移动荷载作用下大跨度铁路斜拉桥纵向共振机理

Longitudinal resonance mechanism of a long-span cable-stayed railway bridge under moving loads

列车荷载作用下铁路斜拉桥将在不同方向上发生振动,列车竖向荷载作用下导致的主梁纵向振动将影响道床稳定性和伸缩装置的使用,甚至影响行车安全性和舒适性。采用等效纵向荷载研究移动荷载作用下斜拉桥纵向振动机理,推导纵向共振速度估算公式。以一大跨度铁路斜拉桥为实例,分析了不同速度的移动荷载作用下结构动力响应。结果表明,当移动荷载速度与估算纵向共振速度接近时,移动荷载通过桥梁时的纵向加载频率与桥梁一阶纵向振动频率接近,斜拉桥发生纵向共振现象,主梁和桥塔动力响应显著增大。

Under the moving train loads, a cable-stayed railway bridge generally vibrates in different directions. The longitudinal vibration of the bridge deck induced by the vertical trainloads may influence the stability of track bed and the usage of retractor devices, and may even affect the running safety and riding comfort of train. The longitudinal vibration mechanism of the cable-stayed bridge under moving loads is investigated by using the equivalent longitudinal loads. A formula for estimating the resonant speed of the cable-stayed bridge is developed. A long-span cable-stayed railway bridge is taken as an example to analyze the dynamic response of the bridge under moving loads at different speeds. The numerical results indicate that when the speed of the moving load approaches the resonant speed predicted by the formula, the longitudinal loading frequency excited by moving load approaches the first-order longitudinal natural vibration frequency of the bridge. Then, the longitudinal resonance of the cable-stayed bridge occurs and the dynamic responses of the deck and the towers increase significantly.