Sectional Hysteretic Model Of Concrete-filled Circular Steel Tubes

Definite resilience model is the basis of the structure of Pushover analysis. The internal force of the arch bridge is a stable axial force, so it is suitable to use the resilience model based on the section. But looking up present research status, most researches about resilience model of concrete-filled steel tube(CFST) beam-columns are under the horizontal unidirectional cyclic loading with constant axial force, which didn’t hang together with the stress performance of the CFST arch bridge under the seismic excitation of transverse, whose axial force and in-plane bending moment is not obvious with huge changes on out-plane bending moment. In this paper finite element analysis of CFST would be carries out, and put forward moment-curvature restoring force model of circular CFST bi-axial bending and compression after regression analysis.First of all, in order to get the changes of internal force on arch rib section under the seismic excitation of transverse, finite-element simulation is used for analysis of CFST arch bridge. The results show that the direct stress of the Arch rib section changes little under the combined load of axial force and in-plane bending moment, whose maximum change rate is 16.87% under the seismic excitation of 600 gal. But the out-plane bending moment changes significantly, whose maximal change rate is 46.78%. This results are close to people’s cognizance of the CFST arch bridge’s stress performance under seismic excitation of transverse.Secondly, according to the realistic conditions of experiment results in literature cite, make the finite element modeling of 8 groups of concrete-filled circular steel tube and get models’ load-displacement hysteretic curves after calculation. After comparing the calculation results with experiment results, it’s easy to find that the simulating results agree very well with the experimental data which verifies the reliability of this model in this paper.And then, make the uniform designs with multifactor and multilevel of 5 parameters,such as nominal steel ratio, axial compression ratio, in-plane bending moment ratio, average compressive strength of concrete cubes, tensile strength of steel, which will have a greater impact on circular CFST’s hysteretic behavior. Afterwards, prepare 16 groups of numerical simulation experiment, and extract moment-curvature hysteretic curves after making calculations with the verified finite element modeling. Besides, this thesis makes an explanation of circular CFST’s whole process of bearing capacity with bi-axial bending and compression states.Finally, using SPSS software performs regression analysis of characteristic points of each hysteretic curve. And propose a Three-Line resilience model of circular CFST with bi-axial bending and compression. Perform moment-curvature recalculations with Three-Line resilience model and make comparisons between Three-Line resilience model’s results and finite element simulation’s results. Well dovetail has verified the veracity of regressed resilience model.