. Details of railroad truss-bridges . ommon among the railroads that do not per- 26. rait their designs to be governed by the specifications of thebridge companies. Cast-steel pedestals are more economical and morerigid than those built of steel shapes; but they are liable to be-come cracKed when subjected to shocKs or large eccentric loads. ROLLERS AND PLATES. In bridges over eighty feet in length,rollers must be used,in order that the expansion and contraction of the trusses,producedby changes of temperature,will not damage the bridge or the are two general types of rollers,the
. Details of railroad truss-bridges . ommon among the railroads that do not per- 26. rait their designs to be governed by the specifications of thebridge companies. Cast-steel pedestals are more economical and morerigid than those built of steel shapes; but they are liable to be-come cracKed when subjected to shocKs or large eccentric loads. ROLLERS AND PLATES. In bridges over eighty feet in length,rollers must be used,in order that the expansion and contraction of the trusses,producedby changes of temperature,will not damage the bridge or the are two general types of rollers,the circular rollers,and thesegmental rollers. shows a nest of circular rollers,which rest directlyupon the masonry plate. The masonry bed-plate and the shoe-plate ofthe pedestal have narrow plates attached to their bearing surfaces;which fit into the grooves in the rollers. The Z-bars on the sideshold the rollers in place and prevent lateral movement of the ped-estal. The angles at the ends tend to prevent dirt from getting in-.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttheses, bookyear1910
