高速铁路纵横梁体系结合桥面横梁面外弯曲问题的研究

Study on Horizontal Bending of Crossbeams of High-speed Railway Stringer-crossbeam Composite Floor System

中国大跨度高速铁路钢桁梁桥大多采用钢-混凝土结合桥面,横梁的面外弯曲是设计中的关键问题之一。本文针对高速铁路混凝土板仅与纵梁结合的纵横梁体系,从结合桥面系变形协调出发,推导出横梁面外弯曲问题的计算公式,并结合算例分析各种因素对横梁面外弯曲问题的影响。桥面系的连续长度和下弦杆的轴应力越大、下弦杆结点对于横梁的约束刚度越大、纵梁与下弦杆的距离越小,横梁的面外弯矩和弯曲应力越大。在四线铁路三主桁下承式钢桁梁桥中,中桁对横梁的约束近于绝对刚性,纵梁离中桁下弦杆的距离较小,使横梁的面外弯曲应力较二主桁桥梁大得多。

The steel-concrete composite floor system is widely used in large span high-speed railway truss bridges in China. Horizontal bending of crossbeams is a key issue in design. According to coordinated deformation of the floor system, the theoretical formulas of the horizontal bending of the crossbeams of the composite floor system where the concrete slab only combines with the stringers are deduced. In combination with numerical examples, the main factors influencing the horizontal bending of crossbeams are analyzed. The horizontal bending moment and bending stress of the crossbeams rise quickly with increasing of the constraint stiffness of the lower chord joint to the crossbeam, the axial stress of the low chords and the continuous length of the floor system and with decreasing of the distance between the stringer and the low chord. Constraint of the middle truss on the crossbeams approximates to absolute rigidity and the distance between the stringer and the middle low chord are small in the four-line through truss bridge with three main trusses, which produces much larger horizontal bending stresses of the crossbeams as compared with two-truss bridges.