64 STANDARD SPECIFICATIONS 



284. Guard Rails (Railroad Bridges). The minimum size of 

 the outer guard rails shall be 6" X 8" (laid on flat) and so placed 

 that their inner faces are not less than 3 ft. 3 in., or more than 

 3 ft. 6 in., from center of track. 



The minimum size of the inner guard rails shall be 6"XS" 

 (laid on flat) and so placed that their outer faces are not less 

 than 1 ft. 11 in., or more than 2 ft. from center of track. 



All guard rails shall be continuous over piers and abutments; 

 they shall be spliced with half-and-half joints over a tie, shall be 

 notched 1 in. over every tie and shall be fastened to every third 

 tie and through the splice by a three-quarter (}) in. bolt. The 

 floor system shall be fastened to the supporting girders by a 

 three-quarter (J) in. hook bolt through every third tie. 



All heads ox nuts of bolts on the upper faces of guard rails 

 shall be countersunk into the wood and placed in a cup washer. 



285. Pile Trestles. For heights less than 30 ft. pile trestles 

 may be used, and their spacing, center to center of bents, shall 

 not exceed 15 ft. Each bent whose height exceeds 10 ft. shall 

 be braced transversely and, if it exceeds 15 ft., shall in addition 

 be braced longitudinally in at least every fifth panel. 



286. Framed Trestles. For trestles of greater height than 

 30 ft. framed bents shall be used. They shall be supported upon 

 foundations of concrete piers, timber sills, or piles. All framed 

 bents shall be braced transversely and, in every alternate panel, 

 longitudinally. 



287. Trestle Stringers. Wherever there are several timber 

 stringers under each rail they shall be placed symmetrically 

 under same. The stringers shall break joints over the bents, 

 shall be securely fastened thereto, and shall be separated from 

 each other by means of cast-iron fillers one-half (i) in. thick 

 spaced not over 5 ft. apart. 



