Seismic Collapse Analysis Of Reinforced Concrete Frame Structure With Damage Degradation And Strain Rate Effect

In China,the RC(reinforced concrete)frame structure is the most widely used in the building structure.During use,it is inevitable to suffer from seismic loads,and the impact of serious damage to the building or even collapse subjected to severe earthquake will cause a lot of casualties and economic losses.Therefore,it is necessary to study the development process of the collapse of reinforced concrete frame structure and explore its causes.In this paper,the material subroutines are coded based on the ABAQUS and the numerical simulation of the collapse process of a RC frame structure is conducted by using the subroutines.The collapse mechanism of the structure is analyzed,and the research ideas and analysis methods of structural damage are proposed.The primary contents are listed as follows:(1)Based on the ABAQUS explicit dynamic module,the subroutine of materials considering strength and stiffness degradation caused by cumulative damage and strain rate effect is developed for collapse analysis.The comparison between the simulated results and experimental results of a RC column under static and dynamic loading modes proves the reliability of the coded subroutine.(2)The finite element model of plane frame is established by using fiber-beam element to simulate the pseudo-static collapse experiment of one 3-layer-3-span RC frame which was completed by Tsinghua University.The simulation results are consistent with the experimental results published by Tsinghua University,which means that the finite element model based on the fiber-beam element can simulate the nonlinear reaction of the RC frame structure well.It also proves that the developed subroutine can simulate the pinch and degradation characteristics of RC Frame Structure.(3)The structural response under different loading modes of a six-story RC frame is analyzed by the pushover capacity spectrum method,the target performance points of the structure are determined respectively to evaluate the performance of the structure,and the influence of the weak layer reinforcement on the structural performance is studied.The results show that different loading modes reflect different structural inertial forces distribution,which leads to different analysis results;the seismic performance of the structure can be improved to a certain degree by strengthening the structural reinforcement of the weak layer.(4)Incremental dynamic analysis of a six-story RC frame structure is conducted to study the dynamic response of the structure during the seismic collapse process.The results show that the load-bearing capacity of the structure is improved when the strain rate effect is considered,but the degradation effect is more obvious.Therefore,the structural analysis under the earthquake should take the rate effect and degradation effect into account.By defining the component damage and layer damage,the numerical simulation can monitor structural damage,give the weak layer and the failure path,reveal the collapse mechanism of the structure and provide reference for the anti-collapse design.