既有桥梁卸荷-加载时下部结构承载力变化规律

Variation law of bearing capacity of lower structure under unloading-loading of existing bridge

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摘要为了得到既有旧桥上部结构拆除重建时,下部结构承载力变化规律,对山西省一座桥梁进行建模分析,采用有限元方法模拟拆除旧梁,安装新梁过程,分析不同的拆除步序对混凝土盖梁应力值与反拱值的影响,分析结果表明:盖梁卸载过程中这两项数值随盖梁上部荷载总重减小而增大,主梁完全卸载后,盖梁最大反拱值可达5.2mm,最大拉应力达4.9MPa,盖梁存在因反拱过大而导致结构开裂的风险。采取旧梁分跨拆除可有效控制这一风险,最大反拱值减小至2.2mm,最大拉应力减小至2.2MPa。因此主梁拆除与安装原则为:减少盖梁上部主梁空缺,保持盖梁为承载状态,在拆除旧梁后应尽快安装新梁,采用拆一跨装一跨施工方式,可以有效的控制盖梁反拱值和应力值在合理范围内。 In order to obtain the variation law of the bearing capacity of the substructure when the superstructure of the existing old bridge is demolished and reconstructed,a bridge in Shanxi Province is modeled and analyzed.The finite element method is used to simulate the process of demolishing the old beam and installing the new beam,and the influence of different demolition steps on the stress value and inverted arch value of the concrete bent cap is analyzed.The analysis results show that the two values increase with the decrease of the total load weight of the upper part of the bent cap during the unloading process of the bent cap.After the main beam is completely unloaded,the maximum inverted arch value of the bent cap can reach 5.2 mm,and the maximum tensile stress can reach 4.9 MPa.The bent cap has the risk of structural cracking due to excessive inverted arch.This risk can be effectively controlled by removing the old beam span by span.The maximum inverted arch value is reduced to 2.2 mm,and the maximum tensile stress is reduced to 2.2 MPa.Therefore,the principle of demolition and installation of the main beam is to reduce the vacancy of the upper main beam of the capping beam,keep the capping beam in the bearing state,install the new beam as soon as possible after the demolition of the old beam,and adopt the construction method of dismantling one span and installing one span,which can effectively control the reverse arch value and stress value of the capping beam within a reasonable range.

作者张海君邬晓光刘冉姚杰 ZHANG Haijun;WU Xiaoguang;LIU Ran;YAO Jie(Shanxi Provincial Transportation Planning Survey and Design Institute Co.,Ltd.,Taiyuan 030012,China;School of Highway,Chang'an University,Xi'an 710061,China)

机构地区山西省交通规划勘察设计院有限公司长安大学公路学院

出处《建筑结构》北大核心 2023年第S01期1742-1746,共5页 Building Structure

基金山西省交通运输厅科技项目(2021-1-2)

关键词桥梁工程既有旧桥主梁替换盖梁反拱值应力 bridge engineering existing old bridge main girder replacement cover beam reverse arch value stress

分类号 TU378 [建筑科学—结构工程]

作者简介第一作者:张海君,硕士,高级工程师,主要从事桥梁结构设计与分析研究,Email:413869162@qq.com。