HIGHWAY BRIDGES 25 



102. Anchor Bolts. (See Par. 46.) 



103. Camber. All through truss bridges shall be given 

 a camber by making the panel length of the top chords, or their 

 horizontal projections, longer than the corresponding panels 

 of the bottom chord in the proportion of J in. in 10 ft. 



104. Temperature. Provision shall be made for a free expan- 

 sion and contraction of all parts, corresponding to a variation 

 of 150 F. in temperature. 



For bridges less than 80 ft. in length one end shall be free 

 to move upon smooth surfaces. 



Bridges of 80 ft. and over, resting on masonry, shall have 

 hinged bolsters or shoes at both ends, and at one end the shoes 

 shall rest upon a nest of turned expansion rollers, of not less than 

 4 in. in diameter (Par. 69), moving between planed surfaces. 

 (Par. 86.) 



In very high trestle towers one foot shall be fixed, two feet 

 shall be fixed in one direction only, and the fourth shall be free 

 to move in both directions. 



