INSTRUCTIONS TO DRAFTSMEN, C. M. & ST. P. RY. 223 



8. Clearance for Riveting. When flanges of angles and channels of built members are turned 



in, 5i in. opi-nin^ U-i wt-.-n c.l-r-, ot aiu.K -, or ili.uin.l-, is required torivet the tic platcaand lacing. 



LATERAL AND SWAY BRACING. i. Minimum Sizes. The minimum size of ai 

 to In- and in br.u-inus shall be 3i" X 3" X J". Not less than three rivets shall be used in the 

 connection. 



2. Effective Section. Where single angles are used for bracing members without lug angler 

 connecting the outstanding leg to the gusset plates, not more than 80 per cent of the net section, if 

 in U-IIM .HI, >h.ill be considered as effective. 



\Vlu n- single angles, used for bracing members, have lug angles connecting their outstanding 

 legs to the gusset plates, and where the center of the group of connecting rivets in the gusset 

 plates fall close to the gravity line of the angle, in plan, 90 per cent of the net section may be 

 considered effective. 



3. Double Diagonal Systems. In double diagonal systems the shear due to wind force shall 

 be considered as carried wholly by one diagonal in tension, but the maximum value of IJr 120, 

 specified for bracing members, shall not be exceeded. In assuming "r" the connection of di- 

 agonals at their intersection may be considered as offering support against deflection in the plane 

 of the system, but not against deflection perpendicular thereto. 



4. Bending at Connections. Connections between bracing members and chords shall be 

 designed to avoid as far as possible any bending stress in main truss members. 



5. Allowance for Draw. For diagonal bracing of one or two angles the following draw 

 should be allowed: 



For lengths up to 10 ft. No Allowance, 



from 10 to 21 ft. Allow & in. 



from 21 to 35 ft. Allow | in. 



over 35 ft. Allow ^ m - 



The use of thirty-seconds of an inch should be avoided but the above allowances should not be 

 varied by more than ^j in. 



LATERAL BRACING. i. Lateral Bracing. Lateral bracing shall be in general as follows: 



(1) Deck girders and top flanges of stringers 15 ft. long and over; single diagonal system with 

 transverse struts, composed of single angles. Slope of diagonals 45 to 60 with axis of bridge. 



(2) Through girders: Do'uble diagonal system of same panel length as floor system, com- 

 posed of single angles; floorbeams to act as the transverse struts of the system. 



(3) Trusses, loaded chord: Double diagonal systems of same panel length as floor systems, 

 composed of single angles, or double angles back to back; floorbeams to act as the transverse 

 struts of the system. 



(4) Trusses, unloaded chord: Double diagonal systems of same panel length as floor system 

 with transverse struts at panel points; all composed of two or four angles laced to form a channel 

 or I-section, of depth equal to depth of chords. 



2. Traction Stresses. The lateral system in the plane of the loaded chord of truss spans and 

 of through girder spans shall be effectively riveted to the stringers at intersections, and the diagonal 

 shull be designed to transmit the traction for one panel length of track to the panel point; one 

 diagonal for each stringer considered acting in tension. 



3. Clipping Angles for Clearance. The vertical leg of laterals should be clipped -at the end 

 when there is a possibility that the square corner would interfere in any way with putting in the 

 laterals or riveting up. This is to be particularly looked out for at floorbeam connections of 

 through girder spans and in top laterals of Type A4 girder spans. 



4. Squaring of Holes in Connections. Where laterals are riveted to stringers the holes 

 should be squared with the stringers, if possible. At the intersection of diagonals, the holes in 

 splices with two lines c' 



5. Tie Plates and 

 bars, they should bedet 



6. Lateral Plates 3 and C4 Spans. The lateral plates of Type C3 and Type C4 girder 

 spans (flanges two angles and cover plates) should not be shop riveted to the girders, as it is 

 impossible to put in floorbeam connection angles when this is done. 



TRANSVERSE BRACING. I. Transverse bracing shall be used as follows: 



(1) At intervals of not more than 15 ft. on deck girder spans. Intermediate frames shall be 

 of minimum material. End frames shall be designed to carry to the abutment the total lateral 

 forces acting on the top flange. End frames of skew deck gilders shall be placed at the end 

 of the short girder, and at right angles to same. Top and bottom lateral diagonal braces shall 

 be used to stay the end of the long girder. 



(2) As spacers for stringers resting on masonry where end floorbeams cannot be used. These 

 frames shall be riveted to girders or truss shoes where practicable. 



(3) As spacers for stringers at all expansion points. 



(4) At end panel of through truss spans, having vertical truss members. These frames 

 shall be as deep as clearance will permit. 



