Study On Nonlinear Finite Element Analysis Method Of Concrete-Filled Steel Tube Structure Under Cyclic Loading

Concrete-filled steel tube structure is widely used in the field of civil engineering,but the damage mechanism under earthquake is still not clear.In this paper,a finite element analysis method adapted to the nonlinear dynamic response of concrete-filled steel tube structure is studied.The main work of this paper includes:(1)Based on the Chaboche Combined hardening model,which simulated the mechanical behavior of steel under cyclic loading,the isotropic hardening parameter calibration equation was derived and extended,and the kinematic hardening parameter number rule and parameter solving formula were proposed.Based on the Chaboche model provided by Abaqus,the calibrated model parameters were used to simulate the cyclic loading test of steel,so as to verify the rationality of the parameter calibration method,and to study the influence of model parameters on the calculation accuracy of the mechanical response of steel members.(2)The finite element analysis model of concrete-filled steel tube structure is established by comprehensively applying the plasticity-damage model of concrete and the combined hardening model of steel.The simulation accuracy of the finite element model was analyzed by simulating the CFST column,CFST column-steel beam joint and CFST column-composite beam joint,and the influence of the interface bonding between CFST and steel tube on the simulation accuracy of the component response was studied.(3)The finite element analysis model of concrete-filled steel tube structure was constructed to simulate the nonlinear response of single-layer singlespan CFST column-steel beam plane frame structure,and the simulation effect of bondslip effect was analyzed.Through the above research work,the main conclusions of this paper include:(1)The parameter calibration method proposed in this paper for Chaboche model has high simulation accuracy.The model parameters determined by this method can ensure that the Chaboche model can well simulate mechanical phenomena such as Bauschinger effect,ratchetting effect,cyclic hardening with plastic shakedown under cyclic loading.The relative error range of the peak stress calculated by the selected experimental examples in this paper is-11.6%～8.5%,which can meet the requirements of engineering precision.(2)The finite element model established in this paper can simulate the nonlinear response of CFST structures.The results of failure mode,stiffness degradation,area of hysteretic loop,peak bearing capacity and peak displacement are in good agreement with the experimental results,and the relative errors of the calculated peak bearing capacity,peak displacement and peak hysteretic area are within 20%.At the same time,the bond-slip effect of steel-concrete interface has little influence on the calculation results.The sliding model was used to simulate the test specimen,and the ratio of the transverse and longitudinal slip amounts to the concrete diameter was less than 1/50.In order to improve the computational efficiency,the non-slip model is recommended to be used first.If higher calculation accuracy is needed,slip model can be used for analysis.(3)The non-slip model has the following shortcomings: first,the interface between steel tube and concrete is a common node,but the constitutive properties of the two materials are quite different,which may easily lead to the convergence problem;Second,the model ignores the bond-slip effect,and the stiffness simulation of the component is too large,leading to the calculated hysteretic curve is too full,and the hysteretic energy consumption is too large compared with the test results.In the example of the paper,the maximum error is up to 29%.