钢管混凝土圆拱的面内承载力分析

迄今为止,全世界已有400多座钢管混凝土拱桥。然而,有关钢管混凝土拱面内承载力的设计规范仍没有。目前,钢管混凝土拱的设计广泛采用钢筋混凝土及预应力混凝土拱的面内承载力设计方法。这样钢管混凝土拱可认为受轴压或偏压作用,相当于钢管混凝土柱。将钢管混凝土柱的经典屈曲荷载作为钢管混凝土拱的参考弹性屈曲荷载。然而,在横向荷载作用下,钢管混凝土拱的面内弹性屈曲性能与轴压下的钢管混凝土柱完全不同,尤其是对于薄壁钢管混凝土拱。另外,与轴压或偏压下钢管混凝土柱不同,钢管混凝土拱在屈曲之前就发生非线性弯曲和横向变形,这严重影响钢管混凝土拱的承载力。因此,钢管混凝土面内承载力的设计方法是否正确值得商榷。提出与现有钢结构设计规范基本一致的钢管混凝土圆拱承载力设计方法,并同时考虑了几何非线性和材料非线性的影响。提出均匀轴压下钢管混凝土拱的面内承载力设计方程,及弯矩和轴压共同作用下钢管混凝土拱面内承载力验算的下限设计方程。

In-Plane Strength of Concrete-Filled Steel Tubular Circular Arches

More than 400 concrete-filled steel tubular(CFST) arch bridges have been constructed worldwide so far.However,design codes or guidance for the in-plane strength design of CFST arches are yet to be developed.In current design practice,the philosophy for the in-plane strength design of reinforced and prestressed concrete arches is widely adopted for CFST arches.For this,the CFST arches are considered under central or eccentric axial compression and are treated similarly to CFST columns,and the classical buckling load of CFST columns is used as the reference elastic buckling load of CFST arches.However,under transverse loading,the in-plane elastic buckling behaviour of CFST arches,particularly shallow CFST arches,is very different from that of CFST columns under axial compression.In addition,different from CFST columns under central or eccentric axial compression,CFST arches are subjected to significant nonlinear bending actions and transverse deformations prior to buckling and these will influence the strength of CFST arches greatly.Therefore,it is doubtful if the current method for in-plane strength design of CFST arches can provide correct strength predictions.In this paper,a method for the in-plane strength design of CFST circular arches,which is consistent with the current major design codes for steel structures,is developed by considering both geometric and material nonlinearities.A design equation for the in-plane strength capacity of CFST arches under uniform compression,and a lower-bound design equation for the in-plane strength check of CFST arches under combined actions of bending and compression are proposed.