超大跨斜拉桥横向地震破坏模式与损伤控制分析

地震作用下控制结构合理的破坏模式是保证其震后安全性的基础，而目前对超大跨度缆索桥梁破坏模式及其控制的研究仍显不足。以一座试设计的主跨1400m斜拉桥为例，采用弹塑性分析方法并引入地震损伤指标研究了地震作用下横向约束体系的地震损伤与破坏模式；为提高结构的整体抗倒塌能力，研究了极端地震作用下损伤控制策略对桥梁地震损伤和破坏模式的影响；在此基础上，进一步研究了主塔上横系梁刚度和耗能能力以及附加耗能构件对主塔地震损伤分布的影响。结果表明：在横向极端地震作用下，主塔上、下塔柱区段几乎同时遭受损伤，发生双塑性铰的破坏模式；附加耗能阻尼器的损伤控制策略可显著控制桥墩的地震损伤，但不能完全有效控制主塔损伤；在优化参数的基础上，若在上塔柱区段附加一定数量的耗能构件，则可合理改善主塔的破坏模式使其满足地震损伤控制目标。

Seismic failure patterns and damage control of super long span cable-stayed bridges in transverse direction

Under earthquake loading, rational structural failure patterns are the basis for ensuring structures to survive. However, the studies on seismic failure patterns and their control were rarely reported in literatures especially for long span cable-supported bridges. In this paper, elasto-plastic analyses were carried out to investigate seismic damage and failure patterns by employing seismic damage indices for a trial designed cable-stayed bridge, which has a central span of 1400 m and is excited by various ground motion intensities. Damage control strategies were presented, by installing viscous dampers between the pylons and the girder as well as between the piers and the girder, which are expected to reduce the damage of structure and improve the capacity of collapse resistant. The influence of the damper allocations and coefficients on structural damage and failure pattern were studied under extremely ground motion (Peak Ground Motion Acceleration (PGA) =1.0g) in transverse direction of bridge. In addition, the influence of the stiffness of the supporting piers on structural seismic performance was also investigated. The effects of stiffness and energy dissipation capacity of the cross beam of the pylon were further discussed. Moreover, damage control counter measure installing energy dissipation components between the pylon legs was presented. The results show that the pylon top and bottom regions are simultaneously subjected to damage under extremely earthquake, indicating a failure pattern of double plastic hinges; the damage control strategies with additional dampers can effectively reduce the damage of piers, however, it is not effective enough to the damage of towers; the energy dissipation components installed between the pylon legs at the top region can improve the failure pattern of the pylon and the damage control targets based on seismic damage indices can be satisfied.