RAILROAD BRIDGES 31 



rigidily connected to the end posts and the top chords. They 

 shall be as deep as the clearance will permit. 



Intermediate transverse frames shall be used at each panel 

 of through spans having vertical truss members where the 

 clearance will permit. 



Lateral bracing shall be far enough below the flange to clear 

 the ties. 



The minimum-sized angle to be used in lateral bracing shall 

 be 3J"X3"Xf". Not less than three rivets through the end of 

 the angles shall be used at the connection. 



132. Steel Trestles. The struts at the foot of trestle towers 

 shall be strong enough to slide the movable shoes when the track 

 is unloaded. (Par. 84.) 



133. All Structures. Structures shall be so designed that 

 all parts will be accessible for inspection, cleaning, and painting. 



Pockets or depressions which would hold water shall have 

 drain holes, or be filled with waterproof material. 



DETAILS OF DESIGN 



134. Minimum Size of Material. The minimum thickness 

 of metal, except for fillers, shall be f in. 



Flanges of girders or built members without cover plate 

 shall have a minimum thickness of one-twelfth (-%) of the width 

 of the outstanding leg. (Par. 131.) 



135. Details of Joints. Main members of trusses shall be 

 so arranged around the joints that their neutral axes will be as 

 nearly as practicable in the center of the section and the neutral 

 axes of intersecting main members shall meet in a common point. 



Abutting joints in compression members when faced for bear- 

 ing shall be spliced on four sides sufficiently to hold the connect- 

 ing members accurately in place. 



All other joints in riveted work, whether in tension or in com- 

 pression, shall be fully spliced. 



Where splice plates are not in direct contact with the parts 

 which they connect rivets shall be used on each side of the joint 

 in excess of the number theoretically required to the extent of 

 one-third (-J-) of the number for each intervening plate. 



136. Details of Connections. The strength of connections 

 shall be sufficient to develop the full strength of the member, 



