超高墩对山区三塔斜拉桥力学响应的影响

Influence of Ultra-high Piers on Mechanical Response of Three-pylon Cable-stayed Bridge in Mountain Area

摘要:

多塔斜拉桥是跨越宽阔水面和山谷的一种可行方案。然而，山区多塔斜拉桥的超高桥墩会改变全桥结构的整体刚度，使其力学响应有别于普通的多塔斜拉桥。为研究超高墩对三塔斜拉桥力学行为的影响程度，以某在建的超高墩三塔斜拉桥为例，首先确立了力学响应指标和计算方法，然后分析了桥墩高度、桥墩高差、主梁刚度和主塔刚度对塔顶位移、墩底弯矩、跨中挠度等结构响应的影响规律。结果表明：当桥墩高度增加时，车道荷载和温度荷载所引起的墩底附加弯矩会随之减小，而塔顶的纵向位移和主梁的跨中挠度随之增大；桥墩高差对桥墩的内力影响很大，高差较大时，矮墩会承受更多的弯矩；提高主塔刚度能够更有效的控制结构位移。

Abstract:

The multi-pylon cable-stayed bridge is a feasible scheme for spanning wide rivers and valleys. However, the ultra-high piers of multi-pylon cable-stayed bridges in mountainous areas can decrease the overall stiffness of the bridge structure, which makes its mechanical response different from those of ordinary multi-pylon cable-stayed bridges. To study the influence of ultra-high piers on the mechanical behaviour of three-pylon cable-stayed bridge in deep and wide valleys, a typical three-pylon cable-stayed bridge under construction is taken as an example. The index and calculation method for mechanical response are firstly established. Then, the effects of the pier height, pier height difference and stiffness of girder and pylon on the displacement at the top of the pylon, bending moment at the bottom of the pier and deflection at the mid-span are analyzed. The results show that: when the pier height increases, the additional bending moment at the bottom of the pier caused by the traffic lane load and the temperature decreases while longitudinal displacement at the top of the pylon and deflection at the mid-span of the girder increase; the difference of the pier height has a great influence on the internal force of the pier and the lower pier will bear more bending moment; the structural displacement can be better controlled by increasing the stiffness of the pylon.