Evening Republican, Volume 14, Number 188, Rensselaer, Jasper County, 9 August 1910 — SHORTENS LIFE OF BRIDGE [ARTICLE]

SHORTENS LIFE OF BRIDGE

Effect of Smoke on Structure Is Just Now Engaging the Attention of Engineers. When a locomotive la making speed against a grade with. Its full complement of cars and tonnage behind It, the blast from the smokestack may attain almost explosive force. But regardless of how many pounds dead weight might be blown from the stack, Its corrosive and heat effects in passing under bridge and viaduct structures have been under careful study by engineers. The “Cotton Farm" bridge In Boston was built In 1896 with a clearance of only fifteen set above the line of the Boston & Maine road. The floor of the bridge was supported by hollow tile arches, resting upon flanges of steel “I" bearqs. These steel beams were protected by heavy lead plale and above were rendered rust proof by cement tiles. In ten years the locomotive blast had eaten into the lead shewing and into the tiling to such extent that much of the coating fell to the ground and all of it had to be torn out. At another point In Boston'" is a bridge spanning the road where locomotives In one direction take a heavy grade in passing. The height of the clearance is 18 feet, while the bridge has only wooden stringers. On the up grade end of the bridge, where forced blast is necessary, the stringers are eroded and burned to a depth of a quarter Inch; on the down grade end, damage is not noticeable. The judgment of the engineers Is that 18 feet clearance allows of a cheaper bridge and a longer life to It than the more costly structure at the minimum of 15 feet.