In-plane Stability Of Parabolic Concrete-filled Steel Tubular Truss Arches

In recent years, concrete-filled steel tubular(CFST) arches have gained a vast development in China, leading to an increasing number of CFST arches built in recent twenty years. According to incomplete statistics, there are more than 300 arch bridges using CFST as their structural members, and more than 50% arch ribs are truss section. CFST truss arches are widely used in long span bridges due to their favorable spanning ability and appearance, and the longest span for this type of bridge has reached 500 m. Compared with the rapid development, the investigations on CFST truss arches are quite limited. Most of the researches are focusing on a particular arch bridge, rather than developing design method. In this dissertation, the parabolic truss arches which are widely used are selected, and the in-plane stability of this type of arch is investigated. The specific research work is as follows:(1) Finite element modeling and verificationThe FE model of CFST truss arches are built by using ABAQUS. A comparison analysis is conducted to select the appropriate element type and a nalysis method. Both the geometrical and material nonlinearities are included in the model. Typical calculation parameters and cross sections are selected according the technical code for CFST arch bridges(GB50923-2013) and practical bridges. The test results on CFST parabolic arches and CFST lattice columns are selected to verify the FE model. The comparison shows that the FE model can be used to simulate the CFST truss arches.(2) In-plane stability of CFST parabolic truss arches under axial compressionThe equivalent ratios of three types of cross sections which are commonly used in truss arches are derived by considering the shear deformation of the trusses. Based on this, the in-plane buckling behaviors of CFST parabolic truss arches are analyzed. In addition, the influences of slenderness, rise-span ratio and cross section on the buckling behaviors of CFST parabolic truss arches are investigated. Through the comparison between FE results and test results, it is known that the calculation equation proposed in this work could accurately predict the in plane strength of CFST parabolic truss arches under axial compression.(3) In-plane stability of CFST parabolic truss arches under combined axial compression and bending.The internal force distribution rules are obtained through first order elastic analysis of CFST parabolic truss arches. In addition, the influence of rise-span ratio and geometrical imperfection on the in-plane strength of CFST parabolic truss arches under combined axial compression and bending is also investigated. Based on the investigation, a design equation is proposed and verified by the FE results. The comparison between the verified results and the FE results shows that the equation proposed in this work could well predict the in-plane strength of CFST parabolic truss arches under combined axial compression and bending.