大跨度预应力混凝土连续梁桥徐变效应分析

Creep Effect Analysis of Long Span Prestressed Concrete Continuous Beam Bridge

目的对大跨度预应力混凝土连续梁桥的徐变效应展开研究,以预测自然环境中变化温湿度情况下混凝土的徐变效应。方法依托香格里拉金沙江礼仁大桥为工程背景,结合桥址的环境特征及桥梁设计上的特点,采用Madis/Civil有限元计算软件建立该桥的模型,选取《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTG 3362—2018)对混凝土收缩徐变的计算模式作为标准,对变化温度、湿度条件下混凝土的收缩徐变计算模型进行改进,利用改进的计算模型对该桥进行施工控制。结果通过对比有限元模型计算的挠度、内力及应力理论计算值与现场实测值的结果分析,在桥梁最大悬臂梁施工阶段以及成桥阶段,桥梁挠度理论计算值与实测值数值相近,总体满足工程精度要求;在成桥后,混凝土收缩徐变对预应力混凝土构件轴力影响较小,但对结构弯矩影响较大。结论合龙后桥梁线形满足设计要求,验证了改进模型的准确性,为自然环境中大跨度PC连续梁桥徐变效应的分析提供了参考。

The creep effect of long-span prestressed concrete continuous girder bridge is studied to predict the creep effect of concrete under the condition of changing temperature and humidity in natural environment.Based on the engineering background of Liren Bridge on Jinsha River in Shangri-La,combined with the environmental characteristics of the bridge site and the characteristics of bridge design,the model of the bridge is established by using Madis/Civil finite element calculation software.The calculation model of concrete shrinkage and creep in China′s′Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts′(JTG 3362—2018)is selected as the standard.The calculation model of shrinkage and creep of concrete under changing temperature and humidity conditions is improved,and the improved calculation model is used to control the construction of the bridge.By comparing the deflection,internal force and stress calculated by the finite element model with the measured values in the field,the results are analyzed.In the construction stage and the completion stage of the maximum cantilever beam of the bridge,the theoretical calculation value of the bridge deflection is similar to the measured value,which generally meets the engineering accuracy requirements.After the completion of the bridge,the shrinkage and creep of concrete have little effect on the axial force of prestressed concrete members,but have a great influence on the bending moment of the structure.The alignment of the bridge after closure meets the design requirements,which verifies the accuracy of the improved model and provides a reference for the analysis of creep effect of long-span PC continuous beam bridge in natural environment.