大跨度斜拉桥倒Y形混凝土桥塔的横向拟静力试验

Lateral quasi-static test of inverted Y-shaped concrete tower for long span cable-stayed bridges

为研究强震下大跨度斜拉桥倒Y形混凝土桥塔的横向破坏机理及屈服后性能,文中以苏通大桥为背景,基于OpenSees平台建立了有限元分析模型,根据动力特性等效和恒载轴力等效原则将全桥模型简化为单塔模型,并确定了两点位移加载模式,采用1:35的几何缩尺比设计了试验模型并进行拟静力推倒试验,最后结合数值模拟分析,得到地震下桥塔的屈服顺序和破坏位置,并分析屈服后性能。研究结果表明:提出的简化单塔模型可替代全桥模型进行横向地震破坏机理研究;在横向强震下,横梁上侧塔柱截面最先屈服,塔底截面其次屈服,横梁下侧塔柱截面最后屈服,最后破坏位置为横梁上侧塔柱或塔底截面;在塔柱截面屈服后,桥塔整体强度增幅明显,破坏位移可达屈服位移的4~6倍,具有延性破坏特性;塔柱截面配箍率的增加会显著增大桥塔的整体强度和位移能力。

To study the lateral failure mechanism and elastic-plastic performance of inverted Y-shaped concrete towers for long span bridges under strong earthquake, the Sutong Bridge was taken as a prototype and its finite element model was established using Open Sees platform. According to the equivalent principle of dynamic characteristics and the internal forces of key sections under dead loads, the full-scale bridge model was simplified to be a single-tower model. Meanwhile, time-history analyses were conducted to determine the displacement-based two-point load pattern. Then, a 1：35 scale specimen of the simplified single-tower was constructed to perform a quasi-static pushover test using the displacement-based two-point load pattern. Finally, based on the test results and numerical analyses, the yielding order and failure positions as well as the inelastic performance of the concrete tower in the transverse direction were obtained. The results show that the simplified single-tower model can be used to represent the full-scale bridge model for the study of lateral seismic failure mechanism. Under lateral strong earthquakes, the column section above the crossbeam firstly yields, followed by the bottom section of the tower and then the column section below the crossbeam. The failure position of the concrete tower can be the column section above the crossbeam or the bottom section of the tower. A large post-yielding strength of the tower was observed, whereas the failure displacement can be 4~6 times of the yielding displacement. It is also found in this study that the increase of transverse reinforcement ratio can obviously improve the global strength and displacement capacity of the tower.