators were not employed, the air, bottled up, overheated, would expand, and burst the floor open. The writer considers that so long as these lintels are made of a material which will not stand the application of water when heated, the solid concrete floor, with hard FIREPROOF FLOORS. 129 cinders and clinkers as a base, which projects 1* in. to 2 in. below the bottom flange of the joists, is a better fire- resisting construction. Hard terra-cottta is brittle, and much less able than the porous article to resist fire or the application of water when at a high temperature. Porous terra-cotta is manufactured by mixing and thoroughly incorporating sawdust or chopped straw with the clay in the proportion of one of sawdust or straw to two of clay. In the burning, the combustible particles of sawdust or straw are destroyed, and cavities remain. A less porous article is made by mixing a small percentage of bituminous coal-dust with the clay. The coal particles must be of a rich quality, as no stain must be left after burning. Porous terra-cotta is a better non-conductor of heat than the hard quality, but it will not support such heavy loads; it is consequently well adapted for column or girder protection, but, owing to the extra labour in- volved in its manipulation before burning, it is more expensive. Portland cement concrete with a stone base is a good non-conductor of heat. Its expansion is slight, and nearly corresponds to that of iron ; but there is no doubt that it is seriously injured by the prolonged action of fire. This can be easily understood, because the water in combina- tionabout 20 per cent, by weight in the form of hy- drates, is driven off, and the adhesive nature of tne cement totally destroyed. A fire has only to continue long enough to completely disintegrate the material. On the con- trary, good, hard, coarse cinder of clinker concretes, pre- ferably without any admixture of sand, resist the action of fire and quenching to a much greater degree. For although the surface in contact with the flames may be destroyed, and a water jet may wash it away to some extent, there is little doubt that the body will remain sound through any ordinary fire, although it may be afterwards necessary to reconstruct it wholly or in part. There is only too much reason to fear that these cinder concretes have a corrosive influence on the iron or steel embedded in them, although to what extent the one or two coats of paint usually applied can be relied upon to counteract this is at present unknown. Good Portland I 130 IRON, STEEL, AND FIREPROOF CONSTRUCTION. cement mortar has been found to preserve iron from cor- rosion, so that if all ironwork were first given a coat of this mortar before the concrete is put in, there is little doubt that it would be perfectly protected from cor- rosion. Limestones used as a concrete base, when in direct contact with the metal, are found to be very injurious, and should not be employed. Four to one is a common proportion for cinder con- cretes, and a top layer, 1| in. thick, of 2 of granite chip- pings to 1 of cement, makes a good floor finish. If it is desired to add sand to the cinders, sufficient must be added to fill the voids, and the proportion would usually be 1 of cement, 2i of sand, and 5 cinders. Waterproof paper on top of the centering boards prevents the escape of water and cement when placed in position, and causes Fig. 179. Section showing- Stirrup Support for Centreing. . 180. Hollow Tile Protec- tion to Coupled Girder. a good hard surface to form on the under side. Good cinder concrete weighs about 80 Ib. per cub. ft., and rough cinder filling about 60 Ib. Fig. 179 shows how the centering is fixed to support a solid concrete floor until it has properly set. Iron stir- rups A, made of 1-in. or f-in. bar, with 2i-in. by i-in. top plate B, are placed round the joists c to support small wood beams or iron joists D, which in turn carry the boards E supporting the concrete. Figs. 83 and 98 (pp. 59 and 68) show the common method of protecting girders with fine breeze concrete. No. 20 hoop-iron is bound round the girder, at distances of 1 ft. or 18 in., and is blocked off flat surfaces by pieces of tile. Rough centering is then fixed, and fine rich concrete rammed well round. When set the centering is FIREPROOF FLOORS. 131 removed, the hoop-iron keeping the sides and soffit in position. In Fig. 83 the coupled girders are spaced apart 3 in., so that concrete can be filled in between them, and so assist to support the wide soffit. If tiles are used as a girder protection, as shown in Fig. 180, they should be mechanically held in position, and not depend on the cement in the joints, because a fire will quickly destroy it and the tiles will fall away. The hollow soffit tile can be held in position by stout hoop-iron passing through it and bent round to grip the bottom flange. In this figure, Q indicates "soffit tile ; R hoop-iron clip ; s cast-iron separator. Figs. 98 and 107 (pp. 68 and 76) show different floor finishes. For wood-block, mosaic, or asphalt, a hard, smooth surface is required. This is usually obtained by Fig. 181. Section of3Floor|in Osborne House, Isle of Wight, erected about 1850. floating the surface of the rough concrete with cement and sand 1 in. thick. For a boarded finish, nailing fillets, 3 in. by 2 in., are embedded in the concrete, 14 in. or 16 in. centre to centre (Fig. 107). By this means combustion would be retarded, owing to there being no air-space round the boards, and no space for dust and dirt to accumulate. An old system of fireproof floor is shown in Fig. 181, ordinary bricks being used to form the arch. When it first came into vogue, cast-iron girders were in use, and later, wrought-iron joists substituted. Fig. 181 repre- sents a section of a floor in Osborne House, Isle of Wight, which was built by the late Thomas Cubitt in 1850, about the time cast-iron girders and brick arches were first used. In any system of arch construction, tie-rods are absolutely necessary; for unless the abutments of the arch 132 IKON, STEEL, AND FIREPROOF CONSTRUCTION. can resist the thrust, it will spread and collapse. If each bay of a floor were always uniformly loaded, the thrusts would neutralise one another, and tie-rods would only be required in the end bays against the walls; but such a condition hardly occurs in practice. The tie-rods in floors are usually f-in. in diameter, and spaced 4 ft. to 6 ft. apart, according to the loads to be carried. The correct position for the rods is in the centre of the skew- back or springing, but this necessitates the rods showing through the soffit, and to avoid this they are, at the risk of faulty construction, often placed sufficiently high to be buried in the arch altogether. In order to secure the ends of tie-rods in walls, 3-in. by ^-in. continuous bond- iron is sometimes built in the walls at the required level all over the building. Formerly, concrete was only put in the spandrils of the half-brick arches for additional A B Fi#. 182. Section of Side and End Construction Hollow Terra-cotta Flat Arches. strength, and the necessity of avoiding all air-space under the finished boarded floorso as at least to retard combus- tion either was not recognised or was avoided for fear of setting up dry rot in the timbers. Nowadays the con- crete, if only very poor stuff, is levelled up above the crown of the arch, and the nailing fillets, with splayed sides, are embedded, and act as screeds for levelling the concrete surface. These fillets are usually placed trans- versely to the joists if the floor is of a double thickness; but if one thickness of boards only is laid, this cannot be done, owing to the desire to run the boards the long way of the room. These fillets are usually spaced 14 in. to 16 in. centres, and are 2i in. wide at tho top, 3| in. at the bottom, and 2 in. thick. If the sides were not splayed they would work loose owing to shrinkage of the timber. The great failing of this type of construction (Fig. 181) is due to the unprotected state of the flanges of FIREPROOF FLOORS. 133 the beams. In order to obtain a level ceiling, binding joists were supported by the girders, and then ceiling joists to receive the lath and plaster ceiling were secured to them. Consequently, there was a large quantity of combustible material placed in proximity to the naked girder flanges and tie-rods. Any type of fire-resisting construction should be judged not so much by its ability to carry heavy loads as with respect to the protection afforded the iron or steel members. A floor of light construc- tion, which might be considered sufficient for dwell- ing-houses and hotels, where the quantity of inflammable material is not great, may be quite unsuited for a com- mercial building where large quantities of highly inflam- mable material are stored. The letter references in Fig. 181 are explained as follows : T binder, u ceiling joist, v sleeper, w floor joist, and x lathing. Fig- 183.- Section of Hollow Tile Segmental Arch. Terra-cotta arches, both flat and segmental, are largely used in America, and they possess the great advantage of requiring only a small amount of water to be used in fixing them; the building consequently soon dries out. It is quite the contrary with solid concrete floors, or composite floors into the construction of which concrete largely enters. Fig. 182 shows both a side construction A and an end construction B flat arch. When the voids in the blocks run parallel to the joists, it is known as side construction ; when at right angles to them, end con- struction. The end-construction arches are found to be nearly twice as strong as the side-construction arches, and will support as much as 15 cwt. to 20 cwt. per ft. super, before failure. The sides of the blocks are splayed parallel to the keystone or skew-back, and not radial, 134 IRON, STEEL, AND FIREPROOF CONSTRUCTION. as would be theoretically correct. If the sides were radial, each block would be different, and the cost of manufacture would be prohibitive. The side-construction arches are more easily fixed than the end-construction arches, and take less mortar in the joints. To economise mortar, some floors have side-construction keystones and skewbacks, and end-construction fillers. A safe rule for the depth of these arches is that the span in feet should not exceed two-thirds of the depth of the block in inches. Blocks are made up to 12 in. deep for side construction, with the maximum span of 7 ft. End-construction blocks are made up to 15 in. deep for 8-ft. spans. Six-inch, 7-in., and 8-in. blocks usually have one, 9-in., 10-in., 12-in. two, and 15-in. and 18-in. three or four interior webs. For segmental arches, such as are shown in Fig. 183, side-construction blocks are employed. The blocks are made 4 in. to 8 in. square, and fixed to break joint. The maximum span these blocks are generally used for is 10 ft., but much wider spans have been employed. Porous blocks are preferred, because, when fitting badly, they are found to rub away and gradually bring more surface into con- tact, whereas solid, hard-burnt blocks chip and crack. The spandril should be filled up with concrete to a level of at least 1 in. above the crown, so that any concussions arising from falling bodies may be eased. The rise of the arch must be at least 1 in. per foot of span. 4 in. blocks are used for spans up to 8 ft. 6 in. ,, ,, ,, 16 ft. 8 in. ,, ,, ,, 20 ft The approximate thrust per lineal foot of brick arches can be found from the formula : 1-5 W L 2 "W = l oac * per sq. ft. in Ib. T = R = rise in inches. L = span in feet. For flat arches take one-half the depth of the arch as the rise. 135 CHAPTER XIII. FIREPROOF PARTITIONS. THE walls which serve to divide buildings from each other, and the interior walls and partitions serving to separate the rooms of a building, are usually of brick- work or wood. Wood partitions may be dismissed at once as a most unsafe form of construction with respect to danger from fire, although something may be done to minimise the danger by the use of special preservative paints or by other methods detailed below. Brickwork affords the greatest measure of safety, but in city build- ings, where land is costly, recourse may be had to plaster partitions of various descriptions on a core of wire-mesh or expanded metal, by which means a considerable saving of space may be effected. It is an essential feature in all party walls that no openings of any kind shall exist in them ; that is, there shall be no doorways or window openings, or apertures of any kind, so that, if an outbreak of fire occurred, it would be confined to one building and not communicated to the next. In many towns it is insisted in the bye-laws that party walls shall be carried up through the roof covering, usually to a height of at least 15 in., measured at right angles to the roof covering, and also that they shall be corbelled out at- the back and front of the building so as to project beyond the gutters and fascias. This is an ex- cellent measure for the prevention of the spread of fire. Where the party walls are not carried up in this way, there is a danger of the flames being blown over the ad- joining roofs, splitting the slates, and exposing the roof timbers to the action of the fire. Other local authorities are content with party walls that are carried up to the underside of the slates ; while in other cases there is no restriction on the height, and consequently rows of cot- tages are built with the party walls extending only to the height of the uppermost ceilings, while the space between the ceilings and the roof timbers form a 136 IRON, STEEL, AND FIREPROOF CONSTRUCTION continuous tunnel along the whole row of buildings. This, it is scarcely necessary to point out, renders it almost in- evitable that a serious fire in any one house will be fol- lowed by the destruction of the entire row. Bond timbers, plates, blocks, or plugs of wood should not be allowed in party walls, all beams and joists whose ends abut upon them being carried by brick corbels. In addition to the carrying up of party walls in the manner described above, it is sometimes ordered that the external walls, when coming within 15 ft. of any other building, shall be carried up to the height of at least 12 in. above the adjoining roof or gutter, so as to form Fig. 184. Lindsay's Cellular Bricks. a parapet wall. In connection with the woodwork at- tached to interior walls, in the shape of skirtings and architraves, it should be pointed out that these form a means of carrying the flames from one part of the build- ing to another, and in many cases they might with advan- tage be replaced by cement, especially in the case of skirtings. In order to lessen the weight of partitions on upper floors, and so reduce the size of the girders required to carry them, bricks of porous terra-cotta are sometimes used. These are made from clay which has been mixed with granular, combustible substances, such as sawdust. The sawdust is consumed in the firing process, leaving the burnt clay thoroughly honeycombed with air cells and spaces. It is of such a consistency that nails and screws FIREPROOF PARTITIONS, 137 can be driven into it, and at the same time it weighs only about half as much as ordinary brickwork. Various forms of hollow or cellular bricks and terra-cotta blocks have also been devised with the view of lessening the weight of such partitions. Fig. 184 illustrates one such system, known as Lindsay's. Internal walls formed with a wood framing may be made fire-resisting by the application of some good plaster- ing, and this method used to be in general use in the houses of Paris. The method of construction, as described in Bree's " Glossary of Architecture," was as follows : " Upon the partition being framed, the spaces between the quarters were filled in with rougn stone-rubble wall- ing, and strong oak batten laths, from 2 in. to 3 in. wide, were nailed up to the quarters horizontally, at distances of 4 in. to 8 in. apart, holding up the stone and prevent- ing it falling out. The next operation consisted in spreading a strong mortar, principally of plaster-of-Paris, over each face of the partition, completely covering- the quartering and laths, and being pressed through from one side to the other. The rubble was completely embedded, and became one mass with the plaster, possessing the stiff- ness and strength of timber with the fireproof qualities of the plaster. Wooden partitions can only be looked upon as in any sense fire-resisting when they are of such a massive con- struction and thickness as to put them almost out of the bounds of practicability, or when they are protected by some such preservative as asbestos paint or some of the processes mentioned in a previous chapter when discussing woodwork (Chapter X.). There are practical difficulties which prevent the general use of chemical solutions im- pregnated into the structure of the wood. For example, the finished woodwork would be damaged in the process, while if the unwrought wood is prepared in bulk it is rendered more difficult to work, and much of the cost of preparation is thrown away on wood which has after- wards to be cut to waste. Of the preservative paints, most are composed of asbestos, mica, borax, soluble phosphates, and tungstates, and similar materials, suspended in or mixed with a solution of silicate of potash or soda. In all such compounds, however, there is a great tendency to 138 IRON, STEEL, AND FIREPROOF CONSTUUCTION blister and flake off on, exposure to the weather. Mix- tures of silicates of lime and magnesia ; of asbestos, chalk, and soluble silicates ; of powdered glass, stone, lime, and silicate of soda : of gelatinous hydrate of alumina, with an alkaline silicate, have all been patented as useful for fireproofing and preserving wood. It was also claimed for petrinte (which does not as yet seem to have been manufactured on a commercial scale) that when it was applied to woodwork the latter was rendered incom- bustible, A fireproof covering for partition walls, cornices, and ceilings can be obtained by the use of materials applied in the form of loose slabs. One of the most popular of these is asbestic, a bye-product from the manufacture of Fig-. 186. Jhilmil Lathing. Fig. 185. Johnson's Wire ' Lathing. asbestos. It is used as a plaster, and, being fibrous and elastic, it does not chip nor crumble away, and nails can be driven into it freely. It is made up, amongst other forms, in slabs in. thick, and it is claimed for these that they can be worked as easily as wood. Salamander is another somewhat similar preparation, having asbestos as a constituent, but is mostly used in the form of em- bossed slabs of a highly decorative character. Petrifite was also used to form slabs coloured and grained to imi- tate marble and granite. Plastering executed on the ordinary wooden laths is readily consumed by fire. Various metallic substitutes have therefore been devised to take the place of laths, and amongst the earliest of these must be counted the invention of Mr. L. Leconte in 1841 for using wire netting in this way, although it is said the invention was not FIREPROOF PARTITIONS. 39 a novelty at the time. The system known as Johnson's patent wire lathing is generally used at the present time. It is illustrated in Fig. 185, and consists of galvanised wire netting of f in. or smaller meshes stretched over strips of varnished hoop-iron about f in. wide. The hoop- iron strips are secured horizontally to upright wooden posts by staples, and are spaced from 6 in. to 9 in. apart. As will be seen from the illustration, the wire netting is spread on both sides of the wooden uprights. In 1889 a large fire occurred at a dye works at Manchester where this system of lathing had been applied, and the super- intendent of the fire brigade reported that it stood the test of a fierce fire and of water satisfactorily, the damage being very slight. Later applications of the idea of supplying a metallic framework for the support of the plaster are jhilmil and expanded metal. The first of these is shown in Fig. 186. It is formed by cutting a series of slits in a thin sheet of iron or steel, and forcing the strips left between the slits in alternate rows upwards and downwards. This affords a good key for the plaster. An invention, which in general principle is very simi- lar to the above, but one which possesses many important advantages over it, is the now well-known " expanded metal " invented by Mr. Golding, of Chicago. The pecu- liar feature of this article lies in its method of manu- facture plain sheets of rolled metal (steel for building purposes) are cut and expanded by machinery into meshes of a diamond shape, the cutting and expanding being done in the one process. The expansion effected in the manu- facture is from two to twelve times the original width of the sheets, according to the size of the meshes and width of the strands formed. In practice the sheets used range from 24 B.W.G. to 4 inches plate, and the meshes are dis- tinguished by the dimension across the shortway of the diamond, such as -^ in., ^ in., f in., f in., 1^ in., 3 in., and 6 in. The strands of the several meshes are varied in section to give a variation in the weight or strength of the material, so that the various requirements of building construction may be met. In Fig. 187 is shown the mode of applying expanded metal to the formation of a fireproof partition in a build- 140 IRON, STEEL, AND FIREPROOF CONSTRUCTION- Fig. 187. Expanded Metal Lathing Par- tition : Elevation . Fig. 183. Perspective View of Fig. 187. FIREPROOF PARTITIONS. 141 ing where the' floors A are carried on wooden joists. Ver- tical tension rods B, of f in. diameter, are stretched tightly between the joists of one floor and those of the floor above, being secured to them by staples and screw-eyes. A ten- sion rod being fixed to each joist, they will, in most cases, be 12 in. or 15 in. apart. The sheets of expanded metal, about 2 ft. in height and 6 ft. or 8 ft. in length, are laced to the tension rods, and the plaster c is then applied to both Fig. 189. Sectional Plan of Partition and Door Jamb. in front of them, and the plaster c is then applied to both sides, forming a partition wall 2 in. or 2i in. in thickness. A perspective view of the same partition is shown in Fig. 190. Details of Tension Hois and Fixings. Fig. 188, and will serve to make clear the method of sup- porting the door frame D by staples E to the tension rods; also the method of applying the lathing to the ceiling. Fig-. 191. Enlarged View of Expanded Metal Lathing. Fig. 189 is an enlarged sectional plan, showing the inter- lacing of the expanded metal between the tension rods; and Fig. 190 illustrates the eyes and screws used for fastening the tension rods at top and bottom. The 142 IRON, STEEL, AND FIREPROOF CONSTRUCTION. peculiar structure of the expanded metal itself is shown in Fig. 191. A curious and decidedly ingenious form of partition wall has been introduced under the name of Pease's Tubular Construction. Split tubes are interlocked into each other by sliding them lengthways, one tube through the slit of another, until they are assembled together in the fashion shown in Fig. 192, which is a plan of the ends of the tubes. By filling up the tubes with cement or fine concrete, they are fixed in position, Fig. 192. Fig. 193. Figs. 192 and 193. Varieties of Pease's Tubular Construction. and a very strong and fireproof wall is obtained. In- stead of filling in the spaces with cement, the smaller spaces only may be filled in with wood F, and a long tie bolt G passed through the tubes in the manner shown in Fig. 193, when the material can be made up into sheets of a convenient size for making portable buildings. It will be noticed in both the above cases that the surface of Fig. 194. Variety of Pease's Tubular Construction. the wall presents a series of vertical crevices, which would afford a very undesirable lodgment for dirt. To obviate this, the construction shown in Fig. 194 has been recom- mended, where the tubes are of two different sizes; and, in addition to filling the interior with cement, it is the practice to plaster over one or both of the faces. Of the strength and fire-resisting properties of this method of construction there can be no doubt, ' 143 CHAPTER XIV. FIREPROOF STAIRS, ROOFS, AND CEILINGS. Stairs. In spite of the fact that in case of fire the stairs afford the only means of escape from the upper floors of most houses, this part of the building is usually so constructed that it is most easily destroyed by fire. When treads, risers, strings, and balusters are all of wood, and very often with the space underneath the stairs enclosed by matchboarding to form a cupboard where boxes and other inflammable articles are stored, the destruction of the whole is almost a certainty should the fire once obtain a hold of the lower part of the stairs. In buildings of the warehouse class the state of things is much better, but in dwelling-houses the usual construc- tion is one which is far from desirable. As this fact has been pointed out, certainly for about sixty years, by various architects and engineers, there is little hope of improvement until legal restrictions are placed upon builders. A more fire-resisting construction would neces- sarily cost more, but even where cost is of little considera- tion, as in the case of large mansions, it is not unusual to find stairs of pitch pine, highly varnished, and, of course, very inflammable. Stone stairs are certainly safer than those of wood, but, as has been pointed out, stone is un- reliable under the action of heat, and it is apt to split. For use in dwellings there would appear to be nothing better than good thick oak or teak, for these woods, al- though liable to be destroyed in a protracted fire, will last long enough to afford time for the escape of the inmates. Concrete, especially in the superior forms of grano- lithic and the allied mixtures, affords a very good material. Ordinary Portland cement concrete, with the aggregate crushed to f in. or i in. gauge, may be used, and it is advisable to insert one iron bar in each step. It is also well to have two or three bars of iron embedded in the concrete through the length of the stairs, that is, 144 IRON, STEEL, AND FIREPROOF CONSTRUCTION. from the top to the bottom. The treads, if left smooth, will be found to be too slippery ; they are therefore usually fluted with a roller, or sprinkled with some fine hard facing spar, which should be rolled into the concrete. Some exceedingly fine stairs have been constructed with granolithic in large public buildings. In the techni- cal schools, Birmingham, a building seven storeys high, a winding stair runs from the top to the bottom of the building, the steps being 8 ft. 6i in. long, and what is known as self-supporting, or built into the wall at one end only. In the Manchester technical school also this material is used for the stairs and landings, the steps being in some cases 13 ft. long. Roofs and Ceilings. The ease with which an ordinary slated roof is attacked by fire from the outside is not sufficiently recognised by most people. While such roof coverings as thatch or tarred felt are obviously combusti- ble, it may be thought that slates afford a fair amount of protection ; but the fact is that slates, when attacked by the flames, split and fall out of position, exposing a mass of woodwork of small scantlings, which are easily burnt; from its position the woodwork of the roof is naturally very dry and combustible. In many districts it is cus- tomary to erect rows of houses with the party walls carried up only to the height of the ceilings of the top floors, so that the space between the ceilings and the slat- ing forms one continuous chamber over all the houses ; in such a case it is obvious that a fire which penetrates to the roof on one house will easily spread through all the rest. The remedy is found in a bye-law compelling all party walls to be carried up through the slating to a specified height above the roof, or, at all events, close up to the underside of the slates. If the roofs of some of our finest public buildings were examined, it would be found that they contain masses of woodwork, which are a great source of danger. The recent destruction of .the Colston Hall at Bristol may be referred to in this connection ; and it was not very many years ago that no less than 20 tons of light, inflammable deal planking was removed from the roof space of the House of Lords. Before describing some of the modern systems of fire- resisting roofs, one curious attempt to solve the difn- FIREPROOF STAIRS, ROOFS, AND CE JUNGS. 145 culty deserves notice. Early in the present century, Mr. Edward Cresy, best known'as the author of the " Encyclo- paedia of Civil Engineering," designed and erected some labourers' cottages of the eccentric form shown in Fig. 195, no woodwork whatever being used in their construc- tion except for the doors. The windows had iron frames, and the floors were of brick arches and cement; but their chief peculiarity was that the walls were carried up in the form of a catenarian arch, meeting at the top, and so forming a brickwork roof. The walls were 9 in. thick, and were covered all over with tiles set in cement. This experiment does not appear to have been repeated by any architect. Fig. 195. Fireproof Cottage with Brickwork Roof. The modern fire-resisting roof is usually flat, formed either with wooden beams boarded and covered with lead, zinc, or some other protective covering, or it is made of concrete similarly to some of the floors described in Chapter XII., but of lighter construction, as it has not the same load to sustain. Flat roofs are useful as play- grounds for children, as drying grounds for laundry work, or, in the case of hospitals and infirmaries, as promenades for convalescent patients, and it is probable that they will be more generally adopted in the future than they are at present. There is some little difficulty in making them water-tight. As concrete alone cannot be depended upon to prevent the rain soaking through, it is usual to cover the roof entirely with asphalt not the builder's so-called j 146 IRON, STEEL, AND FIREPROOF CONSTRUCTION. " asphalt " of pitch, tar, and cinders, but a mixture of, approximately, 10 per cent, of bitumen and 90 per cent, of carbonate of lime. It may be pointed out, by the way, that this has been legally decided to be incombustible. Fig. 196 shows how the asphalt is applied in two unbroken layers of in. thick over a flat concrete roof. A skirting is formed at the parapet wall surrounding the roof, and the asphalt is carried up two or three courses of bricks and tucked into a joint of the brickwork. Water gutters must be formed at an inclination of not less than 1 in 40 to carry off the rain. Vulcanite is used in the same way as the above. It has been recently stated that paper and vulcanite or wood Fig. 196. Flat Roof with Asphalt Covering. Fig 1 . 197. Ceiling of Expanded Metal under Wooden Joists. cement roofs, which are generally employed on the Conti- nent, provide an efficient weather- and fire-proof roof covering when properly laid and suitably covered with earth and pebbles. In public buildings domed roofs have been constructed by interlacing light bars between arched ribs and then embedding the whole in concrete in the manner described in the chapter on fire-proof floors already alluded to. Wooden fillets are embedded in the upper surface of the concrete to receive the slating laths, while the soffit is plastered to form the domed ceiling. When concrete floors are used, ceilings are dispensed with, the under surface of the floor being finished smooth, and plastered to serve as the ceiling. In floors constructed of cellular blocks of terra-cotta or fireclay, grooves are left to form a key for the plastering, as shown in the FIREPROOF STAIRS, ROOFS, AND CEILINGS. 147 before-mentioned chapter on fireproof floors. Wooden floors may be protected on the underside by a ceiling formed of fireproof slabs nailed to, or suspended from, the underside of the joists. Tiles may also be used for this purpose, but are more difficult to fix securely than slabs of silicate cotton or some of the asbestos compounds, which may be obtained in convenient sizes and in artistic designs. The silicate cotton is usually in the form of slabs made by enclosing the material between sheets of wire netting, and it forms an almost indestructible pro- tection. Asbestos may be obtained in various forms, either Fig. 198. Ceiling of Expanded Metal under Steel Joists. as plain sheets of millboard or in the more elaborate forms of Salamander and such like preparations, embossed with highly artistic patterns. Expanded metal, which has been before referred to in connection with fireproof floors and partitions, can be readily utilised for forming ceilings. Applied to a wooden floor, the expanded metal is fastened to the under- side of the joists by nails or staples, and is plastered over, the peculiar formation of the meshes affording an excellent key for the plaster. This construction is shown in Fig. 197. When used in conjunction with steel joists the con- struction is similar to that shown in Fig. 198. Flat strips of iron, known as ceiling bars, are suspended to the bottom flanges of the steel joists by steel clips of the shape shown in Fig. 199, where the end marked A is 148 IRON, STEEL, AND FIREPROOF CONSTRUCTION. bent down after the clip has been slipped into its place. Hangers are used to support the ceiling bars, and clips or Fig. 199. Clip for Fixing Ceiling Bars under Steel Joists. Fig. 200. Method of Fixing Ceiling Bars for Expanded Metal. Fig. 201. Domed Ceiling at the Foreign Office. London. m Fig. 202. Domed Ceiling at His Majesty's Theatre, London. wire to attach the expanded metal to the ceiling bars, and are shown in the enlarged detail at Fig. 200, where FIREPROOF STAIRS, ROOFS, AND CEILINGS. 149 B indicates the ceiling bar and c the floor joist, one lathing clip D being shown open, and the other one E as it appears when bent up to retain the meshing. Johnson's metallic lathing and Jhilmil are also similar materials to ex- panded metal (see page 138). Figs. 201 and 202 show examples of large domed ceil- ings in public buildings, specially constructed to protect the woodwork of the roof. The first of these shows the ceiling over the Cabinet Council Room of the Foreign Office. It is of concrete, having gypsum as a base, and the dome is 36 ft. in diameter, with a thickness of 9 in. at the haunches. The second example, constructed in a similar way, is the ceiling over a dressing-room at His Majesty's Theatre, London. The dome is 30 ft. long, 20 ft. wide, and has a rise of 5 ft. 150 CHAPTER XV. FIREPROOF CURTAINS, DOORS, AND WINDOWS. Curtains. Although the use of fireproof curtains is con- fined to theatres and is consequently of limited intere'st, a few notes on some of the various forms of these struc- tures may be found useful. The curtain is used to fill up the opening of the proscenium so as to divide the audi- torium from the stage, where the greater liability to fire exists. The simplest kind of fireproof curtain is made of two thicknesses of sheet iron, or steel, attached to an iron, framework, the space between the inner and outer sheets being either left empty or filled with some non-conducting substance, such as silicated cotton or asbestos fibre. The curtain is therefore a heavy structure, and has to be counterbalanced in order that it may be easily raised and lowered. Combined with water sprinklers to keep it cool, it is an efficient enough arrangement, but is objection- able on account of its extreme weight and the difficulty of handling it speedily. To overcome these defects as far as possible, Mr. Max Clarke introduced a light iron framework covered with silicate of cotton, which was attached to the framework by wire netting, and covered on the outer side with canvas painted as a drop scene. Various forms of curtains have also been devised with asbestos cloth stretched on a framework of iron, one of the latest of these being at " Olympia," where four large screens made of Danville asbestic, each measuring 130 ft. by 90 ft., have been erected. A curtain introduced by Captain Heath was made of canvas with a backing of spongy asbestos, and designed to be kept wound on a roller below the level of the stage. Beneath this roller was a long trough of water, contain- ing another roller, under which the curtain passed when being unrolled. To the top of the curtain was attached a counterbalance weight which, being released on an alarm FIREPROOF CURTAINS, DOORS, AND WINDOWS. 15] of fire, pulled the curtain upwards over the proscenium opening, the curtain being saturated with water when it arrived in position. Another novel form of curtain was patented by Mr. E. W. Stead, and introduced at the Theatre Royal, Hali- fax. It is composed of two sheets of iron T ^ in. thick, and placed 3 in. apart. The curtain is divided horizon- tally into two parts, the top half being moved upwards and the lower half downwards. The upper half is the heavier, and is connected by steel ropes and pulleys to Fig. 203. Figs. 203 and 204. Sheet-iron Doors. th(3 lower half in such a way that its weight serves to keep the curtain closed. When it is desired to open the cur- tain, water is let into a tank attached to the lower half until it is heavy enough to descend, pulling up the upper half. In case of fire, the outlet valve of this tank can be opened, discharging the water, and closing the curtain in about thirty seconds. The proscenium opening measures 21 ft. 6 in. by 21 ft. 4 in., the top curtain weighing 38 cwt., and the bottom curtain and tank 35 cwt. Doors. The requirements of a fireproof door are : that it shall be capable of withstanding great heat, shall completely fill the opening in which it is fixed, and shall '152 IRON, STEEL, AND FIREPROOF CONSTRUCTION. be closed easily, preferably by automatic means. Such doors are usually made of sheet iron riveted to a frame- work of angle iron and T-iron, or, in some cases, to thicker strips of flat iron, used as stiffeners. Fig. 203 is an illustration of a simple sheet-iron door with the edges strengthened by angle irons, riveted on, and T-iron diagonals. The door frame is of cast-iron for building into a wall. Fig. 204 shows a door stiffened by flat bands. This door would be more easily warped under the influ- ence of heat than that shown in Fig. 203. Doors of either of these descriptions should be provided in duplicate Fig. 205. Fig. 206. Figs. 205 and 206. Corrugated Iron Doors. that is, one fixed on each face of the wall, separated by a space of the thickness of the wall. In case of fire, one door may be heated to redness, and even considerably warped, without the other one suffering any damage. To decrease the weight, corrugated iron is sometimes employed, especially in large sliding doors such as those shown in Figs. 205 and 206, where the frame is of angle and T-iron and the doors slide on rollers in the one case at the top, and in the other case at the bottom, of the door. In all fireproof doors that are hung on hinges special care must be taken to insure their security by fastening FIREPROOF CURTAINS, DOORS, AND WINDOWS. 153 them with strong bolts, both to the doors and to the walls or frames. The latches, being also subject to heavy wear, should be strong. One of the most efficient kinds of fireproof door is made of wood encased in sheet steel. Two thicknesses of tongued and grooved boards, preferably of oak, cross each other diagonally, and are nailed together. They are then entirely covered with thin sheet steel, which completely protects the wood from contact with air ; by which means, however great may be the heat, the wood cannot burn, and immunity from warping is attained. Fig. 207. Sliding- Door on Inclined Fig. 208. Arrangement for Guides. Automatically Covering Crevices at Bottom of Door. Doors intended for strong-rooms are usually both fire- proof and burglar-resisting, and are of the nature of safe doors. They are of double construction, hung in iron frames, the intervening spaces between being generally filled with some non-conducting substance. In the case of sliding doors, provision should be made for closing up, as far as possible, the spaces left be- tween the edges of the door and the wall. The top, and one edge of the door, are often made to fit into channel- iron grooves. Where a groove is also formed in the floor for the bottom of the door to run in, it is advisable to have a strip of wood to fit into it, and so protect it from being accidentally clogged with dirt. This bottom groove may 154 IRON, STEEL, AND FIREPROOF CONSTRUCTION. be dispensed with by hanging the door on a sloping guide, as shown in Fig. 207. When the door is pushed back, it rises clear of the floor ; when closed, it rests upon the floor, and forms a tight joint. With hinged doors, or doors hung on pintles, good joints round, the two sides and the top can be easily insured, as the door is usually fixed in an iron frame. At the bot- tom, however, a certain amount of clearance has to be given to allow the door to open freely, and in order to close this crevice, the ingenious device shown at Fig. 208 is sometimes employed. It consists of an angular closing Fig-. 209. Cast-iron Window Sash. piece hinged on pins at each end, and, when the door is open, lies with one face flush with the surface of the floor. The lower pintle of the door carries an arm, which is fixed at right angles to the face of the door in such a manner that when the door is closed tnis projecting arm pushes up the angular closing piece into the position shown in the illustration, and the space below the door is effectually guarded. Arrangements for automatically closing doors are very desirable. One of the simplest and best systems applic- able to sliding doors depends upon a fusible alloy melt- ing at a temperature of 160 F. The door is hung upon an inclined guide, and is prevented from closing by means of a round stick about 1 in. in diameter, which reaches across from one edge of the door to the opposite side of the door frame, as shown in Fig. 207. This stick is divided diagonally at the centre, and a ferrule, made of two pieces of copper soldered together longitudinally with FIREPROOF CURTAINS, DOORS, AND WINDOWS. 155 the fusible alloy, covers the joint in the stick. When this ferrule is exposed to a temperature of 160 F., it yields and splits open, causing the stick to separate, and the door to close by its own weight. To prevent the stick from falling in the way of the door, and to allow of the latter being shut at any time, the stick is connected to the top of the door frame by small chains at each end. Various other arrangements of wires or chains to hold back the doors, or with counter-weights to close the doors where Fig. 210. Fig. 211. Figs. 210 and 211. Cast-iron Window Sashes. they are not hung on inclined guides, have been used, in which the melting of a specially provided portion of the wire or chain causes the doors to close automatically. Windows. Up to the present time little attention seems to have been given to the protection of window open- ings, which consequently offer a ready means of spreading a fire. Iron shutters of simple construction, and so ar- ranged as to be easily closed, afford an efficient protection ; revolving shutters, such as are used for shop "fronts, are also good if kept in working order. Cast-iron window frames and sashes, such as those shown in Figs. 209 to 211, 156 IRON. STEEL, AND FIREPROOF CONSTRUCTION. are in regular use, but, although fireproof, they do not prevent the breaking of the glass under intense heat, and the consequent passage of the flames. It should be noted that when the panes of these iron sashes are small, it is impossible to rescue anyone by way of the window, and cases have occurred where lives have been lost in this way. Glass is now made containing a wire mesh embedded in its substance, and is said to stand under great heat with- out falling to pieces. INDEX. American Building Laws with Re- gard to Stanchions, 25 Fireproof Floors for Factory, Angles, Lindsay's, 108 Angle Steel, 94 Arches, Concrete, for Fireproof Floor, 121 Asbestic, 103 Covering for Fireproof Parti- tions, 138 Fireproof Curtain, Danville, 150 - Plasters, 112, 114 Asbestos Paint, 104 Bases for Built Steel Stanchions, 31, 32 Cast-iron Column, 24 Stones, for Foundations, 42 Bases of Columns, 14 Beam Grillage, Foundation, Steel, 39 , Obtaining Moment of Resist- ance of, 74 , Rectangular, Moment of Iner- tia of, 74, 75 Beams with Distributed Loads, 66, 67 Bolts, 49 for Ironwork, 49 , Length of, 49 , Minus Threaded, 58 , Plus Threaded, 58 Bramwell's System of Fireprooflng Timber, 104 Breaking Strength of Cast-iron Columns, 19 Bree on Fireproof Partitions, 137 Breeze, Coke, 68 , Furnace, 68 Bricks, Fletton, 25 Brickwork Fireproof Floors, 118 , Fire-resisting Property of, 101 Building Laws in America with Regard to Stanchions, 25 Built Columns, 108 Steel Stanchions, 30 , Formula for, 30, 31 Built-up Stanchion, 18 Burnett's System of Fireproofing Timber, 104 Caps of Columns, 14 Castings for Building Work, 11, 12 , Examining, 13, 14 , Thickness of Metal in, 14, 15 Cast-iron Columns, 11, 23, 24 , Breaking Strength of, 19 , Experiments on, 107 , Fire-resistance of, 107 , Safe Load of, 23 Cast-iron, Stilting for, 51 , Weight of, 47 , Wood Pattern for Mould- ing, 12 , Contraction of, 15 , Rusting of, 15 , Safe Resistance of, 92 Stanchions, 10, 11, 22, 23 , Square Stilting with Lugs, 52, 53 , Tensile Strength of, 97 , Window Sashes, 155, 156 Ceilings, Fire-proof, 146-149 , Silicate Cotton for, 147 Cement, Keene's, 103 , Portland, 103 Cinder Concretes, 131 Clarke's Fireproof Curtain, 150 Coke Breeze, 68 Colours representing Metals, 9 Columns, Bases of, 14 Built, 108 Caps of, 14 Cast-iron, 11, 23, 24 Breaking Strength of, 19 Experiments on, 107 Fire-resistance of, 107 Safe Load of, 23 Stilting for, 51 Weight of, 47 Wood Pattern for Mould- ing, 12 Cross-shaped, 11, 107 Fireproof, 105-112 Foundations for, 42-44 Gordon's Formula for, 21 Hexagon, 108 Hollow, 108 , Areas of, 18 , Tile Casing to, 111 Loads on, 43, 44 Pease's Construction of, 109 Protected with Concrete, 110 - Plaster, 110 Round, 108 Solid Steel, Strength of, 39 Square, 108 Steel, Formula for, 31, 33 , Supporting Three Floors, Strength of, 21 Testing Thickness of, 13 , Wooden.Advantages of, 105. 106 Compound Girders, 59 , Moment of Inertia of, 75, 76, 78 Concrete Arches for Fireproof Floor, 121 Base for Wood Fireproof Floor, 121 158 IRON, STEEL, AND FIREPROOF CONSTRUCTION. Concrete Fireproof Floors, 118-125 for Fireproof Stairs, 143 , Portland Cement, as a Fire- resisting Material, 102 for Protecting Stanchion, 110 Connections for Girders, 50 Joists, 61, 62 Continuous Girder, Stilting for, 54 Corrugated Iron Fireproof Doors, 152 Countersunk Rivet, 57 Coupled Girders, 59 Cranked Joist for Stairs, 79-81 Cresy's Fireproof Cottage, 145 Cross-shaped Columns, 11, 107 Crushing Resistances for Timber, 93 Cup-headed Rivet, 56 Curtains, Fireproof, 150, 151 Danville Asbestic Fireproof Cur- tain, 150 Deflection of Girders, 60 Drawing Parabola, 68, 69 Dome Elliptical, Framing for, 89-92 Doors, Automatically-closing, 154 , Fireproof, 151-155 Elliptical Dome, Framing for, 89-92 Evans and Swain's Fireproof Floor, 115, 116 Expanded Metal Fireproof Ceil- ings, 147, 148 Floors, 124 Partitions, 139-141 Factory, American Fireproof Floors for, 117 Fawcett's Fireproof Floor, 125, 126 Fidler's Formula for Struts, 18 Fireproof Ceilings, 146-149 , Expanded Metal, 147, 148 Columns, 105-112 Construction, Principles of, 98 Cottage, Cresy's, 145 Curtains, 150 , Clarke's, 150 , Danville Asbestic, 150 , Heath's, 150 , Stead's, 151 - Doors, 151-155 - Floors, 113-134 , American, 117- of Brickwork, 118 - of Cinder Concretes, 130 of Concrete, 118, 125 Arches, 121 , Evans and Swain's, 115, 116 - of Expanded Metal, 124 for Factory, American System, 117 , Fawcett's, 125, 126 , Fowler and Baker on 124 , Granolithic, 120 , Gypsum, 117, 118 , Hartley's, 113 Fireproof Floors, Hinton and Day's Wood Block, 116 , Hobbs on, 123 , Homan and Rodger's, 126 , Lindsay's Concrete, 125 , Trough, 125 , Lockwood on, 117, 118 , " Mulciber," 126 -, Pease's Tubular, 126, 127 - of Portland Cement, 129 , Stanger's, 113 , Stuart's, 120, 121 , Terra-cotta Arches for, 133, 134 , - - Lintel, 128, 129 - of Wood with Concrete Base, 121 Partitions, 135-142 , Asbestic Covering for, 138 , Bree on, 137 , Expanded Metal, 139-141 , Golding's Expanded Metal for, 139 , Jhllmil Lathing for, 139 , Johnson's Wire Lathing for, 139 , Leconte's, 138 , Lindsay's Cellular Brick, 137 , Pease's Tubular, 142 , Petrifite for, 138 , Salamander for, 138 - Stairs, 143-144 , Concrete for, 143 Windows, 155, 156 Fire-resisting Floor, Constructing, 114, 115 , Strengths of, 64 , Making Timber, 104 - Materials, 101-104 , London Building Act and, 100 - Roofs, 144-146 , Flat, 145 , Vulcanite, 146 Flask, Moulding, 12 Flat Fire-resisting Roof, 145 Fletton Bricks, 25 Floor Joist, Support for, 76 with Joists and Girders. 72 and Roof, Knee Girder Carry- ing, 85-89 : of Turret, 85 Floors, Fireproof, 113-134 (see also Fireproof Floors) , Fire-resisting, Constructing, 114, 115 , , Strengths of, 64 on Ground Level, Prices for, 68 - of Solid Wood, 115 , Three, Steel Columns Support- ing, 33 Formula for Built Steel Stanchion, 30, 31 , Fidler's (see Fidler) , Gordon's (see Gordon* INDEX. 159 Foundations for Columns, 42-44 . Columns, Base Stones for, 42 , Maximum Loads on, 42 , Portland Cement Concrete for, 42 - for Stanchion, 42, 43 f steel Beam Grillage, 39 Fowler and Baker on Fireproof Floors, 124 Framing for Elliptical Dome, 89-92 Furnace Breeze, 68 Girder, Compound, 59 , Compound, Moment of Iner- tia of, 75, 76, 78 1 ( Weight of, 47, 48 Connections, 50 , Continuous, Stilting for, 54 , Coupled, 59 , Deflection of, 60 , Fixing, in Wall, 72 , Formula for Deflection of, 77 and Joists Encased in Con- crete, 68 , Knee, carrying Floor and Roof, 85-89 , Moment of Inertia of, 75 Girders, Pocket Supports to, 53 , Weights of, 47, 48 Golding's Expanded Metal Fire- proof Partition, 139 Gordon's Formula for Columns, 21 Solid Rectangular Pillars, 28 - Struts, 18 Granolithic Fireproof Floor, 120 Gypsum Fireproof Floors, 117, 118 Hartley's Fireproof Floor, 113 Heath's Fireproof Curtain, 150 Hexagon Columns. 108 Hinton and Day's Wood Block Fireproof Floor, 116 Hobbs on Fireproof Floors, 123 Hollow Columns, 108 , Areas of, 18 Homan and Rodger's Fireproof Floor, 126 Ironwork, Bolting up, 49 Jhilmil Lathing for Fireproof Partitions, 139 Joggle and Cleated Joints for Joist, 61, 62 Joint for Joists, 61 Johnson's Wire Lathing for Fire- proof Partition, 139 Joist Connections, 61, 62 Joints, American Laws for, 63,65 for Stairs, Cranked, 79-81 Joists "and Girders, Safe Loads on 66-78 , Joggle and Cleated Joints for 61, 62 , Joggle Joint for, 61 - for Landing for Stairs, 82 , Lengths of, 60 , Moment of Inertia of, 75 , Notched and Cleated Joints for. 62 Joists, Rolled Steel, 30 , Rolled Steel, Labours on, 63 , Steel, Square Stilting for, 51, 52 , Table of Strengths for, 64 , of Trimming for Skylight, 83, 84 Keene's Cement, 103 Knee Girder carrying Floor and Roof, 85-89 Labours on Rolled Steel Joists, 63 Landing for Stairs, 82 Leconte's Fireproof Partition, 138 Lindsay's Angles, 108 Concrete Fireproof Floor, 125 Trough Fireproof Floor, 125 London Building Act and Fireproof Construction, 98 Fire - resisting Materials, 100 Loads, Beams with Distributed, 66, 67 on Columns, 43, 44 Lockwood on Fireproof Floors, 117, 118 Machine Riveting, 55, 56 Metal, Expanded, for Fireproof Floors, 124 Partitions, Expanded, 139-141 Metals, Colours representing, 9 Minus Threaded Bolt, 58 Moment of Inertia of Joists and Girders, 75 Rectangular .Beam, 74, 75 Moreland's Steel Columns, 37, 39, 41 Moulding Cast-iron Column, Wood Pattern for, 12 Flask, 12 "Mulciber" Fireproof Floor, 126 Notched and Cleated Joints, 62 Paint, Asbestos, 104 Pan-headed Rivet, 57 Parabola, Drawing, 68, 69 Partitions, Fireproof, 135-142 (see Fireproof Partitions) , Wooden, 137 Party Walls, 135, 136 Pease's Construction of Columns, 109 - Tubular Fireproof Floors, 126, 127 - Partitions, 142 Petrifite, 103 - Covering for Fireproof Parti- tions, 138 Pillars, Wrought-iron, Gordon's Formula for Solid, 28 Plaster as a Fire-resisting Material, 102 for Protecting Column, 110 Plasters, Asbestic, 112, 114 Plates, Punched, Diameter of Rivets in, 54 , , Riveting, 55, 56 Plus Threaded Bolt, 58 Pocket Supports to Girders^ 53, 160 IRON, STEEL, AND FIREPROOF CONSTRUCTION. Porous Tile Casings, 111 Portland Cement, 103 Concrete as a Fire-resist- ing Material, 102 for Foundation, 42 Fireproof Floors, 129 Ribbed Stanchion, 107 Rivet-holes, 95 Riveting Gang, 57 , Machine, 55, 56 Punched Plates, 55, 56 Rivets, 54-58 , Countersunk, 57 , Cup-headed, 56 , Head, Bearing Surface of, 57 , Heating, 57, 58 , Pan-headed, 57 in Punched Plates, Diameter of, 54 , Snap or Button, 56 , Steel for, 94 Rolled Steel Joists, 30 Roofs, Fire-resisting, 144-146 (see also Fire-resisting Roofs) Rusting of Cast-iron, 15 Steel, 15 . . . Wrought-iron, 15 Safe Load on Cast-iron Column, 23 Loads on Joists and Girders, 66-78 Salamander Covering for Fireproof Partitions, 138 Silicate Cotton for Fireproof Ceil- ings, 147 Skylight, Joists for Trimming for, Snap 'or Button Rivet, 56 Solid Steel Columns, Strength of, 39-41 Wood Floors, 115 Specification for Engineering Work, 93-97 Square Columns, 108 Stairs, Cranked Joist for, 79-81 , Fireproof, 143, 144 , Landing for, 82 Stanchions, Built Steel, Base for, 30 , Built-up, 18 , Cast-iron, 10, 11, 23 , Cast-iron, Square Stilting with Lugs, 52, 53 , Designing, 16 , Foundation for, 42, 43 Protected with Concrete, 110 , Ribbed, 107 , Weights of, 45-47 Stanger's Fireproof Floor, 113 Stead's Fireproof Curtain, 151 Steel, Angle, 94 Beam Grillage Foundation, 39 Columns, Formula for, 33 , Moreland's, 37, 39, 41 , Solid, Strength of, 39 Supporting Three Floors, Steel, Expansion of, 10 - Joists, Rolled, 30 , Square Stilting for, 51, 52 , Rivet, 94 , Rusting of, 15 , Safe Resistance of, 92 , Tensile Strength of, 94 Stilting for Cast-iron Column, 49 Continuous Girder, 54 , Square, 51, 52 , Square, with Lugs to Cast-iron Stanchion, 53 Stone as a Fire-resisting Material, 102 Struts, Fidler's Formula for, 18 , Gordon's Formula for, 18 Stuart's Fireproof Floor, 120, 121 Tensile Strength of Cast-iron, 97 . steel, 94 Terra-cotta, Fire-resisting Proper- ties of, 101 Lintel Fire-proof Floors, 126, 127 Threads, Whitworth, 58 Tile Casing to Hollow Column, 111 Tiles for Protecting Girders, 131 Timber, Bramwell's System of Fireproofing, 104 , Burnett's System of Fire- proofing, 104 , Crushing Resistances for, 93, , Fireproofing, 104 , Stanchion with Cast-iron Caps, 107 Trimming for Skylight, Joists for, 83, 84 Turret Floor, 85 Vieille Montague Condensation Gutters, 97 Vulcanite Fire-resisting Roof, 146 Walls, Party, 135, 136 Weight of Wrought-iron, 45 Weights of Stanchions, 45-48 Whitworth Threads, 58 Window Sashes, Cast-iron, 155, 156 Wire Lathing, Johnson's, for Fire- proof Partition, 139 Wood Pattern for Moulding Cast- iron Column, 12 Wooden Columns, Advantages of, 105, 106 Floors, Solid, 115 Partitions, 137, 138 Woodwork, Bye-laws on, 103, 104 -, Danger of, 103 as Fireproof Material, 115 Wrought-iron Columns, Experi- ments on, 107 Expansion of, 10 Pillars, Gordon's Formula for, 28 Rusting of, 15 Safe Resistance of, 92 Weight of, 45 PRINTED BY CASSELL & COMPANY, LJMITKD, LA BELLE SALVAGE, E.G. 14 DAY USE RETURN TO DESK FROM WHICH BORROWED LOAN DEPT. This book is due on the last date stamped below, or on the date to which renewed. Renewed books are subject to immediate recall. MAY 3 196? 1 1 1 MAY 2 9 67 'Hi * M ' * J5 LD 21A-60m-2,'67 (H241slO)476B General Library University of California Berkeley YB 51933