多室连续曲线箱梁剪滞效应地震反应分析

Seismic response analysis on shear lag effect of continuous curved box beam with multi cells

采用三维有限元数值仿真技术对曲线箱梁进行模态分析和地震动作用下时程分析以探讨多室连续曲线箱梁自振特性和剪力滞效应。分别建立单箱单室和单箱双室多跨连续梁空间板壳有限元模型,研究箱室数和曲率角对曲线箱梁自振频率的影响,在此基础上,对单箱双室连续曲线箱梁输入天津波以分析剪滞系数沿纵、横向分布规律。结果表明:箱室数和曲率角对自振频率影响较大,前5阶自振频率随着箱室数增加在增大,随着曲率角增加,自振频率一直在减小,且不同模型的结构前3阶振型特征各不相同;受地震动激励,多室箱梁翼板剪力滞效应显著,沿横向,剪滞系数在顶板与腹板交界处形成峰值,剪滞系数高达2.505,沿纵向,中间支座截面剪力滞效应较跨中截面严重;通过定义宽径比为主要变量,采用最小二乘法对剪滞系数进行回归分析,提出计算剪滞系数峰值的经验公式,与有限元误差不足2%,满足精度要求;

Modal Analysis and time-history analysis under seismic action are carried so as to investigate free vibration characters and shear lag effect of mutil cells continuous curved box beam 3 D finite element simulation technology. Spatial shell finite element models of single box single cell and single box double cells mutil-span continuous beams are respectively founded to study the influence of box-cell number and curvature angle on vibration frequency of curved box beam, on the basis of it, the distribution law of shear lag coefficients along longitudinal andtransverse direction of single box double cells continuous curved box beam is analyzed by inputting Tianjin seismic waves. The results indicate that box-cell number and curvature angle have a great influence on vibration frequency, top 5 of which are becoming larger with the increasing of box-cell number, while it decreases with the increasing of curvature angle,in addition,the top 3 modes traits of different structural models are different with each other; under seismic action, shear lag effects of mutil cells box beam flange are prominent, along transverse direction, shear lag coefficients reach its peak at the junction between web and upper flange, the maximum of it reaches 2. 505, along longitudinal direction, shear lag effectat mid-supports section is more prominent than that of mid-span section ;by defining web-radius ratio as main variate, regression analysis of shear lag coefficients is performed with least square method, and empirical formulas of peak shear lag coefficients are put forward, the error between empirical formulas and FEM is less than 2% ,which meets precision requirement