Experimental Study And Numerical Simulation On Seismic Behavior Of Low-grade Reinforced Concrete Shear Wall Strengthened By ECC

In the earthquake,the collapsed buildings are the biggest threat to people.The collapsed building structures in the earthquake often have poor seismic performance,or the performance is reduced due to factors such as material aging and reinforcement corrosion after long-term use.The old structures that do not meet the current specifications or the buildings whose seismic performance does not meet the requirements after seismic evaluation need seismic reinforcement.As the main lateral force resisting member of the structure,reinforced concrete shear wall plays an important role in the process of resisting earthquake.The ductility and energy dissipation capacity of ordinary RC shear wall are low,and the longitudinal reinforcement buckling,rapid loss of bearing capacity and brittle failure often occur due to the concrete crushing of the foot under earthquake.Engineering cementitious composites(ECC)is a kind of cement-based material mixed with chopped fibers with a certain volume ratio.It has the characteristics of high ductility and strain hardening.Using ECC material for seismic reinforcement of shear wall can improve the crack resistance of the wall and improve the failure mode of the wall.At the same time,necessary structural measures are adopted to improve the restraint effect of the reinforcement layer on the wall,which can effectively delay the crushing and peeling of the concrete at the foot of the shear wall and improve the utilization rate of reinforcement.In this paper,three low-grade shear walls are designed to simulate the old or unqualified shear wall components.The two shear walls are strengthened with different forms of ECC,and the seismic performance is tested and numerically simulated.The main research contents are as follows:(1)PVA-ECC materials with various mix proportions were configured to make thin plate specimens and conduct uniaxial tensile test.The effects of water binder ratio,sand binder ratio,fly ash content and fiber volume ratio on the tensile properties of PVA-ECC were studied.(2)Three low-grade shear walls were made,and a common low-grade shear wall and two low-grade shear walls strengthened with different ECC strengthening forms were tested.The improvement in seismic performance of the strengthened wall in failure mode,hysteric curve,displacement ductility,stiffness degradation,energy dissipation capacity and so on was studied.(3)Based on OpenSees platform,two shear walls strengthened with different ECC strengthening forms are sheared with layered shell element.The simulation data are in good agreement with the experimental data.Based on the ECC reinforced shear wall with steel mesh,the parameter analysis is carried out to explore the influence of the thickness of the reinforced layer,the ratio of longitudinal reinforcement in the reinforced layer and the grade of the reinforced wall on the reinforcement effect.A 12 storey frame-shear wall structure is designed according to China’s specifications,and three overall equivalent models of ordinary RC frame-shear wall structure(RCFSW),ECC reinforced frame-shear wall structure(EFSW)and reinforced mesh ECC reinforced frame-shear wall structure(REFSW)are established by using Open Sees.The seismic vulnerability of the three structures is analyzed to explore the impact of different types of ground motions on the structure.