Page images
PDF
EPUB

Shearing
Rivets and pins..

10,000 10,000 10,000 For hand-driven rivets re

duce 20 per cent. Webs of plate girders..... 9,000

8,000

7,000 I= length in inches. r = least radius of gyration in inches.

21. No compression member shall have a length greater than 45 times its least width, or 102 times its least radius of gyration, except a member of lateral or wind bracing systems, which may have a length of 140 times its least radius of gyration.

22. All members subject to stresses of both tension and compression shall be designed to sustain both stresses with eight-tenths of the smaller added to each.

23. For knee braces, sway braces and wind bracing, increased above stresses for shapes and plates, 30 per cent, but do not increase stresses for rivets.

24. For combined live, dead and wind stresses, increase the preceding unit stresses 30 per cent above live and dead load unit stresses.

25. Where steel work is liable to corrosion, as when exposed in foundry buildings, increase sections to suit conditions as specified by the Railroad Company.

26. Bolts when used in place of rivets shall be allowed only two-thirds of the above unit stresses.

27. All bed plates shall be of such dimensions that the greatest pressure per square inch, due to any or all causes, upon the masonry shall not exceed: Stone masonry, 300 lb.; concrete masonry, 250 lb.; brick work, 150 lb.

28. Where lateral bracing consists of a double system of cancellation the lateral stresses shall be assumed to be equally divided between the two systems.

29. All horizontal or inclined members must be proportioned to sustain the combined stresses due to direct compression or tension and to the weight of the members and their transverse loads, but the combined unit stress from these causes must not exceed the unreduced direct unit stress by more than 10 per cent.

30. All struts must be proportioned to resist the resultant due to an initial stress of 10,000 pounds on all rods attached to them whenever this is in excess of the maximum stress produced from other causes.

31. All “I” beams shall be proportioned by their moment of inertia.

32. No part of the web-plate shall be estimated as flange area in proportioning plate girders.

GENERAL DETAILS 33. In general, strength and simplicity shall be the first consideration in design of any structure and any arrangements of members which introduce uncertainty or indeterminateness of stresses must be avoided

34. Due regard must be paid to the neat and attractive appearance of the finished structure and details of an unsightly character will not be approved.

35. All connections and details shall be of sufficient strength to develop the full strength of the member unless otherwise allowed by the Railroad Company.

36. Roof trusses shall be spaced if possible at such distance apart as to allow of single shapes to be used for purlins. It is desirable to avoid trussed purlins.

36a. Trusses shall preferably be riveted structures. Heavy trusses of long spans which would be unwieldy in erection, or on account of field riveting, or for any other good reasons, may be designed as pin-connected structures.

36b. Main members of trusses shall be designed so that the neutral axes of intersecting members shall, if practicable, meet in a common point.

37. Trusses over 100 feet span on walls shall have expansion rollers.

38. Sway and wind bracing shall be introduced at such points as may be necessary to insure sufficient transverse and longitudinal strength and rigidity.

38a. Roof trusses shall be braced in pairs in the planes of their upper chords.

39. All stresses from sway or wind bracing shall preferably be carried to the foundation direct, but may be accounted for by bending in columns.

40. Wall anchors shall be provided at not less than five-foot intervals with all floor beams, girders, roof purlins, etc., which come near or in contact with the interior walls.

40a. Floor Beams.-May be rolled beams or plate girders; they shall preferably be riveted or bolted to the columns by means of connecting angles. Shelf angles or other supports may be provided for convenience. during construction.

40b. Floor Joist.--Shall generally be rolled beams, and the ends shall be attached to the webs of floor beams and columns with angle connections.

41. Upper chords of trusses or rafters shall have symmetrical crosssection and shall preferably consist of two angles back to back.

42. All other compression members, except sub-struts, shall be composed of sections syinmetrically placed. Sub-struts may consist of a single shape.

43. Purlins shall be attached to the rafters by clips with at least two rivets at each end of each purlin, except at expansion joints where bolts must be used.

44. Laced compression members shall be stayed at the ends by batten plates having a length not less than the depth of the member.

45. Rivets and bolts preferably should not be used in direct tension.

46. No rivet hole shall be closer to the edge of a plate than 174 inches, except in bars less than 24 inches wide.

47. The effective diameter of the driven rivet shall be assumed the same as before driving.

48. In making deductions for rivet holes in tension members the holes shall be assumed one-sixteenth of an inch larger than the undriven rivet.

49. Tension members shall preferably be angles or shapes.

50. Angles in tension shall be connected by both legs or only one leg shall be considered as being effective.

51. Long laterals or sway-rods may be made of rods with sleeve nut adjustment.

52. No upset rod shall be less than five-eighths of an inch diameter. Sag rods may be as small as five-eighths inch.

53. All rods with screw ends must be upset. The area at root of thread in lipset ends shall be greater than the area of the rod by at least 17 per cent.

54. Bed plates shall not be less than one-half inch thick.

55. Each column base or bearing plate shall be provided with two anchor bolts of not less than three-quarters of an inch in diameter, either built into the masonry or extending far enough into it to make it effective.

56. Stiffeners must be used at intervals equal to the depth of girder whenever the ratio of the unsupported depth of the web to its thickness exceeds fifty; also at points of concentrated loads.

57. The compression flange of girders shall be stayed against transverse buckling at distance not exceeding twenty times their width or proper reduction be made in the unit stresses in computing the size of the flanges.

58. Top Aange of built beams shall have the same gross area as hottom flange when of the same cross-section.

59. No material less than one-quarter of an inch thick shall be used except for fillers, and no webs of girders shall be less than five-sixteenths of an inch thick. No angles smaller than 2 in. x 2 in. x 1/4 in. shall be used

60. Where two or more cover plates are used in the flanges of girders they shall be of equal thickness, or shall decrease in thickness outward from the angle; the cover plate shall not extend more than 5 inches, or eight times the thickness of plate, beyond the outer line of rivets. In cover plates more than 14 inches wide four lines of rivets shall be used. Where practicable, the bottom cover plate of the top flange must run the whole length of the girder.

61. Pitch of rivets shall not be more than 6 inches or more than sixteen times the thinnest plate connected, or less than three times the diameter of rivets.

62. Rivet holes of the following portions of the structure, in metal 12 inch thick or over, shall be punched to a diameter 18 of an inch smaller on the die side than the finished diameter of the hole, and shall afterwards be reamed to a diameter one-sixteenth of an inch larger than that of the cold rivet:

(a) Flanges of all plate girders.
(b) Main compression members.
(c) All field connections.

This clause does not apply to roof trusses, which shall be punched work only, unless otherwise specified.

63. The roller end in every truss shall be free to move longitudinally under changes of temperature, but it must be securely anchored against lifting or moving sideways. The fixed end in every case shall be rigidly secured so that no motion can take place in any direction.

64. All members must be straight between points of connection.

WORKMANSHIP

65. All workmanship must be first class in every respect.

66. All abutting surfaces of compression members, except flanges of plate girders, which must be fully spliced, must be planed or turned so as to insure even bearings.

67. In all cases where it is necessary to partially heat a steel member, the whole piece must be subsequently annealed.

68. Built members, when finished, must be true and free from twists, kinks, buckles, or open joints between component parts.

69. Rivet holes must be accurately spaced and exactly opposite each other,

70. Rivets must be of the best quality of rivet steel, must completely fill holes, and must have full heads. Rivets for field work must have full and perfect heads, with underside of head square to shanks, shanks must be of a uniform circular section throughout and cut square at end, and must be free from projections or imperfections which would prevent the head from fitting closely before rivet is driven.

71. Eye-bars shall be die-forged without welds.

72. Columns shall be designed to provide for effective connections of floor beams, girders and brackets.

The column splices shall be designed to resist the bending stresses, and so as to make the columns practically continuous for their whole length. Columns shall be preferably continuous over several stories, and the joints so arranged that the splices on all columns do not occur in the same story.

73. All surfaces inaccessible after assembling must be painted with a good quality of red lead paint before the parts are assembled. After work is finished at the shops, it shall be cleansed of all loose scale and rust, and thoroughly and evenly covered with one coat of red lead paint before shipping. All planed or turned surfaces must be coated with white lead and tallow.

74. Projecting members, liable to be bent or injured in transit, must be blocked with wood before shipment in such a way as to protect them from injury in handling.

75. All material must be thoroughly straightened before being laid off or worked in any way.

76. No sharp unfilleted angle will be allowed anywhere, and wherever plate or shape has been cut into, the fillets as well as the cut must be finished so that no sign of the punched or sheared edge remains.

77. In punched work the diameter of the die shall not be more than one-sixteenth of an inch greater than the diameter of the punch. Riveted work shall be assembled so that the punch sides shall come together.

78. Riveted members must have all parts well pinned up and drawn together before riveting up, so that when finished they will be free from open joints and the component parts will lie close on each other.

79. All rivets must be driven by machine where possible, and where not possible, pneumatic driven rivets will be preferred to hand rivets.

80. Wherever practicable, reaming must be done after all pieces which are to be fastened together by the same rivets have been assembled. If necessary to take the pieces apart for shipping or handling, the respective pieces reamed together must be so marked that they may be reassembled in the final setting up. No interchanging of pieces after reaming will be allowed.

All spliced members shall be put together in the shop, and the field rivet holes reamed to a fit while these members with their splice plates are in place.

81. All stiffeners must have a tight fit between upper and lower flanges of girders.

82. No material shall be rolled or work done before the Railroad Company has been notified to what mill or works, orders have been assigned and arrangements have been made for inspection.

83. Complete copies of mill orders and plans will be furnished to the inspector, and he must be notified in time to be on hand when work is begun on his orders.

84. The Contractor must furnish all facilities for inspecting the workmanship and testing the quality of all material furnished on the order at the mill or shop where the material is manufactured.

85. The Inspector must be given reasonable facilities to check the weights finished members before shipment. Not more than 29/2 per cent excess weight over figured weight will be paid for by the Railroad Company.

86. Wherever bolts are used in place of rivets the holes must be reamed true to size after work is assembled, the bolts must be turned to a driving fit and their threads reduced one-eighth of an inch in diameter under size of finished bolts. A small washer, one-eighth of an inch thick, must be used under nut.

87. In case of local building ordinances conflicting with these specifications in whole or in part, the requirements of such ordinances will take precedence over these specifications

« PreviousContinue »