轨道交通U形梁底板横向抗裂及预应力布置研究

针对目前轨道交通U形梁底板横向仅布置普通钢筋的构造特点,为了提高轨道交通U形梁底板横向抗裂性能和安全性能,以青岛地区某无砟轨道交通U形梁为研究对象,采用有限元仿真分析方法,研究U形梁底板横向抗裂和应力分布,并提出一种横向预应力布置方式。研究结果表明:跨中底板的横向拉应力主要由自重和设计荷载引起,而梁端底板的横向拉应力则受纵向预应力、自重等多因素影响。设计荷载作用下,结构最大横向拉应力为1.71 MPa;在1.3倍超载作用下,最大横向拉应力达到2.04 MPa,超过规范要求,结构安全储备较低,横向抗裂性能较弱。布置横向预应力后, U形梁跨中底板底面横向拉应力明显减小,达到-0.117 MPa,且拉应力的分布趋于均匀,结构安全性显著提高。研究结果可为U形梁底板抗裂及横向配筋设计提供借鉴。

Transverse anti-cracking of bottom slab and layout of transverse pre-stressed tendon of rail transit U-shaped girder

Rail transit U-shaped girder had the structural characteristic of only arranging ordinary regular reinforcements in transverse direction of bottom slab. Based on a rail transit U-shaped girder project in Qingdao, in order to improve its safety and transverse anti-cracking performance, finite element analysis method was used to study the transverse anti-cracking and stress distribution of bottom slab of U-shaped girder. An arrangement method of U-shaped girder transverse pre-stressed tendons was put forward. The results showed that, the transverse tensile stress of bottom slab of midspan was mainly caused by self-weight and design load, while transverse tensile stress of girder ends was influenced by many factors. Under design load, maximum transverse stress of structure was 1.71 MPa, while applying 1.3 times overloading, maximum transverse stress reached 2.04 MPa, which was beyond code requirements. Safety margin of U-shaped girder was low and transverse crack resistance was weak. The proposed layout of transverse pre-stressed tendons effectively decreased transverse tensile stress in bottom slab of girder midspan to -0.117 MPa. The distribution of tensile stress became more uniform and structural safety was significantly improved. The research could provide a reference for transverse reinforcement design of U-shaped girder bottom slab.