to move longitudinally under changes of temperature, 

 they shall be anchored against lifting or moving side- 

 ways. 



1 20. All bridges shall be cambered by giving the panels cumber, 

 of the top chord an excess of length in the proportion of 



| of an inch to every ten feet. 



121. The lower struts in trestle towers must be capable Trestle Tower*, 

 of resisting the strains due to changes of temperature or of 

 moving the tower pedestals under the effects of expansion 



or contraction. 



For high or massive towers, these lower struts will be 

 securely anchored to intermediate masonry piers, or the 

 tower pedestals will have suitably placed friction rollers, 

 as may be directed by the Engineer. 



122. All joints in the tower columns shall be fully spliced 

 for all possible tension strains, and to hold the parts firmly 

 in position. ( 25, 69.) 



123. Tower footings, pedestals and bed-plates must be 

 planed on all sliding surfaces ; and the holes for anchor 

 bolts slotted to allow for the proper amount of movement. 

 ( 28.) 



124. All workmanship shall be first class in every par- w t 

 ticular. 



125. All eye-bars must be made of Medium Steel. ( 

 138-142.) 



126. Eye-bars, all forgings and any pieces which have E>C Bar,, 

 been partially heated or bent cold must be wholly an- 

 nealed. Crimped stiffeners need not be annealed. 



127. No reliance will be placed upon the welding of 

 steel. 



128. No sharp or unfilleted angles or corners will be 

 allowed in any piece of metal. 



129. The steel ( 138-144) may be used in tension with- Ra>min C . 

 out reaming of punched holes up to f inch in thickness, and 



may be used in compression without reaming for all thick- 

 nesses of metal which will stand t ting test. ($ 146.) 

 In all other cases, the steel must have all holes drilled 

 or reamed to a diameter inch larger than the punched 

 holes. 



