斜拉桁架桥悬拼施工过程的力学行为分析

Analysis of Mechanical Behavior in Construction of Oblique-pulling Truss Bridge

为了保证斜拉桁架桥杆件悬臂拼装过程中结构的安全性,对其力学特性进行了分析研究。基于卡子湾大桥的三维有限元实体模型,计算了各施工阶段的结构线形、关键截面的应力及稳定特征值,并将结构竖向位移、杆件轴线偏位计算值、关键截面应力与现场测试值进行了对比分析。结果表明,结构实际刚度较大,使结构竖向位移测试值较计算值偏小;关键截面应力测试值与计算值的在整个施工过程中的变化趋势吻合较好,且结构从最大悬臂状态到全桥合龙阶段的结构受力状态是最不利的。从结构的稳定性来看,随着悬臂长度的增加,结构的面外稳定明显低于结构的面内稳定性,主要体现在部分桁架杆件的局部面外失稳。

Cantilever installation is a commonly used method of construction in the superstructure construction of oblique-pulling truss bridge. For considering construction safety, the mechanical behavior was analyzed for each phase of superstructure construction of the bridge. Based on building 3-D finite-element model of Kaziwan Bridge, girder＇ s alignment, key section＇s stress and stability of the different construction phases were calculated, and the comparative analysis between the calculation results and the test＇ s results on vertical displacement, axis deviation, key section＇s stress was carried out. The results show that （1） the measured values of vertical displacement are smaller than the calculation values due to actual stiffness of structure is larger than theory stiffness; （2） change rules between the theoretical calculation and the measurement value of key section＇ s stress of the bridge agree pretty well in the construction, and structural mechanical behavior is the most disadvantageous from the maximal cantilever length phase to entire bridge closure phase; （3） the outward direction stability is obviously poor than the inward direction stability with cantilever length increasing and local outward loss stability is quite obvious on partial truss members.