60 STEEL ROOF TRUSSES AND MILL BUILDINGS. CHAP. I. 



61. Windows. Windows shall be provided in the exterior walls equal to not less than 10 per 

 cent of the entire exterior surface in mill buildings, and of not less than 25 per cent in machine 

 shops, factories, washeries, concentrators, breakers and similar buildings. 



Window glass up to 12. in. X 14 in. may be single strength, over 12 in. X 14 in. the glass 

 shall be double strength. Window glass shall be A grade except in smelters, foundries, forge 

 shops and similar structures, where it may be B grade. The sash and frames shall be constructed 

 of white pine. Where buildings are exposed to fire hazard the windows shall have wire glass set 

 in metal sash and frames. 



62. Skylights. At least half of the lighting shall preferably be by means of skylights, or 

 sash in the sides of ventilators. 



Skylights shall be glazed with wire glass, or wjre netting shall be stretched beneath the 

 skylights to prevent the broken glass from falling into the building. Where there is danger of 

 the skylight glass being broken by objects falling on it, a wire netting guard shall be provided 

 on the outside. 



Skylight glass shall be carefully set, special care being used to prevent leakage. Leakage 

 and condensation on the inner surface of the glass shall be carried to the down-spouts, or outside 

 the building by condensation gutters. 



63. Windows in sides of buildings shall be made with counterbalanced sash, and in venti- 

 lators shall be made with sliding or swing sash. All swinging windows shall be provided with a 

 satisfactory operating device. 



64. Doors. Doors are to be furnished as specified and are to be provided with hinges, tracks, 

 locks and bolts. Single doors up to 4 ft. and double doors up to 8 ft. shall preferably be swung 

 on hinges; large doors, double and single, shall be arranged to slide on overhead tracks, or may be 

 counterbalanced to lift up between vertical guides. 



Steel doors shall be firmly braced and shall be covered with No. 24 corrugated steel with I J 

 in. corrugations. 



The frames of sandwich doors shall be made of two layers of f in. matched white pine, placed 

 diagonally, and firmly nailed with clinch nails. The frame shall be covered on each side with a 

 layer of No. 26 corrugated steel with ij in. corrugations. Locks and all other necessary hard- 

 ware shall be furnished for all windows and doors. 



(Sections 65 to 77 cover specifications for tar and gravel roofing and concrete and wood floors 

 which have already been given.) 



DETAILS OF CONSTRUCTION. 



78. Details. All connections and details shall be of sufficient strength to develop the full 

 strength of the member. 



79. Pitch of Rivets. The pitch of rivets shall not exceed 6 in., or sixteen times the thickness 

 of the thinnest outside plate in the line of stress, nor forty times the thickness of the thinnest 

 outside plate at right angles to the line of stress. The pitch shall never be less than three diameters 

 of rivet. At the ends of compression members the pitch shall not exceed four diameters of the 

 rivet for a length equal to twice the width of the member. 



80. Edge Distance. The minimum distance from the center of any rivet hole to a sheared 

 edge shall be i in. for in. rivets, i j in. for f in. rivets, i| in. for f in. rivets, and I in. for 5 in. 

 rivets, and to a rolled edge i}, i|, i and f in., respectively. The maximum distance from the 

 edge shall be eight (8) times the thickness of the plate. 



81. Maximum Diameter. The diameter of the rivets in angles carrying calculated stresses 

 shall not exceed j of the width of the leg in which they are driven, except that f in. rivets may 

 be used in 2 in. angles. 



82. Diameter of Punch and Die. The diameter of the punch and die shall be as specified 

 in 147. 



83. Net Sections. The effective diameter of a driven rivet will be assumed the same as 

 its diameter before driving. In deducting the rivet holes to obtain net sections in tension members, 

 the diameter of the rivet holes will be assumed as | inch larger than the undriven rivet. 



84. Minimum Sections. No metal of less thickness than ? in. shall be used except for 

 fillers; and no angles less than 2" X 2" X i". The minimum thickness of metal in head frames, 

 rock nouses and coal tipples, coal washers and coal breakers shall be j^ in., except for fillers. 

 No upset rod shall be less than f in. in diameter. Sag rods may be as small as f in. diameter. 



85. Connections. All connections shall be of sufficient strength to develop the full strength 

 of the member. No connections except for lacing bars shall have less than two rivets. All field 

 connections except lacing bars shall have not less than three rivets. 



86. Flange Plates. The flange plates of all girders shall not extend beyond the outer line 

 of rivets connecting them to the angles more than 6 in. nor more than eight times the thickness 

 of the thinnest plate. 



