某T形刚构桥施工过程病害维修方案设计

Design of Maintenance Schemes for Deterioration Developing in Construction Process of a T-Shaped Rigid-Frame Bridge

某T形刚构桥在顶板预应力张拉过程中出现了箱内顶板混凝土崩裂病害,病害原因为混凝土强度不足和预应力定位偏差。针对该病害,提出顶板局部凿除方案(凿除崩裂区顶板,顺直管道后恢复)和顶板局部补强方案(新增横隔板),采用MIDAS建立该桥有限元模型,从施工难度和结构应力两方面进行比较分析,最后确定采用施工难度小、顶板压应力均匀且极值较小的局部补强方案作为推荐方案。采用减少预应力和增加铺装层厚度对推荐方案进行结构应力和主梁线形的优化,并对优化后维修方案进行施工阶段和成桥状态的结构验算。结果表明:结构各项验算指标均能满足规范要求,证明维修方案是合理的,通过维修可以保证桥梁的施工过程安全及使用要求。

T he deterioration of top plate concrete cracking occurred inside the box girder of a T‐shaped rigid‐frame bridge during the tensioning of the top plate prestressing tendons ,which was attributed to deficient concrete strength and prestress positioning deviation .In light of this deterio‐ration ,two schemes are proposed ,one is to locally remove the top plate ,that is ,to remove the cracked top plate and recast it after the prestressing ducts are straightened ;and the other is a local strengthening method ,namely to add diaphragms .MIDAS was used to establish the finite element model of the bridge to compare and analyze the two schemes from aspects of construction complexi‐ty and structural stress .As a result ,the local strengthening scheme which features low construc‐tion complexity ,uniform top plate compressive stress and smaller threshold value of compressive stress was determined as the recommended scheme .The recommended scheme was optimized in terms of structural stress and main girder geometry by reducing prestressing tendons and increas‐ing the thickness of deck pavement ,and the structure of the bridge during the construction process and in the completed bridge state was checked after the maintenance scheme was optimized .The results of the checking demonstrate that all the checking indexes of the structure could meet the code requirements ,proving that the maintenance scheme is rational .T he maintenance ensures that the bridge construction process is safe and its service condition meets the requirements .