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Whenever possible, these have been omitted from filming / II se peut que certaines pages blanches ajouties lors d'une restauration apparaissent dans le texte. mais. lorsque cela itait possible, ces pages n'ont pas k\h filmies. Addittonal comments / Commentaires suppl^menlaires: Th(» h«m \% film« signifie "A SUIVRE". Ie symbols ▼ signifie "FIN". Les eartaa. planchaa. tableaux, etc., peuvent Atre flimte i dee taux da rMuction diff«rents. Lorsque Ie document est trop grsnd pour itre reproduit en un soul ciich*. il est film* A partir da I'angia supArieur gauche, de gauche A droite. et da haut an bas. an pranant la nombre d'imagae nAcessaire. Las diagrammas suivants illustrant la mAthode. 1 2 3 1 2 3 4 5 6 MKaooorr MMumON tbt omit (ANSI and ISO TEST CMAIIT No. 2) 1.0 1.1 lis 2.2 m riu u IM US 1210 1.8 t&tim A dE^y^JyHGE Inc ISU (Ml Mdin SIrMt '-iiT> ft The Elizabethtown Bridge Vi p.»?.' H. G. TYRRELL Chief Engineer jTWI L w^m ^,_^ jf- ii^ ■ ; L- V ii.i-isil*>f>i ^-'^iK-T ;'i5s^> * 1 i'- ■*^S^i{,?^*?^,T!Q?' ^- ■■.*-.*■'*'_ ■'■" -" ' *"-j'T-' .- 1 1 ^^V^^^^^^l The EJizabethtown Bridge Highway Bridge over The Miami River at EHizabethtown, Ohio The Longest Sininlc-Tritts Span Price $1.00 DESIGNED BY H. G. TYRRELL. CHIEF ENGINEER u u J u H d z u s M SB p !2 a H H a r-* «• INTRODUCiiON THIS account of the design an'' construction of the Eliiabethtown bindge, baa been prepared in response to numerous inquiries. Several years hfve elapsed since the bridge was completed and until now time has not permitted me to write any desr iption. Brief mention of he work hta been made in several of the iechnieal joomala, «mong which are The Iron Age. The Canadian Engineer, The Railway and Engineering l^view, and others. No comorehen- sive description has, however, appeared. Little or no mention is made in this description of the inspection, tests or erection, nor is there any sheet of details included. As the bridge is the longest truss bridge span in exiatence, it will continue to be of special interest, at any rate until such time as its length is exceeded. It is possible that at .some future time, the account may be revised and enlarged. H. O. TYRRELL. Evanston, Illinois, February, 1909. Copyright, 1909, by H. G. Tyrrell Highway Bridge over the Miami River at Ellizabethtown, Ohio THIS bridge is remarkable in being the longest simple- truss span in existence. It has a span of 586 feet be- tween centers of end pins and surpasses in length by 36 feet the longest other span, which is one in the bridge crossing the Ohio River at Cincinnati, known as the Cincinnati and Covington railway and highway bridge. The Old Bridge. On the site of the present new steel bridge, there had been for many years an old covered wooden bridge, known locally as "Lost Bridge." It consisted of three spans, 195 feet long each, supported on stone piers and abutments. The old piers were unusually heavy, and yet, notwithstanding this fact, the foundation beneath them was badly scoured, so much so that one had fallen several feet out of plumb at the top. The superstructure of the old wooden bridge was also rapidly failing, and the spans showed excessive sag, a condi- tion frequently developing in old wooden bridges before fail- ure. In the summer or autumn of 1903 the superstructure of the old bridge was destroyed by fire, and the need of replacing it at once became apparent. Type and Length of New Bridge. In selecting the most suit- able type of bridge for replacing the old one, there were numer- ous important considerations. The rise and fall of the water in the Miami River is very uncertain. At flood seasons it rises rapidly, sometimes 20 feet or more in a few days. The greatest difference between high and low water is about 30 feet. At such times the last ten feet or more of rise is back water from the Ohio River. For this reason all bridges in this district are built at about the same elevation of 30 feet above low water of the Ohio River. The railroads and many of the highways Description of Highicay Bridge are likewise built on banks at the same elevation, for at Hood seasons the entire country around is liable to be covered with water. At another river crossing, about a mile distant from Eliza- bethtown, the conditions had been met in previous years by building a suspension bridge of 500 feet clear span, spanning the entire width of the water course. The suspension bridge is quJtt an imposing structure and an ornament to the district, but is lacking in the more important l-equirement of rigidity. It has a clear i-oadway of 20 feet and the stone towers at either end are placed 36 feet apart, so the cables have a considerable cradle. It has, also, six sets of stay cables from the towers to the floor, and is braced laterally by three sets of rod guys at each end, fastened to stone blocks on the river bank, yet the passage of ordinary loads, such as farm wagons, causes excessive vibrations. In high, or even moderate winds, the swaying of the bridge is also considerable. At New Baltimore, Ohio, in the same county, similar condi- tions had been overcor by building a single truss span 465 feet in length, which was described in Engineering News, October 16. 1902. The railroads were also having difficulty with their bridges in the saine region, and some such bridges were destroyed by having their piers undermined by the scour and wash of the uncertain currents and soil. At the time when the rebuilding of the Elizabethtown bridge was being considered, a railroad bridge in the vicinity was being strengthened and the piers protected at great expense, by having large quantities of broken stone and loose rock deposited around the piers and abutments. It was found, however, that notwithstanding the dumping in of many carloads of rock, and the strengthening of piers with additional concrete, the river piers were still in an uncertain condition and frequently exposed to the damag- ing influences of scour and the shifting of the channel. For these reasons it was decided to avoid the use of river piers in rebuilding the bridge at Elizabethtown, and to bridge the entire waterway with a single span. Having thus decided on the use of a single span, approximating 600 feet in length. fl* Elisabethtoirn, Ohio it then bei-anie necessary to select the most suitable type of bridge. The suspension bridjie described above is in some respects very desirable, but on account of its lack of stitYness was not seriously considered as a type for Elizabethtowu. The under- neath clearance would not permit the use of a deck arch of so long a span, and a through arch, such as those used at Bonn or Dusseldorf, or more recently at Bellows Falls. Ver- mont, are lacking in lateral stitTness. In through arches such as those mentioned above, it is necessary, in order to maintain the required clearance through the bridge, to omit top lateral bracing between the arch ribs for some considerable distance back froir the springs. This is more serious than in truss bridges, where the end posts incline at an angle of 45 degrees or more with the horizontal. With the through arch the slope of the ribs is so gradual that a large part of the most etVective lateral bracing between the ribs must necessarily be omitted. Some forms of stiffened suspension bridge, and a cantilever design of 600 feet span between piers, with back stays similar to the back stays of a suspension bridge, were also considered. None of these forms were favored, chiefly because of their lack of stiffness. Of the alternate forms considered, the cantilever above referred to would doubtless have given the best results. It would leave the waterway entirely free of piers and would permit the use of a narrower roadway, by placing the tnisses further apart at the short, than at the end of the cantilever arms. It is interesting to note that a bridge of this type has since been built at Long Lake, N. Y., and is described in the Engineering Record of September 29, 1906. After due consideration of various types, it was decided to use a through, pin connected, simple-truss bridge. Invitation for Tendon. The bridge was being built by Ham- ilton County, and advertisements were therefore printed, call- ing for separate tenders for substructure and superstructure. The advertisement gave the length of span as 586 feet between centers of truss bearings and called for competitive plans and hi '-; to be submitted. 10 Description of Highway Bridge Substructure Tend«n. In response to the advertisements, tenders for building and repairing the substructure were re- ceived from five competing firms, which are given below: No. 1 No. 2 No. 8 No. 4 No. 5 Forming bank, cu. yd.. 1 .35 $ .30 1 .40 1 .40 1 .38 Excavation, per cu. yd. 1.50 .90 1.00 1.00 .90 Crushed atone, pr cu.yd 1.80 1.20 1.80 1.80 1.75 Screenings, per cu. yd. 1.80 1 20 1.80 1.80 1.75 Lumber, per M 60.00 40.00 60.00 40.00 40.00 Rolling, per sq. yd ... . .05 .01 .05 .05 .05 Piling, per lin. ft .50 .37 .50 .30 .50 Concrete, per cu. yd . . . 9.00 10.00 8.00 8.00 8.00 Sheet piling, per M 15.00 10.00 15.00 13.00 12.40 Bridge seat beams . . . . 1500.00 1000.00 1495.00 600.00 1500.00 Steel rods, per Ih .04 .035 .05 .03 .045 Puddling, per cu. yd. . . 2.00 2.00 2.00 2.00 2.00 The foundation work consisted chiefly in repairing the old stone abutments by building up new material in reinforced concrete in front of the old stone work, carrying up the retain- ing walls and parapets, and rebuilding the bridge seats with lines of steel beams embedded in concrete. As this part of the work presented no unusual difficulty, or was not of particular interest, details of the substructure are not given. It will be interesting, however, to note that the presence of the old piers was some considerable assistance dur- ing erection. The steel work was assembled and erected on timber false work at low water season. SupMratructiire Tenders. Competitive plans and prices were received from eighteen diflferent firms for the design, con- struction and erection of the superstructure, with the result that the design prepared by the writer wa« accepted and the contract was awarded accordingly. Description of Accepted Design. In preparing a design sev- eral comparative estimates were made, diflfering principally in the depth of truss, number of panels, design of floor system, and live loads, A summary of these estimates s.i follows: at EtUiaietktown, OMe 11 OffinpuntiTe EitimatM for EUnbethtown Bridge. No. of WUthof DmmI Uwd Uv« Uwl StMl Eatinuitad Coat PtanPUMla Boul Joiat vmttu POT ft. tona Coat phu86» A 23 30' 10"I'a 2' apart 8,480 2.400 920 868,000 $86,000 B 22 30' 12"rB 3' apart S.710 1.200 686 53,000 <«.200 C 18 30' l"l'm 3' apart 2.304 1.000 360 39.700 49,600 D 18 30' 3"xl4''3'apart 2.122 1,000 514 37.700 47,100 E 18 80' 15"I's 6' apart 2,368 1.000 554 39,600 49.400 F 18 30' 15"rs 3' apart 8.442 1,000 604 41.900 52.400 O 24 30' lO'Ts 3' apart 8.438 1.000 607 42.800 68.600 H 24 30' 12"rs 6' apart 2.488 1,000 591 42.500 68.100 K 24 30' 6"ra 3' apart 2.445 1.000 601 43.400 64,200 L. 18 30' 7"r« 2.5'ap't 2,590 1.000 643 45,200 66,600 M 24 35' 10" I'» S' apart 3.600 1.600 867 68,900 86.100 N 24 35' 3,144 1.000 769 60.900 76,100 O 1£ 35' g'Ta 3' apart 3.092 1,400 713 57,300 71.600 P 24 30' 10" r« 2' apart 2,826 1,000 710 50,400 63,000 The center truss depth in all designs from A to L, inclusive, vfds 80 feet ; also for design P ; while M and N are 87 feet, and O, 75 feet deep. In designs K, J d O, it will be seen that six- or seven-inch steel joist are u- while in all other designs much larger beams are required. The ability to use smaller joist is plainly due to the shorter panels of the floor system. Comparative estimates were made to ascertain the relative economy between using a larger number of short truss panels and a smaller number of longer truss panels, with intermediate floor beams in each panel, carried on heavy side girders. The comparisons clearly showed the economy of longer truss panels. Design L was therefore selected as providing the economy of long panels in the trusses and at the same time short panels, and corre- spondingly small joist for the floor system. Diagrams 7 to 12 inclusive, illustrate the various designs considered by the writer, No. 12 being the selected one. and the outline on which the bridge is built. The width selected for the roadway was 30 feet, and as the end posts and top chordr- are 30 inches wide, the distance between centers of trusses is 32 feet 6 inches, which is one-eighteenth of the entire span. The trusses are 18 Description of Highway Bridge divided into 18 panels, 32 feet 6 inches lung each, making square panels fur the lateral system. The type of truss is the subdivided Pratt, with main panels 65 feet long. The depth of truss varies from 80 feet at the center to 40 feet at the first panel point. The curve of the top chord is a paiabola, in straight sections of two panel length. Stiff laterals and sway bracing are used throughout. This is a very essential feature of the design, and one upon which much of the stiffness of the bridge depends. Lateral and other light struts are built in l)OX f rm, latticed on all four sides. The first panel of diag- onals in the top lateral system are built in the same way. Each of the 32-feet-6-inch panels of the floor system are again sub- divided by carrying an intermediate floor beam on two longi- tudinal beams, one at each side of the bridge. In addition to the benefit of economy in floor framing, the two side beams serve also as chords for the lower lateral system. The longi- tudinal and cross floor beams are of the same size, and diagonal laterals are rigidly connected by plates, which fasten to the bottom flanges of both cross and longitudinal beams. The floor joist consist of 6-inch steel beams, spaced 2 feet 6 inches apart, elevated on 9-inch beam corbels. On the steel joist is laid the 2%-inch oak flooring, spiked to six lines of 3x7 oak spiking pieces, with 60d nails. The wheel guards are 6x6-inch oak, beveled on the inner edge and elevated on 4 inch blocks, spaced 2 feet apart for drainage. The bridge was given an initial camber at the center of 3 feet. On each side of the roadway there is a neat railing, made of four angles latticed in box form. This railing lines up with the inner face of the web posts and fastens to them. The portal, as shown on the writer's design, is a heavy lattice framework, but it was changed in the shop to one of plate construci.on. This change was plainly a mis- take, as it does not in any way harmonize with the light fram- ing of the bridge. The lack of harmony of the portal with the rest of the bridge shows very clearly in the photographic view. The two side lines of heavy floor stringers, which act also as wind trass chords, are rigidly attached by means of bottom bracket angles to the main truss posts. Such portions of the wind chord stresses a8 are not resisted by these longitudinal at Eliznbethtnini, Ohio in » side beams, are transferred to the bottom ehord eye bars, through these rigid connections. The cross beams, at the panel points, are suspended by two rod hangers 1\_^ inches in diameter each, fnmi the bottom chord pins, and at the same time they are riveted to the ')ottom angles on the web posts. This gives a rigid floor beaui connec- tion and at the same time reduces the cost of erection. At one end of the bridge are sets of turned rollers, and at both ends the heavy side beams are connected to the shoe boxes, thereby transferring the wind strains as directly as possible to the masonry. The vertical posts are spliced at the joints of the lateral struts. The minimum thickness of metal used is one-quarter inch. The metal throughout is medium steel of 60.000 to 68.000 pounds per square inch tensile strength, ciinforming to the Manufacturers' Standard Specifications. The following is a detail estimate of the material in the superstructure : StMl Pound* Staal poands per lin. ft. Joist 185.000 315 Floor beam and hangers 83,000 142 Bracing 203,000 345 Railing 20.500 35 Shoes 24,000 4 1 Trusses 769,000 1,312 Total steel 1,284,500 2.190 Lumber 54,000 feet, board measure Loads. The assumed dead load per lineal foot of bridge used in determining the stresses, was 2,900 pounds. This in- cludes the weight of all steel and lumber, and 300 pounds per lineal foot for snow and ice. The snow load causes no vibration or impact and was therefore classed as dead load. The effect however on the web members of a partial snow load, was con- sidered and provided for. Wet lumber was assumed to weigh seven pounds per foot board measure. Seven-tenths of the t-> J«y f f »9F* {. 2 ^ « i .^ N Q Ji*' rt ^t* ff/ w/ ••» 1 *•' » -f «• »••*• ^r-r^ /^T *r » j*j «»:^ J/ . j» (9 k ^ T/' Hi X 25 W s S\ (3 // Q 4 V| > « >. N A& J isrf J **/ - st'i^jrJW^ ^ rj'A^*iy' TT" j>^ J . N J» «. n 1 * 1 * i < i VI #->•»« AT ^^ 3 it • • 1 • J- I ii /.-.J sv. 1 f < 4 ***J ^^ v^ 1 « I s /i IN^ 1 r» •- -" • 1 ^ ' • • •» \ 2^ ! It « > 4 1 j...t.vS:< V t. jr ^^ 1 4^ ^ —WW i y^ ^K> / !1 ti(n i^ K 51 I xx » 1] \ ii^ ^\ ;; ? p. Nh / \\ ft /_^ ■5 7 III .11 i 1 ?! \ :: ' .^ -^' 7 y^ ! ^j ^ ij \J^T[ J - !i / vi. 7 X "^ 1 •' \ A "^A-/ ^/ 7 ^ /fe ! : \.=-' ^; ; » - — V p* — \ 16 Ihmriptiun of Hhjhiniy Bridge entire dead load whh HHNiiined um Hctiiivt at points of tho bottom chord, and tin* n-niaining thnt'-tenthM at the ijointu of the top chord. The assumed live h)ad was l.(MX) pojinds per lineal foot of bridge, for the tnwseH, and for the tloor and its Mupports 70 pounds per wjuare foot of roadway, or a ten ton road roller or wagon. Them- loads are all in siddition to the weight of snow and ice as described above. The wind load was taken at HO pounds per square foot of exposed surface. After the completion «»f the bridge it was the intention to remove the two river piers, one of which was already leaning over and in danger of falling. The accompanying stress sheet shows the maximum stresses in the various members for dead, live and wind loads, and the sizes and sections used. The coefficient diagrams show the stress in the various members for panel loads of unity. (Competitive Designs. Diagrams Nos. 1 to 6, inclusive, show the truss outlines for some of the designs submitted by other engineers and bridge companies. All outlines having 22 panels or more in the trusses have evidently an excessive number of web members for economy. Number 5 has too shallow a truss, while No. 6 is too deep. Number 6, with panels 48 feet in length, was designed for a heavy system of floor framing, somewhat similar to the accepted design No. 12, excepting that in place of rolled beams for the main floor supports, plate girders were used. Each panel then became a plate girder span 48 feet in length and 30 feet in width, with several intermediate floor beams carried on the heavy side plate girders, the cross floor beams supporting steel joist. The weight of the floor system in No. 6 is excessive, due to the unusual length of truss panels. Those truss outlines have a better appearance where the curve of the top chords is uniform from end to end between the upper ends of end posts. The break in this curve at the second panel points in the upper chord, as shown in diagram No. 2, is unsightly. Number 5 has the appearance of being too flat over the central panels of the top chord. at KUzahrthtnirn, Ohio 17 Tabto of Long Ipan BridgM For the pun*"**" "' conipariHon. a table of other long upan bridgea is given, arranged in the order of their length. Rhrar Ciond Miami Ohio Ohio Ohio Kind of 9Mf Railwmy or hivhwar ft Eniii 19M Bliaabathtown 188f> Clnoinaati 1894 LuuiiTille 1889 Cincionati 18M Philadelphia Delaware 1880 Pittdbarg Ohio St. Louie 1885 HendenoD 1880 Ceredo Cairo Havre de Grace lim Cincinnati 1870 Kuilenburg IMS New Baltimore 1800 Saltaah 1880 Hawksburjr 1901 Hamiltra Miami Highway Railway and Highway Railway Railway and Highway Railway Railway Miwiaeippi Railway Ohio Railway Ohio Railway Ohio Railway Suaquehanna Railway Ohio Railway Leek River Miami Taular Highway Railway Railway Highway B86 H. O. Tyrrall B60 Wm. H. Burr 5M Phwnii Bridge Co. MS 533 683 5M 58S Keystone Bridv « 5tl T. K. Tbomaoa 590 Union Bridge Co- 516 515 J. U. UnTille 515 G. Van Dieeen 465 J. H. Hilton 456 Brunei 416 Union Bridge Co. 406 The Miami empties into the Ohio River below the City of Cm- cinnati It will be seen that many of the longest spans are over the Ohio and its tributaries. In the tributaries near their mouth the high water conditions are similar to those of the Ohio River itself. Snpantructtire gpeeifloationi. The following are extracts from the general specifications under which the bridge was built: 1. Headroom.— The bridge shall have a clear headroom of not less than 14 feet. 2 Material.— AU framing of the bridge shall be made of wrought steel, of the grade known as Medium Stee', with an ultimate tensile strength of from 60,000 to 68,000 pounds per IS .'^/Vtf-i4 XZ /^/V/VJ 2o >*»/e/v/Vi 2o ^/^A/£-^S /S /«»^. /^2 3 /2 /^/Vifzj. J ^ ^9^fA» 'MmM. 8 x^ ^/9/^ri* Z 2 ^yf/^Sa 2 Z /'./A.-. /8 ^/f^^ii /O Jl /2 io Description of Highway Bridge square inch, and an elastic limit of not less than one-half the ultimate strength. 3. Flooring.— The flooring sha; consist of a single thickness of oak plank. laid crosswise of the bridge and at right angles to the center line. It shall be laid in two lengths, meeting at the center, where it shall be spiked to two lines of wood joist, and the joints in the plank flooring covered by a longitudinal oak timber, dividing the width of the bridge into two separate driveways. The plank shall have a thickness not less than one- twelfth of the distance between joists. At either side of the bridge there shall be oak wheel guards not less than 4x6 inches, set up on oak blocks spaced not more than five feet apart! These wheel guards shall be bolted securely through the floor- ing with iron bolts with washers. 4. Loads.— In addition to the dead load of material in the bridge, it shall be proportioned to sustain a moving live load of 1,000 pounds per lineal foot of bridge and an additional load of 300 pounds per foot for snow and ice. This latter may be considered as dead load. The structure shaU be propor- tioned for a wind load of 30 pounds per square foot, acting on the exposed surface of both trusses, and all bracing that is likewise exposed to wind pressure. 5. Unit Stresses, follows : The permissible unit stresses shall be as TMsion: pwiq. ft. Tension In eye ban. jj.ooo jl """'""" i Tension In laterals 20.000 ""''"'"° ' Tension for combined dead, live and wind '°a«>» 25.000 Tension In bottom flanges of solid rolled ''^a^s 12,500 at Elisabethtoim, Ohio Pound* per sq. in. iVtmprpMHioii: * lateral strutB P=13.000 - 60 ChordB, live loadH P=1 2.000 - r.5 Chords, dead loads P=24,000 - 1 10 Web poats. live loads F=10.000 - 45 Web posts, dead loads P=20.00« - 90 Ib the above, P is the allowable stress per square inch in pounds. L is the length of member in Inches, r is the least radius of gyration in inches. No compression member shall have a Icn^h exceeiliiifj; KM) times its least radius of gyration f«»r nmin members, or 120 times for lateral struts. The maximum allowable shearing stress on rivets, holts ami pins shall not exceed 10,000 pounds per square inch, the l»ear- ing stress shall not exceed 20,000 pounds per s(|uare inch, and the bending stress 25.000 pounds per stjuare inch. Connections for field rivets shall have 25 per cent more rivets than rtMpjired by the above allowable units for shop rivets. 6. Details of Construction. — Eye bars shall be so made that in testing they shall break in the body of the bar rather than in the head. Welding will not be allowed in the body of the bar. Holes shall be bored in the center of the head, and on the center line of the bar. All bracing throughout shall be capable of resisting both tension and compression. In proportioning the sizes for lati'ral bracing, both systems shall be considered acting at the same time, the compression pieces resisting up t»» their safe capacity, and the balance of stress being carried by the tension member. Deftcription of Highwny liridge The upper lateral struts shall be the full depth of upper chord hikI slinll he rigidly attached thereto. The lower lateral diag- onals shall be connected at the panel poi* ts of the truss so that stress components from the lateral system shall be transmitted to the main truss chords. The floor beams shall be so attached that there will be no tendency towards rotation alH»u1 the chord pins. Overhead cross sway bracing shall I.e placed at the trus.s panels and this shall be as deep as head room or proper truss connections will permit. It shall be all stiflf bracing, and where lu'cessary, provision shall be made in the vertical chord posts ari