基于精细化数值模拟的FPS隔震曲线桥抗震性能研究

A curved bridge is prone to occurring girder falling, pier bending and shearing failures and other serious earthquake damages. Due to the plane irregularities of the curved bridge, it's better to adopt the FPS bearing to control the relative displacements between pier and girder and reduce pier damage. But the existing researches lack of refinement numerical simulation method for curved bridge FPS system. It's hard to reveal the real seismic response characteristics and failure mechanism of the FPS isolation curved bridge under 3-D ground motion action. Based on this, first of all, this project will determined the constitutive model and its parameters of the FPS bearings considering bi-directional coupling effects through comparison between the experimental study and the numerical simulation study; Secondly, a refined numerical simulation model of curved girder and its adjacent girders will be built, the explicit dynamic analysis will be done considering seismic pounding effects, by which the pounding stiffness and damping parameters of the contact elements can be determined. Then a refinement numerical model method consider the uneven distribution of pounding effect in curved bridges can be given; Thirdly, the seismic performance of the FPS isolation curved bridges under 3-D ground motion excitation will be studied herein. Based on the seismic fragility curves calculated by the adaptive Pushover analysis, the evaluation index based on the decreasing amplitude ratio in key parts will be discussed. Finally, the influences factors such as geological conditions, geometry conditions, structure parameters and their influences on the seismic performance of FPS isolation curved bridge will be analysis herein, then the application scope and service conditions of the FPS bearing applied in curved bridge can be concluded. Therefore, the project will provide theoretical basis and technical support for earthquake resistant control theory and aseismic design theory of the curved bridges.

曲线桥梁易于发生落梁、墩柱弯剪破坏等严重震害，由于其平面不规则，宜采用FPS隔震支座控制墩梁相对位移、降低墩柱损伤。但现有研究缺乏对曲线桥FPS隔震体系的精细化数值模拟，难以揭示该类曲线桥真实的地震反应特点和损伤破坏机理。基于此，本项目拟首先通过试验研究与数值模拟的对比，确定FPS支座在动轴力及双向耦合受力下的本构模型和计算参数；其次对相邻联碰撞条件进行精细化数值模拟，利用显式动力分析确定接触单元碰撞刚度及阻尼参数，提出考虑曲线桥非均匀碰撞的精细化模拟方法；然后，开展三维地震输入下FPS隔震曲线桥的抗震性能研究，利用自适应推覆分析获得的地震易损性曲线，确定曲线桥关键减震率评价指标；最后，探讨地质条件、几何条件、结构参数、碰撞条件等因素对该体系抗震性能的影响，综合评价曲线桥FPS隔震体系的适用范围、限制条件。本课题将为我国城市曲线桥梁的抗震设计及减震控制理论提供理论基础和技术支持。

在历次大地震中，诸多曲线桥梁发生了落梁、墩柱弯剪破坏、整体垮塌等震害。其原因主要有：一、曲线桥地震反应规律复杂，因而真实地震作用下桥梁往往发生预估之外的反应。二、减隔震支座缺乏理论与实验相结合的精细化模拟方法，难以在曲线桥中广泛使用。针对以上问题，本项目选取典型曲线桥为研究对象，针对不同参数曲线桥（圆心角67°~0°、跨宽比2.78~1.67、桥墩长细比3.0~7.6）进行数值模拟分析。选取6个摩擦摆支座（FPS）开展双轴耦合拟静力试验与数值模拟研究。最后取一实际震害曲线桥案例进行数值模拟分析，探讨曲线桥FPS隔震体系的适用范围。主要内容有：.1.以典型曲线桥为研究对象，采用OpenSEES平台，针对不同上部结构、下部结构，采用三种不同建模方法探讨针对不同曲率半径、桥宽、墩柱高度、墩柱形式曲线桥的高效准确抗震建模方法，为曲线桥抗震性能研究提供建模方法依据。.2.考虑到双轴耦合效应、摩擦系数是影响FPS支座减隔震性能的主要参数，制定不同加载速度、轴压力、双轴耦合加载方式的试验方案，通过试验获得FPS支座屈服力、回复力、摩擦系数、滞回性能、耗能能力等力学参数，分析对比获得加载速度，轴力，双轴耦合效应对支座性能的影响规律。基于OpenSEES平台建立数值对比模型，确定简化精确的数值模拟方法及参数选取原则，实现精细化数值模拟。.3.考虑相邻联周期、伸缩缝间隙、主梁刚度是影响相邻联碰撞的主要规律，制定不同碰撞刚度、相邻梁周期比、间隙值影响的数值模拟对比方案，通过数值模拟获得曲线桥墩柱内力、碰撞力等的影响规律。.4.对某一实际发生震害的曲线桥，依据以上研究结果建模并进行地震反应分析，获得桥梁地震反应规律，并将结果与实际震害进行对比。同时对该桥采用FPS支座，并进行数值模拟，验证FPS支座能有效减小桥梁震害，降低震后桥梁修复难度。.本项目探究并提出了针对不同形式曲线桥梁的精细化数值模拟方法，并通过试验分析确定了考虑FPS支座双轴耦合效应的精细化数值模拟方法。为曲线桥梁的设计者奠定了基础。

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