基于时变易损性的山区桥梁合理抗震体系研究

Since the Eleventh Five-Year Plan was applied, the main construction of highway,especially the freeway, tends to western mountain zones of China, thus, lots of mountain bridges were or are being built necessarily. Overall, the mountain bridges are characterized by high pier and significant stiffness difference in piers. However, there is not complete and specific seismic design guidance for these bridges in our country, what's more,the insufficiency of highway net in mountain zones lead to the essential of keeping the traffic unblocked which bridges are the key project, compared to the plain zones. In this project, we will base on the performance-based seismic design and resarch the reasonable Earthquake Resisting System from the viewpoint of time-dependent fragility. At the same time, we will show the effects of the mainly coupled parameters of the mountain high-pier structures on the precise dynamic bridge model with probability and propose the formulation of damage index. Then, we will obtain the seismic fragility curves of the mountain bridges,and the degradation model of material will be introduced to obtain the basic theory of the time-dependent fragility of the mountain bridges. and investigate the characteristics of the structure element of the mountain bridges and restrainers. Furthermore, to optimize and evaluate the reasonable seismic resistance of the mountain bridges, we will introduce the Monte-Carlo optimization theory and the system fragility indexes. Based on the above studies, we will propose the specific arrangement of the structure elements of the mountain bridges. Overall, this project will play an important role in the seismic designs of the mountain bridges, and assessment of the seismic performance of the built bridges.

自十一五以来，我国公路特别是高速公路的建设重心已向中西部山区倾斜，为此需建设大批山区桥梁。山区桥梁的特点是桥址谷深、墩高且墩间刚度变化大，对于这类极其特殊的桥梁，我国现有的抗震设计规范无法涵盖，而对于山区公路，由于没有完善的路网，地震后桥梁保通以抢救生命财产，相比平原区更为迫切，为解决这一难题，本项目将基于性能的抗震设计思想，从时变易损性角度研究山区桥梁的合理抗震体系，建立概率性的精细化动力分析模型，揭示山区高墩结构布置参数之间的耦合因素对易损性的影响规律，提出高墩结构损伤指标的计算方法，建立桥梁非线性动力易损性曲线，构建山区桥梁地震时变易损性分析方法；深入研究山区桥梁的传力路径和抗震单元受力特点，引入蒙特卡罗优化理论，以构件和系统易损性指标来优化和衡量山区桥梁的合理抗震体系，由此提出桥梁的抗震优化布局。上述科学问题的解决，将为指导山区桥梁的抗震设计、评估已建桥梁的抗震性能奠定坚实的基础

自十一五以来，我国公路特别是高速公路的建设重心已向中西部山区倾斜，为此需建设大批山区桥梁。山区桥梁的特点是桥址谷深、墩高且墩间刚度变化大，对于这类极其特殊的桥梁，我国现有的抗震设计规范无法涵盖，而对于山区公路，由于没有完善的路网，地震后桥梁保通以抢救生命财产，相比平原区更为迫切，为解决这一难题，本项目将基于性能的抗震设计思想，从时变易损性角度研究山区桥梁的合理抗震体系，取得了如下成果：（1）提出一种新的基于条件边缘乘积法（PCM）的系统地震易损性分析框架，基于该框架研究了弹性索对中等跨径斜拉桥的影响，揭示了常规斜拉桥惯性力及能量传递规律，提出斜拉桥合理弹性索设计方法；（二）从基于性能的抗震设计评估角度出发，采用易损性分析方法研究了山区高墩多塔斜拉桥地震响应规律，揭示了高墩斜拉桥特殊的损伤特征及失效模式，探究了不同减震方法对高墩斜拉桥的控制机理，进而提出了高墩斜拉桥合理抗震体系的设计思路。（三）建立混凝土内氯离子扩散规律，研究了氯离子对钢筋的侵蚀机理，确定钢筋锈蚀时间及钢筋力学特性时变曲线，提出了考虑氯离子侵蚀效应的桥梁时变地震易损性分析框架，揭示了山区高墩桥梁在服役期内抗震性能演变规律。（四）通过引入Nataf变换，结合基于样条变换的均匀设计响应面法，提出了一种综合考虑地震动、结构不确定性以及变量相关性的桥梁地震易损性分析方法，提高了传统易损性分析方法的计算效率及精度。(五) 基于简化的Kerr模型，建立了弹性地基梁的精细化模型，研究了弹性地基梁系统的非保守特性，揭示了土-结构相互作用二次弯矩的非线性本质。