Study On Seismic Performance Of RC Shear Wall Structure Reinforced With HRB600 High Strength Reinforcement

The use of high strength reinforcement is promoted for design of reinforced concrete(RC)structures in China.There are several potential benefits to the use of high strength reinforcement in RC buildings designed and constructed.These include steel savings,reduced energy consumption,reduction in carbon emission,and maintain sustainable development.Currently,test and analysis results for walls with high strength reinforcement are limited.In the present study,nonlinear analysis was performed for a building with conventional and high strength reinforcement;Deformation demand of shear wall was investigated;the effect of HRB600 bars on the seismic behavior of shear walls was tested;and the horizontal reinforcement stress level of HRB600 bars at peak load was discussed.The main research work and achievements are as follows:(1)Based on mechanical analysis of test results,a model for determining the shear stiffness of shear wall is developed.By compares the stiffness predicted by model analysis with test results,the predictions correlated well with test results.Furthermore,a formula,which is used to simulate the shear response of numerical model in Perform-3D program,is proposed.(2)Using Perform-3D finite element analysis software,the effects that high strength reinforcement on the seismic behavior of shear wall structures is studied through the analyses of the nonlinear dynamic response of buildings.The analyses results indicate that the dynamic response of features of structures with different strength reinforcement is similar;The top displacement,maximum drift ratio,shear force and strain level in the boundary of element is increased as the reinforcement strength increases;Conversely,inter-story drift stiffness and plastic energy dissipation are decreased as steel bar strength increases.In addition,the damage of shear wall members at bottom of structures is larger than that of the other regions.(3)Based on the numerical analysis,the maximum forced deformation for both SW400 and SW600 structures are happened at first story;The grade of steel bars has a small influence on the deformation in the region;By consider the influence of four uncertainly sources,when the maximum inter-story drift ratio of structures reached 1/120,the deformation demand limit value of shear wall members under 95% guaranteed ratio is 1/90.(4)A total of 15 RC shear walls(12 of them were reinforced with high strength reinforcement of HRB600 and the remaining 3 with normal grade reinforcement of HRB400)have been tested under cyclic loading.The test results reveal that failure mode of all the specimens is shear failure.The stress level of grade HRB600 reinforcement was less than the yield point,and the absolute stress of HRB600 horizontal bars was larger than that of HRB400 bars when the shear walls reaches peak load point.The walls with high strength reinforcement tend to achieve a larger ultimate deformation but slightly lower load carrying capacity.Both the initial stiffness and energy dissipation of the specimen hysteretic curves decrease as the reinforcement strength increases.The ultimate drift ratio for both “H” shaped and bar-bell shaped specimens with high aspect ratio was larger than the drift demand limit value(the value with 95% guarantee rate).When drift ratio of specimens reaches the demand value,the damage degree of “H” shaped specimens is severely than that of bar-bell shaped specimens,and specimens with high aspect ratio tend to lightly damages than the low aspect ratio specimens.Based on the concept of “drift ratio demand design”,peak shear strength equation provided by GB50010-2010 is evaluated using date from tests.Of the equation studied,the use of the GB50010-2010 equation could guarantee deformation capacity of rectangle shear walls to satisfy the deformation demand limit value.(5)Finite element models of shear wall members are constructed by VT2 program and used to parametric analysis(include: axial load ratio,web reinforcement ratio and concrete compressive strength)to study the effect of each parameter on the load carrying capacity of shear wall.Compared with the other two parameters,axial load ratio has more effect on the load carrying capacity of shear walls.The load carrying capacity is increased as the axial load ratio increase.When the ratio reached a certain value,the load carrying capacity is decreased as axial load increased.In the end,combined with the analysis results and previous test results,the limit value of tension strength of HRB600 shear reinforcement used in design code(GB50010-2010)are obtained.When the axial load ratio of design ranged from 0 to 0.4,the value of tension strength of HRB600 shear reinforcement decreased from 414 to 361 MPa.