西部山区桥梁双柱墩损伤控制与抗震设计理论研究

Double-column piers are widely employed in highway bridges in the mountainous area, and seismic hazard is higher in western China. Many double-column piers suffered severe damage in the Wenchuan earthquake where the intensity is more than 9, and their seismic performance and damage controlling need to be improved. This project will focus on the related theory and experimental study to improve the performance of double-column piers by using buckling-restrained braces (BRBs) based-on the concept of structural fuse and damage control. Firstly, the general rule of response and design response spectra of structure with fuse is developed by nonlinear time history analysis based-on the proposed inelastic spectra for structures with fuse. Secondly, the proper design parameters (the length of the BRBs core), considering the structural features of mountain double-column piers such as foundation deformation, bent cap flexibility and difference of piers height, are derived. Thirdly, The displacement-based design method of double-column piers with BRBs is developed based-on the design philosophy of structural fuse and damage control. And then the seismic performance and failure mechanism of double-column piers with BRBs investigated by quasi-static test, substructure hybrid test, and numerical simulation, the effect of structural damage control is also verified. Finally, the seismic performance of the whole bridge structure is studied, and its performance-based design method is also developed.

双柱式桥墩在公路桥梁中应用广泛，而我国西部地区破坏性地震频发、地震危险性较高，汶川地震中IX度及以上强震区双柱墩震害比较严重，双柱墩的损伤控制和抗震能力提升等问题亟待解决。本课题基于“保险丝”的设计理论，采用防屈曲支撑(BRB)作为保险丝，实现双柱墩的损伤控制；基于建立的设置保险丝体系的弹塑性反应谱模型，分析该体系在远场和近断层地震动下地震反应的普遍规律，并拟合得到设计反应谱公式；考虑基础变形、盖梁柔性、墩高差异、柱间系梁等山区双柱墩结构特点，确定BRB合理设计参数并建立双柱墩的损伤控制设计方法；通过拟静力试验和子结构混合试验并结合数值模拟，揭示双柱墩的破坏机理、检验损伤控制体系的效果、探索整个桥梁结构的破坏过程；通过数值模拟分析优化双柱墩损伤控制设计、考察全桥结构的抗震性能，并发展全桥结构横桥向的基于性能(位移)抗震设计方法，最终实现复杂地震动作用下山区桥梁双柱墩及其桥梁的损伤控制。

桥梁双柱墩在国内外中小跨径公路桥梁和城市高架桥中应用非常广泛，但在历次破坏性地震中震害普遍严重，如汶川地震强震区(IX~XI度)区域内的双柱墩出现严重破坏和完全失效的比例分别达到20%和40%。本课题基于“保险丝”的设计理论，采用防屈曲支撑(BRB)作为保险丝，研究了设置人字形、单斜式和肘节式BRB保险丝体系在对双柱墩的损伤控制和减震效果，推导出由桥墩材料、几何属性和位移放大系数等无量纲参数控制的BRB核心段长度取值范围表达式，以及确定其影响抗震性能的核心控制参数及其取值范围。发展设置保险丝体系的弹塑性反应谱模型，统计得到保险丝体系在远场和近断层地震动下反应谱的普遍规律，并拟合得到设计反应谱公式，可为保险丝体系的地震需求提供依据。提出装配铅阻尼器(RSC-LEDs)、钢管组合构件的摇摆-自复位双柱墩体系，发展多弹簧摇摆-自复位双柱墩模拟方法并通过拟静力试验进行验证。采用析因分析法研究了各关键设计参数对桥墩滞回性能的影响程度，对比讨论了耗能钢筋对桥墩性能的影响，定性分析了阻尼器出力、初始预张拉力、无粘结预应力筋配筋率、上部结构重量及盖梁-墩柱刚度比对RSC-LEDs双柱墩滞回性能的影响。在设计理论方面，结合中国公路规范、基于位移的设计方法、基于等能量的设计流程，发展了设置不同形式(人字形、单斜式和肘节式)保险丝体系的双柱墩基于位移的抗震设计方法，还提出了一种适用于RSC-LEDs双柱墩体系的两阶段抗震设计方法。本课题针对山区桥梁双柱墩的特点，系统、深入地研究了其损伤控制措施及其设计方法，可为解决双柱墩的损伤控问题提供理论支撑。