Π型叠合梁斜拉桥建造全周期静风失稳模式及机理研究  

A full-cycle aerostatic instability model and the mechanism ofΠComposite girder cable-stayed bridges

作　　者：薛晓锋[1] 吕盛昌 曹体锁 高广中 XUE Xiaofeng;L Shengchang;CAO Tisuo;GAO Guangzhong(School of Highway,Chang’an University,Xi’an 710064,China)

机构地区：[1]长安大学公路学院,西安710064

出　　处：《振动与冲击》2023年第20期204-213,共10页Journal of Vibration and Shock

基　　金：国家自然科学基金(51808052);陕西省自然科学基金(2021JM-168)。

摘　　要：为了研究低抗扭转刚度斜拉桥建造全周期的静风稳定特征,采用风洞试验获得施工、运营阶段±10°风攻角区间主梁静风三分力系数,结合有限元数值模拟方法,采用内、外双层迭代算法同时计入斜拉桥几何非线性和风荷载非线性,对主跨跨径为480 m的Π型钢混叠合梁斜拉桥进行了建造全周期非线性静风响应分析。追踪该桥各典型施工阶段主梁变位和拉索索力随风速的变化,以揭示低抗扭刚度斜拉桥建造运营全过程中的静风失稳模式及失稳机理。分析结果表明:随施工阶段发展,静风失稳模式多次变化;各工况下的静风失稳均是三向变位的复杂耦合行为,本桥扭转和竖向变位交替占主导地位;最大单悬臂阶段为各施工阶段中最不利的一个工况,其失稳风速仅为72 m/s且结构响应较大。扭转为主导的失稳是由于拉索系统的应力降低而引起的结构破坏,而竖向变位为主的失稳是由结构较大变位引起的整体刚度的丧失导致的。静风失稳的内在机理是结构在风载下的附加风攻角反作用于风荷载使升力和升力矩迅速变化,同时结构的非线性变形导致拉索系统应力降低和结构刚度降低使结构破坏。In order to study the static wind stability characteristics of the cable-stayed bridge low torsional stiffness in the whole construction cycle,a wind tunnel test was used to obtain the static wind three-component force coefficient of the main girder in the range of±10°wind attack angle during the construction and operation stages.The layer iterative algorithm takes into account both the geometric nonlinearity and wind load nonlinearity of the cable-stayed bridge,and the full-cycle nonlinear static wind response analysis of theΠ-section steel composite beam cable-stayed bridge with a main span of 480 m was carried out.The changes of the main beam displacement and the cable force with the wind speed in each typical construction stage of the bridge were tracked to reveal the static wind instability mode and instability mechanism during the construction and operation of the low torsional stiffness cable-stayed bridge.Analysis results show that:with the development of the construction stage,the static wind instability mode changes many times;the static wind instability under each working condition is a complex coupling behavior of three-way displacement,and the torsion and vertical displacement of the bridge are alternately dominant.The largest single cantilever stage is the most unfavorable working condition in each construction stage,and its instability wind speed is only 72 m/s and the structural response is large.Torsional-dominated instability is caused by structural failure due to stress reduction in the stay-cable system,while vertical-deflection-dominated instability is caused by loss of overall stiffness due to larger deflections of the structure.The internal mechanism of static wind instability is that the additional wind attack angle of the structure under wind load reacts to the wind load,causing the lift force and lift moment to change rapidly.At the same time,the nonlinear deformation of the structure leads to the decrease of the stress of the cable system and the decrease of the structural stiffness,

关 键 词：桥梁工程 斜拉桥 静风稳定 施工过程 失稳模式 失稳机理 

分 类 号：U448.27[建筑科学—桥梁与隧道工程]