Dynamic Response Analysis Of Medium And Small Spanning Municipal Bridges In The Congested State

When traffic congestion occurs on municipal bridge, the vast majority of vehicles are under the idle state and the engine speed maintains in 600 to 800r/min(corresponding frequency of 10Hz~13.33Hz). Although the moving vehicle impact on bridge has shrunk at this time, the engine vibration is likely to excite lower natural frequency, causing resonance phenomenon and repairing bridge health. This paper studies the dynamic response of medium and small spanning municipal bridges in the congested state, which provides a scientific basis for the city bridge design, operation, maintenance and reinforcement.According to the survey data of urban traffic volume and the relevant literature, this paper draws up an equivalent vehicle load model including the static and dynamic parts, which is suitable for the bridge congestion. Then it discusses the structural resonance theory from different aspects and put up forward the dynamic analysis method and the concept of dynamic enlargement coefficient. By using finite element software, the static and dynamic response and modal characteristics of a continuous bridge can be calculated. Finally, based on some hypothesis and simplification, the influence of span and structural system on congestion dynamic response is studied.It is found that simple supported beam bridge is more advantageous to continuous beam bridge and continuous rigid frame bridge when bearing vehicle congestion load. One-way congestion brings more harm to bridges. As the bridge span becomes shorter, the dynamic response grows bigger and it’s more likely to excite the low-order natural mode of vibration. Therefore, when designing medium and small spanning municipal bridges, we should take into account the impact of traffic jam. Choosing simple beam system is more reasonable as conditions allow.