大跨有推力钢桁拱桥的地震反应特征与损伤控制

The large-span steel truss arch bridge with the thrust is widely used in the western mountainous areas in China, especially suitable for the “V” shaped Canyon area. Because of the numerous members and complex structures, seismic response of the structure also affected by the earthquake excitation mode and higher modes is very complex. In view of structural and mechanics characteristic of the large-span steel truss arch bridge with the thrust, this subject intends to study the mechanism and distribution of the seismic response of the structure, the seismic performance evaluation method based on fragility analysis, and the reasonable damping system. The contents include：(1)The main characteristics and influence mechanism of the seismic response of the steel truss arch bridge under the excitation of complex ground motions (including multi-dimensional excitation and multi-support seismic excitation) are studied. (2)Put forward damage index of the main component of the steel truss arch bridge, and establish seismic fragility curves of main components and system by using the probabilistic seismic demand analysis method so as to determine the seismic weak parts. (3)Seismic mitigation and isolation scheme at the pier top cannot be implemented because the bearing is not needed between superstructure and substructure in this bridge type. In order to effectively control the damage degree of vulnerable components, Buckling-Restrained Braces(BRB) will be set in the internal structure and used as dissipative member to take seismic fuses. The subject intents to carry out the reasonable damping system suitable for large-span steel truss arch bridge with thrust.

大跨度有推力钢桁拱桥是我国西部山区广泛应用的桥梁结构形式，尤其适用于V形峡谷地区。因其杆件众多、结构复杂，同时受地震动激励方式及高阶振型的影响，结构地震反应极为复杂。针对有推力钢桁拱桥的结构特点及受力特征，本课题拟从大跨度钢桁拱桥地震反应的影响机理及分布规律、基于易损性的抗震性能评估方法及有推力钢桁拱桥的合理减震体系三个角度展开研究。具体研究内容包括：⑴研究复杂地震动激励下（包括多维输入及多点激励）钢桁拱桥主要构件的地震反应主要特征与影响机理；⑵提出钢桁拱桥主要构件的损伤评价指标，采用概率地震需求分析方法建立拱桥主要构件及系统的地震易损性曲线，确定其抗震薄弱部位；⑶该桥型在上、下部结构之间因不需设置支座，导致墩顶减隔震方案无法实施。拟在结构体系内部引入BRB耗能构件，提出适合于大跨有推力钢桁拱桥的合理减震体系，有效控制易损构件的损伤程度。

大跨度有推力钢桁拱桥是我国西部山区广泛应用的桥梁结构形式，尤其适用于V形峡谷地区。因其杆件众多、结构复杂，同时受地震动激励方式及高阶振型的影响，结构地震反应极为复杂。针对有推力钢桁拱桥的结构特点及受力特征，本项目从大跨度钢桁拱桥地震反应的影响机理及分布规律、基于易损性的抗震性能评估方法及有推力钢桁拱桥的合理减震体系三个角度展开研究。基于振型分解反应谱法原理，采用动力与静力分析相结合的方法，提出了高阶振型引起结构地震反应的分离方法。该方法可为高、柔结构的高阶振型影响机理研究提供参考。提出了一种分离行波效应作用下拟静力分量和动力分量的可行方法。基于位移输入，应用逐步积分法求解结构总反应。基于位移输入，忽略结构质量及阻尼效应，应用逐步积分法求解结构拟静力项。利用RMM法的基本理论，从结构总反应中减去拟静力项即可得到动力项。该方法可为大跨桥梁的行波效应影响机理研究提供参考。提出了考虑主要、次要构件的权重的优化串-并联模型，并推导了计算公式，该模型更能真实地代表结构的实际失效模式。针对大跨有推力钢桁拱桥，系统研究了高阶振型、行波效应、多维激励、地震易损性以及合理减震体系。对于轴力和弯矩，在L/8区域～拱脚区域内，高阶振型对结构地震反应的影响显著。行波效应将使拱顶弦杆轴力显著增大，行波效应对拱顶区域上弦杆易损构件的中等损伤超越概率影响显著，一致激励可能会明显低估其超越概率值。设置BRB构件后典型代表性构件的损伤超越概率均有不同程度的减小，减震效应显著。本项目的研究结论可为同类桥型的抗震设计提供参考。