A treatise on mountain roads, live loads, and bridges - Softcover

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1879 Excerpt: ...Thus, the live-load should be multiplied by, in order to bring them both to similar conditions. This fraction is generally V for timber, $ for iron, and f for masonry. Live-loads on bridges may be classified as follows:--Firstly.--The live-load of a weight per foot-run of road-way. Secondly.--The live-load of a weight per square-foot of road-way. The abovementioned live-loads are readily reduced to dead-loads. Thirdly.--The live-load of a single moving-load, such as a road-roller, or vehicle on two wheels. Fourthly.--The live-load comprised of two or more loads moving at fixed distances apart longitudinally; such as steam-rollers, elephants, vehicles on four wheels, trains of vehicles. The last two descriptions of live-loads require reduction to dead-load by calculation; for the greatest bendingmoment is produced when the heaviest portion of a combined load is at the centre of a span, and as the heaviest load approaches the point of support, this moment is reduced, and finally vanishes. To compare these several live-loads they must be reduced to similar terms. Case I.--To compare the live-loads, st load, per foot-run of road-way. 2nd load, per square-foot of road-way. The loads being fixed, the width of the road-way second load will vary. Let Z = tons per foot-run of road-way. W = lbs. per foot-square of road-way. / = span. B ss width of road-way in feet. When the width of road-way in any example exceeds B in this equation, Z and IV, being given, the live-load of a square-foot of road-way is greater than the live-load of the load per foot-run. When the width of road-way in any example is less than B, the load per foot-run is the heaviest live-load. Case 2.--To compare the live-loads, st load, per foot-run of road-way. 3rd load, a single rolling weight. Thew...