Study On Failure Characteristics And Finite Element Method Of Wide-Limb Reinforced Concrete Frame With Special-Shaped Columns

Compared with rectangular columns,reinforced concrete special-shaped columns can effectively avoid indoor column edges and corners,increase the use space and improve the house appearance,and the RC special-shaped column frame structure system has strong seismic performance when applied to multi-storey buildings.The promulgation of the new technical specification for RC special-shaped column structure in 2017 and the notice on strengthening green and low-carbon construction in the county(Exposure Draft)in 2021 provide policy support for the further application of this system in multi-storey buildings.Through practical research,it is found that it still has weak parts such as the first floor column bottom and beam column joints under earthquake,which seriously limits the floor height.In this paper,the wide limb special-shaped column is taken as the research measure to improve the seismic performance of ordinary RC special-shaped column frame,Based on the existing tests,the influence of different parameters on the seismic performance of special-shaped column structure is studied by finite element method.The specific research work is as follows:Based on the test of RC wide limb special-shaped column frame,the finite element modeling and analysis method it are analyzed,and the mechanical performance under reciprocating load is studied.The reliability and rationality are verified by comparing the hysteretic curve,skeleton curve and bearing capacity of the test and model.By changing the axial compression ratio,limb height to limb thickness ratio and concrete strength,15 wide limb special-shaped column models are designed for finite element expansion research.Through the comparative analysis of their hysteretic curves and skeleton curves,it is obtained that the bearing capacity,displacement ductility,stiffness degradation and energy dissipation capacity are the evaluation indicators of seismic performance.The results show that the ultimate bearing capacity and deformation capacity decrease gradually with the increase of axial compression ratio.After the axial compression ratio exceeds 0.2668,the finite element model calculation can not pass and make the structure fail;Increasing the ratio of limb height to limb thickness can increase the ultimate load and energy dissipation coefficient,which can improve the energy dissipation capacity and seismic performance of the frame structure.The seismic performance of the model with the ratio of limb height to limb thickness of 4.25 is the best;Increase the concrete strength,reduce the yield displacement,increase the bearing capacity,enhance the energy dissipation capacity of members,and improve the seismic performance.In order to compare the effect of wide limb improving the seismic performance of special-shaped column frame,based on the above finite element research,this paper compares the seismic characteristics and finite element analysis of an ordinary specialshaped column frame,and studies the mechanical performance of ordinary special-shaped column frame under reciprocating load.The comparative study shows that the wide leg can effectively improve the failure characteristics and seismic characteristics of ordinary concrete special-shaped column frame,and puts forward a solution to improve the floor height of special-shaped column frame building.At the same time,by changing the axial compression ratio,concrete strength and column reinforcement diameter of ordinary concrete special-shaped column frame,14 special-shaped column frame models are designed for finite element analysis.Through the comparative analysis of their hysteretic curves and skeleton curves,the seismic performance evaluation indexes such as bearing capacity,displacement ductility,stiffness degradation and energy dissipation capacity are compared.Finally,based on the numerical simulation of finite element model,the restoring force model of wide limb special-shaped column frame structure with axial compression ratio,limb height to limb thickness ratio and concrete strength is established.The three broken line skeleton model is established by linear regression fitting method,and the correctness of the model is verified by experimental data,The model can effectively reflect the load displacement variation law of wide limb special-shaped column frame structure under low cyclic reciprocating load.The model has certain applicability,lays a foundation for the study of seismic performance of the structure,and also has certain reference value for practical engineering.