随机变温作用下徐变对预应力混凝土梁桥结构行为的影响  

Effect of Creep on PC Girder Bridge Structural Behaviors under Randomly Changed Temperature

作　　者：鲁薇薇[1] 杨永清[1] 李晓斌[1] 

机构地区：[1]西南交通大学土木工程学院,四川成都610031

出　　处：《公路交通科技》2017年第12期82-89,共8页Journal of Highway and Transportation Research and Development

基　　金：国家自然科学基金项目(51508474);铁道部科技研究开发计划重大课题项目(2008G031-K)

摘　　要：结合在自然环境条件下开展徐变试验和既有研究成果,对现有可考虑温度影响的徐变模型包括Fahmi提出的基于时间-温度等效原理的徐变模型、CEB-FIP(1990)模型、BP模型、B3模型和组合徐变模型进行比选,并将比选出的组合徐变模型应用于预应力混凝土梁桥的徐变效应分析中。假定徐变符合弹性徐变理论,基于初应变法解决了应用组合徐变模型进行桥梁结构徐变效应分析的问题。通过将基于组合徐变模型和依据我国公路04桥规分析得到的桥梁结构变形、应力和预应力损失结果进行比较,探究忽略实际变温对徐变影响可能导致的桥梁结构行为估算偏差。研究结果表明:考虑实际环境变温影响的徐变系数预测值与试验值更为贴近,现行徐变模型因未计入环境变温影响,可能低估了冬季和春季浇注混凝土的徐变,高估了夏季和秋季浇注混凝土的徐变;在考虑自然环境温度影响的徐变作用下,梁体下挠度可较规范值大约15.5 mm,截面应力与规范值的最大相对偏差约为10%,预应力损失可较规范值大约40%以上。随机变温作用下混凝土徐变,加剧了桥梁梁体持续下挠、混凝土开裂和预应力损失等问题。因此,在桥梁结构设计中推荐采用组合徐变模型计入实际环境变温对结构混凝土徐变行为的影响,从而为预应力束的合理布置与张拉控制、梁体预拱度的准确设置等方面提供参考。The existing creep prediction models in randomly-changed temperature conditions are compared and selected by using the obtained research results and the experimental study on creep of concrete under natural environment condition, including the creep model proposed by Fahmi based on Time-shift equivalence principle, CEB-FIP （1990） model, BP model, B3 model, and combined creep model. The selected combined creep model is applied in the creep effect analysis of prestressed concrete bridges. Based on the elastic-creeping theory and the initial strain method, the combined creep model could be applied to analyze the creep effect of concrete bridges. In order to investigate the calculation deviation of bridge structural behaviors caused by neglecting the effect of actual temperature change on creep of concrete, the analysis results of deformation, stress and prestress loss of prestressed concrete bridge based on combined creep model and the Chinese current 04 highway bridge specification are compared. The research result indicates that （ 1 ） The predicted creep coefficients considering the mutative environment temperature match better with the experimental creep coefficients. The creep model which is independent on the ambient temperature may underestimate the creep of concrete cast in winter and spring and may overestimate the creep of concrete cast in summer and autumn. （2） In contrast with the current specification, the concrete creep with considering the effect of environment temperature variations may lead to the girder deflection increased by 15.5 mm and the prestress loss increased by more than 40%, and may also resulting in the relative deviation between calculated and specified sectional stresses up to 10%. （3） The creep behavior of concrete under randomly changed temperature leads to an increase of the deflection, concrete cracking, and prestress loss of bridge structures. In the design of concrete bridge, the combination creep model is recommended for considering the effect of environmental tem

关 键 词：桥梁工程 徐变效应分析 组合徐变模型 预应力混凝土梁桥 随机变化温度 

分 类 号：U448.35[建筑科学—桥梁与隧道工程] U441.5[交通运输工程—道路与铁道工程]