High Efficient Simulation Method And Application Of RC Frame Structures Considering Reinforcement Slip Effect

Experimental results of structural seismic show that the deformation of reinforced concrete(RC)frame members caused by the reinforcement slip effect under earthquakes can account for more than 30% of the total deformation.For members with low axial compression ratio,this deformation is approximately equivalent to flexural deformation.Therefore,this reinforcement slip effect cannot be ignored in the finite element analysis for seismic performance of RC frame structures.The traditional finite element analysis for seismic performance of RC structures to simulate the reinforcement slip effect requires the addition of elements(spring element and zero-length section element,etc.),which often results in too many elements,time-consuming numerical analysis,nonconvergence of numerical solutions,and tedious modeling.This paper proposes a fiber model considering reinforcement slip effect,thereby presenting a high-efficient simulation method that can simulate the reinforcement slip effect in RC members.Moreover,the effect of reinforcement slip on the seismic capacity of RC frame structures is investigated.The main contents and results of this research work are listed as follows:(1)In this paper,assuming that the reinforcement slip effect in RC members is equivalent to the steel bar strain,a calculation formula for steel bar strain considering reinforcement slip effect is established.And a bilinear stress-strain constitutive model of steel bar considering reinforcement slip effect is proposed.The model can consider the effect of many parameters on the reinforcement slip in RC members,including compressive strength of concrete,diameter of steel bar,yield strength of steel bar,and section height of member.Then a fiber model considering reinforcement slip effect is proposed.Therefore,a high-efficient simulation method of seismic analysis based on the proposed fiber model is established to consider the reinforcement slip effect in RC structures.(2)Based on the selected 48 RC columns with different design parameters,the multilevel test data are used to verify the proposed fiber model considering reinforcement slip effect(proposed fiber model).Moreover,the numerical results from the traditional fiber model and the existing zero-length fiber model considering reinforcement slip effect are used as auxiliary verification.The performance evaluation of the proposed fiber model and zero-length fiber model is performed by comparison results of 48 RC columns,and the sensitivity of different design parameters in RC members to the performance of the proposed fiber model is further analyzed.The results show that the accuracy and reliability of the proposed fiber model are validated at the member and section levels.The average values of the pushover coefficient,stiffness ratio,moment ratio,and degradation coefficient in the proposed fiber model are 0.129,1.256,0.991,and 16.456,respectively,while that of the zero-length fiber model are 0.134,1.085,0.986,and 11.295,respectively.(3)A typical RC frame structure is designed,and based on the proposed and traditional fiber model,4 frame finite element models are established.The effects of reinforcement slip in frame beams and columns on the seismic capacity of structure are investigated.The results show that compared with the reinforcement slip in frame beams,the reinforcement slip in frame columns has a more significant influence on the seismic performance of frame structure.Under rare earthquake,the reinforcement slip in frame columns can cause an increase of maximum drift ratio by about 40.9%.Therefore,when performing deformation check under rare earthquakes for RC frame structures,it is recommended that the reinforcement slip in members should be considered,at least the reinforcement slip in frame columns should be considered.(4)9 RC frame structures are further designed,and based on the proposed and traditional fiber model,18 frame finite element models are established.Then,the effect of reinforcement slip in RC frame columns on the seismic performance of structure with different structural design parameters is investigated,including structure fortification intensity,structure layer,and structure aspect ratio.The results show that the effect of reinforcement slip in frame columns on the maximum drift ratio gradually increases with the increase of the structure fortification intensity,and gradually decreases with the increase of the number of structure layer,and gradually decreases with the increase of the structure aspect ratio.