Analysis Of Spatial Stability Of A Half Through CFST Arch Bridge

At present, most studies on the mechanical behavior and ultimate bearing capacity of CFST (Concrete-filled Steel Tube) arch bridge are focusing on geometrical nonlinearity, and the study about material nonlinearity has still been in initial stage. In addition, the stability studies are almost related to completed bridge or its service stage, the issues of construction stability haven't been studied deeply. For instance, the influence of temporary construction equipments such as guy-cable and suspending-fastening system, the influence of arch rib eccentricity caused by constriction error on structural stability have been considered less. In addition, there isn't qualitative and quantitative analysis about the beneficial influence of guy-cable on arch bridge stability under horizontal wind force. Based on these issues and current status quo of stability study, combined with two engineering projects, some researches are carried out as follows.1 Combined with the present stability analysis of CFST arch bridge in home and abroad, the foundational theories of ultimate bearing capacity taking into account geometrical nonlinearity, material nonlinearity and the double nonlinearity are summarized. And three representative theories of ultimate bearing capacity, the unified theory of CFST, the theory of fiber element model and the theory of three-dimensional nonlinear virtual laminated element, are introduced in detail. The unified theory is a semi-theoretical and semi-empirical formula, which substituts constitutive equation under axial compression for constitutive equation under eccentric compression, and needs to be perfected. The latter two theories are comparatively mature and can be used for engineering practice.2 On the project background of Rongzhou Bridge in Yibin acrossing Jinshajiang, a half through CFST arch bridge, its structural stability considering temporary equipments in construction stages is analyzed and the various factors which influence the stability coefficient are discussed. And theory of fiber element model is used to analyze and discuss geometrical nonlinearity, material nonlinearity and the double nonlinearity respectively which influence the stability of the arch bridge. The results suggest that the double nonlinearity must be considered in analyzing ultimate bearing capacity of CFST arch bridge.