& s'/^-iy iUNIVERSiri , Cornell University Library TG 310.C77 General specifications for s^^^^^^^ 3 1924 004 638 734 "The most perfect system of rules to insure success must be interpreted upon the broad grounds of professional intelli- gence and common sense." GENERAL SPECIFICATIONS FOR STEEL RAILROAD BRIDGES AND VIADUCTS. NEW AND REVISED EDITION, 1906. By THEODORE COOPER, • ~ Conpuiting llngineer.. By THEODORE OOOPER, M., Am. Soe. C. E. Specifications for Steel Railroad Bridges, 1901, 1906. $0 50 1890, 1896. 25 Highway Bridges, 1901, . 50 ii|90, 1896. 25 Specifications for Foundations and Substructures of Highwayand Electric Railway Bridges, illustraited, I9b2, . . . . , . . • • V • 1 00 American Railroad Bridges, cloth, . ■ • • „• 2 00 « « II IC ^ (I It FOR SALE :5Y . . ENGINEERING NEWS PUBLtSHING COMPANY 220 Broad wa^TjNe^w York. Sent by Mail, postpaid, on receipt of price. PREFACE. The author's first railroad bridge specifications were pre- pared over a quarter of a century ago. From time to time these have been revised to meet the requirements of increas- ing train loads and the improvements in material and methods of construction. This edition is the tenth revision, seventh of those published in his own name. While these specifications are " general " in their require- ments, they are more especially intended to cover ordinary railroad bridges or those resting on two supports only. For special structures or those having special or unusual condi- tions and requirements, they should be supplemented by clauses suitable for the particular case. Specifications have no executive functions. Unless intel- ligently supervised and executed, they have little value. The author's experience forces him to the conclusion, that plans and structures fully complying with the specifications are limited in number; many are defective in important details. We are now at a period, when railroads will demand bridges capable of carrying the maximum possible train loadings, not only safely, but rigidly. There will be here- after no increasing train loads to cover or excuse the faults of design, details of construction or inferior material. Bridges of the future must be relatively better than those of the past. Any false economy by scrimping the details or using an inferior class of material will not redound to the credit of the Bridge Engineer. N. B. — The author cannot undertake, through correspondence, to discuss, explain or instruct in regard to the use of these specifications. Copyright by Theodore Cooi'KK, Consulting Engineer, 45 Broadway, New York. General Specifications for Steel Railroad Bridges and Viaducts, SEVENTH EDITION. 1906. GENERAL DESCRIPTION. 1. All the structures shall- be of wrought steel, as specified. (§§ 133-148) Cast-iron or cast-steel may be used in the machinery of movable bridges and in special cases, for bed-plates. 2. The following kinds of girders shall preferably be Kind of Girders. employed: Spans, up to 20 feet .... Rolled beams, or longitudinal trough floors. " 20 to 75 " .... Riveted plate girders. " 75 to 120 " ... .Riveted plate or lattice girders. 120 to 150 " .. . Lattice or pin-connected trusses, over 150 " ... .Pin-connected trusses. Generally " double track through " bridges will have but two trusses, to avoid spreading the tracks at bridges. In calculating strains the length of span shall be under- Length of Span. stood to be the distance between centres of end pins for trusses, and between centres of bearings for all beams and ' girders. 3. The girders shall be spaced, with reference to the axis spacing of of the bridge, as required by local circumstances, and directed by the Engineer of the Railroad Company. (§5.) Longitudinal floor girders shall in no case be less than three feet and three inches from centre line of tracks for single track bridges, or one-half standard distance centre to centre of tracks for double track bridges. (§ 6). Head-room. 4. For all through bridges and overhead structures there shall be a clear head- room of 21 feet above the base of the rails, for a width of six feet over each track. Clear width. S- In all bridgcs thc clear width from the centre of the track to any part of the trusses shall not be less than seven (7) feet between the heights of two feet and fifteen feet above the rails where the tracks are straight, and an equivalent clearance where the tracks are curved. [The additional clearance required on curves for passen- ger cars, 57 feet c. to c. of trucks and 80 feet over all, will be as follows : For curvature, 0.85 D inches on each side ; 1.7 D inches between tracks, where D equals degree of curve. For elevation, the clearance at top of the car on inside of curve must be increased 2^ inches for each inch of track elevation.] 6. The standard distance, centre to centre of tracks on straight lines, will be feet for R. R. Trestle Towers. J. Each trcstle beot shall, as a general rule, be composed of two supporting columns, and the bents united in pairs to form towers ; each tower thus formed of four columns shall be thoroughly braced in both directions, and have struts between the feet of the columns. Transversely the columns shall have a batter of not less than one horizontal to six vertical for single track, and one horizontal to eight vertical for double track. The feet of the columns must be secured to an anchorage capable of resisting double the specified wind forces. (§§ 25, 27.) Trestle Spans. 8. Each towcr shall have sufficient base, longitudinally, to be stable when standing alone, without other support than its anchorage. (§§25, 27.) 9. Tower spans for high trestles shall not be less than 30 feet. ' 10. Unless otherwise specified, the form of bridge trusses ,ro™^o« may be selected by the bidder ; for through bridges, the end vertical suspenders and two panels of the lower chord, at each end, shall be made rigid members. In general, all spans shall have end floor beams for supporting the stringers, (§ 14.) ; and all floor beams shall be riveted to the posts and vertical suspenders, above or below the pins, (§ III), or to the chords. 11. All lateral, sway and portal bracing must be made of Lateral Bracing, shapes capable of resisting compression as well as tension, and must have riveted connections. (§§ 33, 40, 83). 12. The wooden floors will consist of transverse ties or Wooden Floor. floor timbers ; their scantling will vary in accordance with the design of the supporting steel floor. (§15.) They shall be spaced with openings not exceeding six inches, and shall be notched down ^ inch and be secured to the supporting girders by |-inch bolts at distances not over six feet apart. For deck bridges the ties will extend the full width of the bridge, and for through bridges at least every other tie shall extend the full width of bridge for a footwalk. 13. There shall be a guard timber (scantling not less than Guard Timbers. 6 x 8") on each side of each track, with its inner face parallel to and at feet inches from centre of track. Guard timbers must be notched one inch over every floor timber, and be spliced over a floor timber with a half-and-half joint of six inches lap. Each guard timber shall be fastened to every third floor timber and at each splice with a three- quarter (I) inch bolt. All heads or nuts on upper faces of ties or guards must be countersunk below the surface of the wood. (§ 65). 14. The guard and floor timbers must be continuous and properly supported over all piers and abutments. 15. The maximum strain allowed upon the extreme fibre Allowed strain of the best yellow pine or white oak floor timbers will be °" 1,000 pounds per square inch. The weight of a single en- gine wheel may be assumed as distributed over three ties, spaced as per § 12. 16. The floor timbers from centre to each end of span must be notched down over the longitudinal girders so as to reduce the camber in the track, as directed by the Engineer. 17. All the floor timbers shall have a full and even bear- ing upon the stringers; no open joints or shims will be allowed. 18. On curves the outer rail must be elevated, as may be directed by the Engineer. (§ 5.) Proposals, ig. In Comparing different proposals, the relative cost to the Railroad Company of the required masonry or changes in existing work will be taken into consideration. 20. Contractors in submitting proposals shall furnish com- plete strain sheets, general plans of the proposed structures, and such detail drawings as will clearly show the dimen- sions of all the parts, modes of construction and the sec- tional areas; and state kind of material to be used (§§ 138, 144). 21. Upon the acceptance of the proposal and the execu- tion of contract, all working drawings required by the En- gineer must be furnished free of cost. Approval of 22. No work shall be commenced or materials ordered Flans. until the working drawings are approved by the Engineer in writing ; if such working drawings are detained more than one week for examination, the Contractor will be allowed an equivalent extension of time. LOADS. 23. All the structures shall be proportioned to carry the following loads : 1st. The weight of metal in the structure and floor. Dead Load. 2d. The Weight of rails, fastenings, ties, guards, footwalk and ballast when used. The rails and fastenings being assumed at lOO pounds per foot of track ; timber at 4^ pounds per foot B. M. ; and ballast at no pounds per cubic foot. Minimum will be assumed at 400 pounds per foot of track. These two items, taken together, shall constitute the " dead load." .^1 it © . lis 5i 90 » '" a 5» © . « . ©3 H Q •« <^ (D or '^ <^ 0) PS"" 5S where H^ ratio of depth of web to its thickness; but no web-plates shall be less than three-eighths of an inch in thickness. stiffeners. 48. At any point, the combined stiffeners, fillers and in- closed web, acting together as one column, must be capable of carrying the maximum vertical shear without exceed- ing the allowed unit strain: ' / P = 10,000 — 45 — The stiffeners must connect to the webs by enough rivets to transfer the maximum shear to or from the webs. Rolled Beams. 49. RoUcd beams shall be proportioned (§§31, 45) by their moments of inertia. Counters. 50. Thc areas of counters shall be determined by taking the difference in areas due to the live and dead load strains considered separately (§ 31) ; the counters in any one panel must have a combined sectional area of at least three square inches, or else must be capable of carrying all the counter live load in that panel. (§ 92.) 51. Counters shall be provided and proportioned so that either a future increase of 25 per cent, in the specified live load, or the maximum loading E 50, shall not in anj' case increase the allowed unit strain more than 25 per cent. DETAILS OF CONSTRUCTION. Details. 52. All the connections and details of the several parts of the structures shall be of such strength that, upon testing, rupture will occur in the body of the members rather than in any of their details or connections. 53. Preference will be had for such details as shall be most accessible for inspection, cleaning and painting; no closed sections will be allowed. 13 54- The pitch of rivets in all classes of work shall never Riveting. exceed 6 inches, or sixteen times the thinnest outside plate, nor be less than three diameters of the rivet. (§§ 8i, 96.) 55. The rivets used shall generally be f inch diameter for main members of the trusses and floor, and not less than f for lateral or other bracing. 56. The distance between the edge of any piece and the centre of a rivet-hole must never be less than i| inches, except for bars less than 2^ inches wide; when practicable it shall be at least two diameters of the rivet. 57. For punching, the diameter of the die shall in no case exceed the diameter of the punch by more than ■j\ of an inch, and all holes must be clean cuts without torn or ragged edges. 58. All rivet holes must be so accurately spaced and punched that when the several parts forming one member are assembled together, a rivet yij- inch less in diameter than the hole can generally be entered, hot, into any hole, with- out reaming or straining the metal by " drifts "; occasional variations must be corrected by reaming. 59. The rivets when driven must completely fill the holes. The rivet-heads must be round and of a uniform size for the same sized rivets throughout the work. They must be full and neatly made, and be concentric to the rivet-hole, and thoroughly pinch the connected pieces together. 60. Wherever possible, all rivets must be machine driven. The machines must be capable of retaining the applied pressure after the upsetting is completed. No hand-driven rivets exceeding ^ inch diameter will be allowed. 61. Field riveting must be reduced to a minimum or entirely avoided, where possible. 62. All holes for field rivets, except those in connections of the lateral and sway systems, shall be accurately drilled or reamed to an iron template or be reamed true while the parts are temporarily connected together. 63. The effective diameter of a driven rivet will be as- Net Sections. sumed the same as its diameter before driving. In deduct- ing the rivet-holes to obtain net sections in tension mem- 14 bers, the diameter of the rivet-holes will be assumed as •^ inch larger than the undriven rivets. 64. The rupture of a riveted tension member is to be con- sidered as equally probable, either through a transverse line of rivet-holes or through a zig-zag line of rivet-holes, where the net section does not exceed by 30 per cent, the net section along the transverse line. The number of rivet- holes to be deducted for net section will be determined by this condition. Bolts. 65. When members are connected by bolts the holes must be reamed parallel and the bolts turned to a driving fit. All bolts must be of neat lengths, and shall have a washer under the heads and nuts where in contact with wood. Bolts must not be used in place of rivets, except by special permission. 66. All nuts must be of hexagonal shape. (§93-) Splices. 67. All joints in riveted tension members must be fully and symmetrically spliced. 68. Riveted tension members shall have an effective sec- tion through the pin-holes one-third in excess of the net section of the member, and back of the pin at least 60 per cent, of the net section through the pin-hole (§ 41). Abuttingjoinis. 69. In coutinuous compression members, as chords and trestle posts, the abutting joints with planed faces must be placed as close to the panel points as is practicable, and the joints must be spliced on all sides with at least two rows of closely pitched rivets on each side of the joint. Joints in long posts must be fully spliced. 70. In compression members, abutting joints with un- tooled faces must be fully spliced, as no reliance will be placed on such abutting joints. The abutting ends must, however, be dressed straight and true, so there will be no open joints. webspiices. 71. The webs of plate girders must be spliced at all joints by a plate on each side of the web. stiffeners. 'J2. All web-plates must have stifTeners over bearing points and at points of local concentrated loadings ; such stiffeners must be fitted at their ends to the flange angles, at the bearing points. (§§ 47, 48.) 15 73- All other angles, filling and splice plates on the webs of girders and riveted members must fit at theirs ends to the flange angles, sufficiently close to be sealed, when painted, against admission of water. 74. Web-plates of all girders must be arranged so as not Web piateJ. to project beyond the faces of the flange angles, nor on the top be more than ■j\ inch below the face of these angles, at any point. (§§75>i58.) 75. Wherever there is a tendency for water to collect, the spaces must be filled with a suitable waterproof material. 76. In girders with flange plates, at least one-half of the riangePiaies flange section shall be angles or else the largest sized angles must be used. Flange plates must extend beyond their theoretical length, two rows of rivets at each end. 7y. The flange plates of all girders must be limited in width so as not to extend beyond the outer lines of rivets connecting them with the angles, more than five inches or more than eight times the thickness of the first plate. Where two or more plates are used on the flanges, they shall either be of equal thickness or shall decrease in thickness outward from the angles. 78. In lattice girders and trusses the web members must Lattice Girders. be double and connect symmetrically to the webs of the chords. The use of plates or flats, alone, for tension mem- bers must be avoided, where it is possible; in lattice trusses, the counters, suspenders and two panels of the lower chord, at each end, must be latticed ; all other ten- sion members must be connected by batten plates or latticed. (§97-) 70. The compression flanges of beams and girders shall be compression stayed against transverse cripplmg when their length is more than sixteen times their width, 80. The unsupported width (distance between rivets) of widthofpiates. plates subject to compression shall not exceed thirty times their thickness ; except cover plates of top chords and end posts, which will preferably be limited to forty times their thickness ; where a greater relative width is used in chords and end posts, h»wever, only forty times the thickness shall be considered as effective section. 16 8i. Where the floor timbers are supported at their ends on the flange of one angle, such angle must have two rows of rivets in its vertical leg, spaced not over 3 inches apart. Metai""^"^ 82. For main members and their connections no material shall be used of a less thickness than | of an inch ; and for laterals and their connections, no material less than ^ of an inch in thickness ; except for lining or filling vacant spaces. A^tes'and*^ 83. Connection angles for stringers or floor beams shall Channels, have no leg less than 3^ inches or be of less thickness than I inch. (§ 102.) No angle less than 3x2^ inches shall be used for bracing. The width of channels used for bracing shall not be less than 6 inches for single or 8 inches for double track bridges. Eye-Bars. 84. The hcads of eye-bars shall be so proportioned and made that the bars will preferably break in the body of the original bar rather than at any part of the head or neck. The form of the head and the mode of manufacture shall be subject (to the approval of the Engineer of the Railroad Company. (Art. 141.) 85. The bars must be free from flaws and of full thick- ness in the necks. They shall be perfectly straight before boring. The holes shall be in the centre of the head, and on the centre line of the bar. 86. The bars must be bored to lengths not varying from the calculated lengths more than -^ of an inch for each 25 feet of total length. 87. Bars which are to be placed side by side in the struc- ture shall be bored at the same temperature and of such equal length that upon being piled on each other the pins shall pass through the holes at both ends without driving. 88. The lower chord shall be packed as narrow as possi- ble. Pins. 89. The pins shall be turned straight and smooth ; chord pins shall fit the pin-holes within j\ of an inch, for pins less than 4i inches diameter ; for pins of a larger diameter the clearance may be ^*j inch. 90. The diameter of the pin shall not be less than eight- n tenths the width of the largest eye-bar attached to it. The several members attaching to the pin shall be so packed as to produce the least bending moment upon the pin, and all vacant spaces must be filled with wrought filling rings. 91. All bars with screw ends shall be upset at the ends, upset Ends, so that the diameter at the bottom of the threads shall be yV inch larger than any part of the body of the bar. 92. Where closed sleeve nuts are used on adjustable ^^J^^'J^^.^'^ members the effective length of thread shall be legibly stamped at the screw ends of each bar. Adjustable counters to be avoided where practicable. 93. Screw threads must be of the United States standard, except at the ends of the pins, and except for rods over If in. diameter, where they shall be six threads to the inch. 94. In special cases, where floor beam hangers may be Hangers. permitted, they must be rigidly attached to the trusses and be so arranged as to stay the floor beams firmly against rotation or end motion. (§ 10.) / 95. Compression members shall be of steel, and of ap- compression dr /-.T ^ \ Members. forms. (§ 35.) 96. The pitch of rivets at the ends of compression mem- bers shall not exceed four diameters of the rivets for a length equal to twice the width of the member. 97. The open sides of all compression members shall be Latticing. stayed by batten plates at the ends and diagonal lattice- work at intermediate points. The batten plates must be placed as near the ends as practicable, and shall have a length not less than the greatest width of the member or i^ times its least width. The size and spacing of the lattice bars shall be duly proportioned to the size of the member. They must not be less in width than 2 inches for members 9 inches or less in width, nor 2| inches for members 12 to 9 inches in width, nor 2^ inches for members 15 to 12 inches in width. Single lattice bars shall have a thickness not less than -^-^ or double lattice bars connected by a rivet at the intersection not less than ^V of the distance between the rivets connecting them to the members. They shall be in- 18 clined at an angle not less than 60° to the axis of the mem- ber for single latticing, nor less than 45^^ for double latticing with riveted intersections. The pitch of the latticing must not exceed the least width of the member plus nine inches. 98. Where necessary, pin-holes shall be reinforced by plates, some of which must be of the full width of the member, so the allowed pressure on the pins shall not be exceeded, and so the strains shall be properly distributed over the full cross-section of the members. (§ 41.) These reinforcing plates must contain enough rivets to transfer their proportion of the bearing pressure, and at least on^_ plate on each side shall extend not less than six inches beyond the edge of the batten plates. (§ 97.) 99. Where the ends of compression members are forked to connect to the pins, the aggregate compressive strength of these forked ends must equal the compressive strength of the body of the members. 100. In compression chord sections and end posts, the material must be mostly concentrated at the sides, in the angles and vertical webs. Not more than one plate, and this not exceeding ^ inch in thickness, shall be used as a cover plate, except when necessary to resist bending strains or to comply with § 80. (§ 42.) loi. The ends of all square-ended members shall be planed smooth, and exactly square to the centre line of strain. Floor Beams I02. The cnds of all floor beams and stringers shall be and Stringers. - , , , i i a n faced true and square, and to correct lengths. Allowance must be made in the thickness of the end angles to provide for such facing without reducing the required effective strength of such end angles. (§ 83.) 103. All members must be free from twists or bends. Por- tions exposed to view shall be neatly finished. Pin-Hoies. 104. Piu-holes shall be bored exactly perpendicular to a vertical plane passing through the centre line of each mem- ber, when placed in a position similar to that it is to occupy in the finished structure. 105. The several pieces forming one built member must fit closely together, and when riveted shall be free from twists, bends or open joints. 19 io6. All through bridges shall have latticed portals, of 5^|"^™["^ approved design, at each end of the span, connected rigidly Braang. to the end posts and top chords. They shall be as deep as the specified head-room will allow, and provision shall be made in the end posts for the bending strains from lateral forces. (§§4. ii, 24.) 107. When the height of the trusses exceeds 25 feet, an approved system of overhead diagonal bracings shall be attached to each post and to the top lateral struts. 108. Pony riveted trusses and girders shall be stayed by knee braces or gusset plates at the ends and at intermediate points. 109. All deck girders shall have transverse braces at the ends. All deck bridges shall have transverse bracing at each panel point, of sufficient strength to carry half the maximum strain increment due to lateral and centrifugal forces. This bracing shall be proportioned in double-track bridges to resist the unequal loading of the trusses, with one track loaded. no. In double-track deck bridges, where three trusses are used, all three trusses will be made of equal strength ; the unequal loading being distributed through the trans- verse diagonal bracing as a live load. (For the purpose of reducing the unequal deflection under single-track load- ings.) 111. At all points where floor beams, portals or other Diaphragms, bracing connect with the posts or chords, proper diaphragms must be inserted to distribute the loads and forces over the full section of these posts or chords. 1 12. All members of the web, lateral, longitudinal or sway systems must be securely riveted at their intersections to prevent sagging and rattling. 113. All bed-plates must be of such dimensions that the Bed-piates. greatest pressure upon the pedestal stone shall not exceed 250 pounds per square inch. Their upper bearing surfaces should, preferably, be at least six inches above the masonry. 114. AH bridges over 80 feet span shall have hinged Friction Rollers, bolsters at both ends, and at one end nests of turned fric- 20 tion rollers or rockers running between planed surfaces. These rollers shall not be less than 4J inches diameter for spans 100 feet or less, and for greater spans this minimum diameter shall be increased in proportion of i inch for each 100 feet additional. The rollers shall be so proportioned that the pressure per lineal inch of roller shall not exceed the product of the diameter in inches by 300 pounds (30od.). The rollers must be of machinery steel and the bearing plates of medium steel. The rollers and bearings must be so arranged that they can be readily drained and cleaned. 115. Bridges less than 80 feet span shall be secured at one end to the masonry, and the other end shall be free to move longitudinally upon smooth surfaces. 1 16. Where two spans rest upon the same masonry, a con- tinuous plate, not less than | inch thick, shall extend under the two adjacent bearings, or the two bearings must be rigidly tied together. Pedestals and 1 1 7. Pedcstals shall be made of riveted plates and angles. All bearing surfaces of the base plates and vertical webs must be planed. The vertical webs must be secured to the base by angles having two rows of rivets in the vertical legs. No base plate or web connecting angle shall be less in thickness than | inch. The vertical webs shall be of sufficient height and must contain material and rivets enough to practically distribute the loads over the bearings or rollers. Where the size of the pedestal permits, the vertical webs must be rigidly connected transversely. 118. All the bed-plates and bearings under fixed and movable ends must be fox-bolted to the masonry ; for trusses, these bolts must not be less than i^ inches diameter; for plate and other girders, not less than | inch diameter ; and must be inserted at least six diameters into the masonry. The contractor must furnish all bolts, drill all holes and set bolts to place with sulphur or Portland cement. 119. While the expansion ends of all trusses must be free 21 to move longitudinally under changes of temperature, they shall be anchored against lifting or moving side- ways. 120. All bridges shall be cambered by giving the panels camber. of the top chord an excess of length in the proportion of ^ of an inch to every ten feet. 121. The lower struts in trestle towers must be capable Trestle Towers, of resisting the strains due to changes of temperature or of moving the tower pedestals under the effects of expansion or contraction. For high or massive towers, these lower struts will be securely anchored to intermediate masonr}' piers, or the tower pedestals will have suitably placed friction rollers, as may be directed by the Engineer. 122. All joints in the tower columns shall be full}' spliced for all possible tension strains, and to hold the parts firmly in position. (§§ 25, 69.) 123. Tower footings, pedestals and bed-plates must be planed on all sliding surfaces ; and the holes for anchor bolts slotted to allow for the proper amount of movement. (§ 28.) 124. All workmanship shall be first class in every par- workmanship. ticular. 125. All eye-bars must be made of Medium Steel. (§§ 138-142.) 126. Eye-bars, all forgings and any pieces which have Eye-Bars, been partially heated or bent cold must be wholly an- nealed. Crimped stiffeners need not be annealed. 127. No reliance will be placed upon the welding of steel. 128. No sharp or unfilleted angles or corners will be allowed in any piece of metal. 129. The steel (§§ 138-144) may be used in tension with- Reaming, out reaming of punched holes up to| inch in thickness, and may be used in compression without reaming for all thick- nesses of metal which will stand the drifting test. (§ 146.) In all other cases, the steel must have all holes drilled or reamed to a diameter | inch larger than the punched holes. 24 142. Full sized material for eye-bars shall bend cold i8o° to a curve, whose inner radius is equal to the thickness of the material, without fracture on the outside of the bend. 143. Pins over 7 inches in diameter shall be forged. Blooms for pins shall have at least three times the sectional area of the finished pins. (§ 138.) Low Steel. *i44. LowT Stccl shall have an ultimate Strength, On Same sized samples, of 55,000 to 65,000 pounds per square inch, an elastic limit not less than one-half the ultimate strength, and a minimum elongation of 23 per cent, in 8 inches. 145. Before or after heating to a light yellow heat and quenching in cold water, this steel must stand bending 180 degrees, to a curve whose inner radius is equal to the thickness of the sample, without sign of fracture. 146. For both kinds of steel, | inch or less in thickness, rivet holes punched as in ordinary practice (§§ 55, 56, 57), Drifting, must Stand drifting to a diameter one-third greater than that of the original holes, without cracking either in the periphery of the holes or on the external edges of the piece, whether they be sheared or rolled. Rivet Steel. 147. Rivet Stccl shall have an ultimate strength of 48,000 to 58,000 pounds per square inch, an elastic limit not less than one-half the ultimate strength and an elongation of 26 per cent. 148. The steel for rivets must, under the above bending test (145), stand closing solidly together without sign oi fracture. When nicked and bent around a bar of its own diameter it shall break gradually and give a fine, uniform, silky fracture. Variation in 149. A Variation of cross-section or weight in the finished members of 2^ per cent, from the specified size may be cause for rejection. Steel Castings. Steel Castings. 1 50. Stccl Castings will be used for drawbridge wheels, track segments and gearing. (Art. i.) * Use permitted, but not recommended. 25 They must be true to form and dimensions, of a work- manlike finish and free from injurious blowholes and defects. All castings must be annealed. When tested in specimens of uniform sectional area of at least ^ square inch for a distance of 2 inches, they must show an ultimate strength of not less than 67,000 pounds per square inch, an elastic limit of one-half the ultimate, and an elongation in 2 inches of not less than 10 per cent. The metal must be uniform m character, free from hard or soft spots, and be capable of being properly tool finished. Cast Iron. 151. Except where cast steel or chilled iron is required, cast iron. all castings must be of tough, gray iron, free from cold shuts or injurious blowholes, true to form and thickness, and of a workmanlike finish. Sample pieces, i inch square, cast from the same heat of metal in sand moulds, shall be capable of sustaining, on a clear span of 12 inches, a central load of 2,400 pounds, when tested in the rough bar. A blow from a hammer shall produce an indentation on a rectangu- lar edge of the casting without flaking the metal. Timber. 152. The timber shall be strictly first-class Timber. southern yellow pine or white oak bridge timber, sawed true, and out of wind, full size, free from wind shakes, large or loose knots, decayed or sap wood, worm holes, or other defects impairing its strength or durability. It will be subject to the inspection and acceptance of the Engineer. INSPECTION. 153. All facilities for inspection of the materials and inspection. workmanship shall be furnished by the contractor. He shall furnish without charge such specimens (prepared) of the several kinds of steel to be used, as may be required to determine their character. 28 Weight of any single piece must not exceed pounds. Pins, roller-nests, bolts, rivets and all small pieces must be packed in strong, iron-bound boxes, with the detailed contents of each box legibly marked on the outside. Boxes to be consecutively lettered or numbered. The screw-ends of all bars to be securely protected by canvass wrapped and wired about the same. Every piece must not only be legibly marked by paint, but also by letters stamped on the metal, showing its loca- tion in the structure. All necessary rivets for the field connections, with an extra allowance of 25 per cent, for each kind, shall be sent with each shipment. The customary pilot nuts (§ 132) for all pins shall be sent with the pins. Proposals for building and erecting complete, ready for the , a bridge over. near on the Division,. Railroad, in accordance with the attached specifications and accompanying profile, will be received up to The live load to be adopted for this bridge will be Class E paragraph 23. CHANGES AND ADDITIONS HADE IN THIS EDITION. §§ 5, lo, 14, 20, 23, 24, 26, 29, 31, 32, 33, 35, 36, 38, 39, 40, 41,48,51, 55,68, 81,83, 90.93. 94. 108, 109, III, 113, 114, 118, 123, 129, 133, 134, 138, 140, 142, 144, 146, 147, 148, 156, 157, Table III. APPENDIX. 32 TABLE I. Maxiitom Moments M, End Sheabs 8, and Plooe-Beam Keacitons R, PBB Track, fok Loading E 40, fob Gibdbb Bbidgbs. Max. floor reac. B. Lbs. Equivalent Uniform Load. "r Max. mom. M. Max. end shear S. Ft. Ft.-Ibs. Lbs. M. S. B. Lbs. Lbs. Lbs. 10 118 500 60 000 80 000 9 000 13 OOO 8 OOO 11 181 400 65 600 87 800 8 690 11 910 7 940 18 160 000 70 000 98 800 8 890 11 670 7 770 18 190 000 78 800 98 600 9 000 11 360 7580 14 220 000 77 200 104 300 8 980 11 030 7 450 15 260 000 80 000 109 300 8 890 10 670 7 290 16 280 000 85 000 118 700 8 750 10 630 7 110 17 310 000 89 500 117 600 8 580 10 530 6 920 18 340 000 93 400 121 300 8400 10S80 6 740 19 373 200 96 800 125 800 8 370 10 190 6 620 20 412 500 100 000 131 100 8 260 10 000 660 21 453 000 102 800 136 000 8200 9 790 6 480 23 491 40O 105 600 140 300 8 120 9 590 6380 23 580 800 107 900 144 300 8 030 9 380 6 270 24 570 400 110 800 148 000 7 980 9 230 6 170 25 610 000 113 600 151 800 7 810 9 090 6 050 26 649 600 lie 100 155 400 7 690 8 930 5 970 27 689 200 118 500 160 100 7 560 8 780 5 930 28 731 000 120 800 164 600 7 460 8 630 5 875 29 775 800 123 100 168 700 7 370 8 490 6 820 30 821 000 126 100 178 500 7 300 8 410 6 750 31 865 700 138 800 1T6 900 7 219 8 310 6 710 32 910 800 131 500 189 000 7 120 8 280 5 690 38 955 600 1 000 700 133 900 186 100 186 700 191 100 7 020 6 920 8 110 8 010 6 660 34 5 630 35 1 046 000 188 400 196 200 6 840 7 910 6 570 36 1 097 000 1 148 600 1 200 000 1 253 500 1 311 000 1 487 000 1 543 000 1 659 000 1 776 000 1 903 000 2 030 000 2 162 000 3 304 000 2 446 000 2 699 000 2 768 OOO 2 911 000 3 079 000 3 247 000 3 415 000 3 684 000 3 768 000 3 942 000 4 129 000 4 321 000 4 618 000 4 713 000 4 919 000 5 188 000 5 841 000 5 652 000 5 771 000 5 988 000 6 213 000 6 440 000 7 075 000 7 774 000 8 490 000 9 228 000 9 993 000 141 100 143 800 146 300 148 600 150 800 156 200 161 ion 166 600 169 600 174 200 178 500 182 400 186 000 190 800 195 300 200 300 205 200 210 000 215 600 821 000 336 700 282 600 288 100 243 400 848 400 253 800 259 000 364 300 289 400 274 500 879 600 884 700 ■ 889 600 895 000 800 000 312 800 824 000 836 800 847 400 368 800 6 770 6 710 650 6 590 6 560 6 480 6 870 6 280 6 170 6 090 6 010 5 930 6 880 6 820 5 780 5 780 5 690 6 660 6 610 5 580 5 540 5 490 . 6 460 5 430 5 400 5 870 5 840 6 320 5 300 5 880 5 860 5 280 B200 6 180 5 150 5 160 5 140 5 140 5 130 6 130 7 840 7 770 7 700 7 620 7 640 7 460 7 320 7 200 7 070 6 970 6 870 6 760 6 640 6 580 6 510 6 460 6 410 6 360 6 840 6 310 6 800 6 290 6 270 6 240 6 210 6 190 6 190 6 160 6 180 6 100 6 080 6 060 6 030 6 080 6 000 6 960 6 890 5 840 5 790 5 740 37 38 39 40 42 44 46 Trestles 30 and 60 fPet spans, 238,800 48 50 53 54 56 58 40 and 60 feet spans, 262,900 60 62 64 66 68 70 72 74 76 78 80 88 84 86 88 90 98 94 96 98 100 105 110 115 120 125 Note— For all other classes, the above values to be proportional to the classes. TABLE II. Maximum Moments M aud End Shears .S^ pek Tback, pkoducbd by SPEciAii Loads on Two Axles, g 23. 100,000 Lbs. fob An. Classes up TO E 40. 10 130,000 Lbs. pok All Classes over E40. a Max. mom., M. Ft.-lbs. Max. shears, S. Lbs. Equlv. unif. load. Max. mom., M. Ft.-Lbs. Max. shear, S. Lbs. Equiv. unif. load. m M. Lbs. S. Lbs. M. Lbs. S. Lbs. 5 10..- 125 000 70 000 10 000 14 000 160 000 84 000 12 OOO 16 800 11..- 145 500 72 700 9 620 13 220 174 600 87 250 11 550 15 850 12... 168 750 192 300 75 000 76 900 78 600 9 870 9100 12 500 11830 11220 E40 202 500 90 000 92 800 11 250 15 000 14 200 13... 280 760 259 300 238 000 11 000 10 600 10 250 E50 14... 216 1(J0 240 000 8820 8 540 94 300 96 000 13 500 12 800 15... 80 000 10 670 16... 264 000 288 250 81 250 82 300 8250 7 990 10160 9 680 816 800 97 500 9 900 12 200 E46 17... 345 900 98 800 9 580 11 600 18... 312 500 88 800 7 700 9 263 375 000 100 OOO 9 260 11 100 19... 336 850 361 200 m 200 7 460 7 220 8 860 E35 404 200 488 500 101 100 8 960 8 660 10 600 E41 20... 85 000 85 700 86 350 8B950 8 500 8 160 7 850 7 560 102 000 102 900 10 300 9 800 21... 885 700 410 200 484 800 7 00D 6 780 6 570 462 900 492 800 8 400 8 140 22.. 108 600 9 400 23... 24... 459 400 87 500 6 380 7 300 25... 484 000 88 000 6 200 7 040 86... 508 650 88 600 6 020 6 810 27... 583 800 558 000 88 900 5 850 5 700 6 585 E30 28... 89 300 6 380 29, 582 900 5 540 u • »• • B . ffi. ■ p -ft Eo_,°' p.- W Mi Si W.Wfp.^ttwl : ?=»: ■•"" C3D- hrf'-l ■ tdpr: SSSSSS CTTOl CtOO 51 t.apsipg ts tocotctototoiototot-ii-L WOSOtiCOtOCOl-'OtOsD OOWOOOTOOtOOOOO gQOOOO=?OOQO 0C30OO00000 OQQOOOOOOOO ooSoooooooo cj» -5 000-31- 0Ml-ilglOM--l^l-H- OWODOlOWtOOOOO SOOQOQOOOOO ^0000000000 OM*i.3J»-*-"C»0500SOO 0000W0t30000 ^ ^^ )_i M- M- M. CO o OS 00 o -;; O-IOWCJJO iSSS Sooo COOSOCOCSOI 03 CO O CO o o 000000 01 ll^ lllk C7I »C>- O) ' GOQOCOCOtSO 80CS000 00000 00 M- -:| 01 -Q OS OM*. OOL OS 000000 OOQOODtOOOO-500-Q-5 -O OD CO -3 00 -nI 0> "-l — J OS -^ Oi CCrt^Q0«CM-3 O^OD^UTUi o o 0000 ■S-E 013 o £5. ft p ft ^ B o 2 pil-hTO S? B- a o pg ft " O P 3.S1-3 S" B — Sift ft ^)-h tp o o B5g ft !?_j ^ os-^oscioscioscsoswcn -5C0-QCSO-^O<£)-'W-^ 0lCDlC>.:O6C>Jl.OtD&5t0O oooocnwc3ioo-5^ OS OS OS en en oi Mh^OSOO-Q-^ QOO«3h-ig E. 88 to E. 40 for short spans. So eg rf.s| S,B '^O- fed Q a I^ H CD t> CC W y t^ Q w w W !2! b>. 5 ^ B o w Q H a H 35 RELATIVE COST OF BRIDGES Built Under These Specifications FOR THE DIFFERENT CLASSES OF LOADINGS. The increased cost and weight of metal bridges of all kinds, built under the requirements of these specifications, will be approximately as follows : For bridges of Class E 35 over those of Class E 30 will be E 40 " " E 35 E 45 " " E 40 E 50 " " E 45 10 per cent. Recommendation. Table III gives a selection of heavy passenger and freight engines typical of those in use on the principal railroads of the United States at the beginning of the Twentieth Cen- turJ^ As far as the effects upon the bridges are concerned, these engines are represented by the typical train loadings of these specifications, E 38 to E 50. The heavier of these engines are close to the possible maxi- mum, considering the limitations of the permissible cross section of existing railroads, fixed wheel base and the mechanical details of design and proportions. There are now in general use cars of a nominal capacity of 100,000 pounds which have on four axles a total load of 146,000 pounds (10 per cent, increase over nominal capacity) on a wheel base, for two adjacent cars, of 17 ft. 2 ins. These 36 cars on all ordinary bridges produce strains equivalent to those of E ^^. There are special cars which have, when fully loaded, 50,000 pounds on each axle, but such cars would never be put together in series. It is recommended that train loading E 40 be the minimum adopted by any railroad in North America carrying general traffic. Train load £50, under the requirements of these specifications, will, in the opinion of the author, be sufficient to provide for any possible future loading. Many important systems have already adopted it as their standard loading. THEODORE COOPER.