Research On Seismic Behavior Of Rc Column Strengthened With Steel-Jacket Based On ABAQUS Fiber Beam Element

Fiber beam element has a high degree of fineness,and can simulate the hysteretic behavior of concrete members under the coupling of axial force and bending moment with considerable precision,so it is often used in seismic analysis of structures.General finite element program ABAQUS has powerful nonlinear solving ability,but limited by the application range of the built-in constitutive models,its built-in fiber beam element can not perform nonlinear seismic analysis of steel-concrete structure system well.In this paper,four hysteretic constitutive models were developed based on fiber beam element in ABAQUS,and were applied to the research on seismic behavior of steel-jacket strengthened columns and frames,which extends the application scope of fiber beam element,and provides the theoretical basis and efficient technical means for seismic simulation analysis and design of strengthened structures in practical engineering application.The main research works are as follows:(1)Based on user-defined subroutine UMAT in ABAQUS,a fiber beam element is developed for elastoplastic analysis of reinforced concrete structures and steel-concrete composite structures,including four hysteretic constitutive models of steel and concrete.The good convergence,high accuracy and efficiency of the developed element are proved through abundant calculation examples of low cyclic loading tests at home and abroad.(2)Based on the pseudo-static test results of steel-jacket strengthened columns,the fiber beam model for seismic performance analysis is established using the developed constitutive models,and the calculation from which are in good agreement with the test results in terms of bearing capacity and hysteretic performance.Then the parametric analysis of steel-jacket strengthened column is carried out by using the verified fiber beam model,the results of which indicate that: For strengthened columns subjected to tensile failure,the bearing capacity rises along with the growth of axial compression ratio,and the axial compression ratio of the original column is beneficial to the seismic performance,while the trend of those under compression failure is just the opposite.The increase of steel-jacket thickness will improve the seismic behavior.However,the earthquake damage of original column and the property of the filled concrete have no obvious effect on mechanical performance due to the effective confinement of steel-jacket.(3)The multi-scale models for structural seismic analysis are established based on fiber beam model and traditional finite element model.And the applicability and validity of the model,especially of the multi-scale interface connection,are verified through the pseudo-static test results of steel-jacket strengthened columns and a reinforced concrete frame.In addition,compared with the results of fiber beam model and traditional finite element model,the advantages of multi-scale model at the macro and micro levels can be demonstrated.Finally,the change of failure mode and the improvement of seismic performance of frame structure before and after strengthened are discussed by using the multi-scale model,and the modeling strategies and steps are also given in this paper.