In-plane Stability Of FRP Confined Concrete-filled Steel Tubular Arches

Due to high bearing capacity,construction convenience,and good seismic behaviors,concrete-filled steel tubular(CFST)arches have been widely used in bridge structures.However,in coastal areas,saline-alkali areas,and cold regions where deicing salts are frequently used,the corrosion problem of the outer steel tube in CFST is becoming more serious,which can affect the structure performance,decrease the durability of arch bridges,and even lead to certain safety hazards.Meanwhile,high maintenance cost is required to deal with corrosion problems during the construction and operation processes.In order to solve this problem,a structural form of FRP-confined concrete-filled steel tubular arch is proposed in this dissertation.The experimental studies and finite element analysis of such arch structures are carried out.The main research work is as follows:(1)Axial compression tests on 2 CFST columns and 10 FRP-confined CFST columns with different FRP thicknesses and FRP winding patterns are conducted.The test results show that the FRP wrap can effectively delay or completely avoid the local buckling of outer steel tubes,and can significantly improve the ultimate bearing capacity and corresponding axial deformation of specimens.Besides,the influence of the FRP winding angle on the capacity of FRP-confined CFST columns is analyzed by a test-verified finite element model.Based on the analysis results,the calculation equation of the axial bearing capacity of FRP-confined CFST stub columns is proposed,which takes into account the effect of FRP winding angle.(2)The fabrication and in-plane stability tests of 5 FRP-confined CFST parabolic arches and 1 CFST parabolic arch under the mid-span load are conducted.The effects of rise-to-span ratio and FRP winding patterns on the bearing capacity are investigated.The test results show that the specimen is mainly bearing bending moment under the mid-span load,and the in-plane stability capacity increases with the increase of rise-to-span ratio and longitudinal winding FRP layers.(3)The stability behaviors of FRP-confined CFST parabolic arches under the mid-span load and uniformly distributed loads are investigated using the ABAQUS finite element model,which is verified by test results.Besides,the effects of FRP thickness,steel ratio,slenderness ratio,and rise-to-span ratio on the stability capacity are analyzed.Furthermore,on the basis of finite element results and existing calculation equations of in-plane stability capacity of CFST arches,the in-plane stability design methods for FRP-confined CFST arches under uniformly distributed loads and the mid-span load are both proposed.(4)Two damaged arches are reinforced by FRP wraps,and the in-plane stability tests of these two specimens under the mid-span load are conducted.The test results show that the specimen stiffness after effective FRP reinforcement is lower than that of arches under the initial loading,but the bearing capacity and deformation stay similar.The engineering proposal for reinforcing CFST arches with FRP wraps is provided based on the test results.