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Citation |
Wen RK, Veletsos AS. Highw. Res. Board bull. 1962; 315: 1-26. |
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Copyright |
(Copyright © 1962, National Research Council (U.S.A.), Highway Research Board) |
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DOI |
unavailable |
PMID |
unavailable |
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Abstract |
RESULTS are presented of an analytical study of the dynamic behavior of simple-span highway bridges traversed by heavy vehicles. The factors considered include the speed of the vehicle, the spacing of the vehicle axles, the dynamic conditions of the bridge and the vehicle as the vehicle enters on the span, and the unevenness of the bridge surface. Representative bridges and vehicles were utilized and the effects of the parameters enumerated observed by varying one parameter at a time. The bridges considered are of the highbeam type with span lengths in the range between 20 and 78 ft. This type of bridge consists of a series of steel girders and a reinforced concrete slab. In the marjority of solutions the vehicle is represented as a two- axle loading. The magnitude of the maximum dynamic effects in a bridge increase with increasing vehicle speed. By varying the axle spacing while keeping all other variables constant, it was found that a quasi-resonance condition is developed when the time interval between the application of two axles over a point is equal to the fundamental natural period of vibration of the bridge. If the bridge is already in a state of oscillation when the vehicle enters the span, the dynamic effects produced by the vehicle depends on the timining of its entry with the oscillation of the bridge. The influence of the initial vehicle oscillation was investigated by considering both a bouncing and a pitching motion for the vehicle. The magnitude of the resulting dynamic effects were found to increase almost linearly with the amplitude of the initial oscillation considered. |