Seismic Performance And Evaluation Method Of Earthquake Resilient Shear Walls

The resilient seismic structure has become a new research direction in the field of seismic engineering.In recent years,it has been widely concerned by the global seismological engineering scholar and technicians.In the earthquake resistant structure,reinforced concrete shear wall is a kind of lateral force resisting component widely used in high-rise and super high-rise buildings,and it is the main aseismic defense line of the structure.The seismic performance of shear wall will greatly affect the seismic performance of the whole building.According to a large number of earthquake damage investigations,the traditional ductile shear wall structure designed based on seismic design codes has reduced the number of casualties and prevented collapses under large earthquakes,but it has caused serious economic losses,mainly due to the serious damage of buildings during the earthquake,which is difficult to repair after the earthquake and can only be demolished and rebuilt;or because of the need to repaire,but the repair time is long,the building function is interrupted,directly affecting people’s production and life.To solve the above problems,based on experiment in this paper,a new type of resilient reinforced concrete shear walls was put forward and its seismic performance was systematically studied.The main research contents are as follows:1)Four reinforced concrete shear walls were made by arranging PC strands as longitudinal reinforcements in the boundary elements of shear walls,two of which are ordinary reinforced concrete shear walls and two are resilient concrete shear walls,and a quasi-static test was carried out.Studies show that compared with ordinary reinforced concrete shear walls,the resilient concrete shear walls exhibit good drift-hardening capacity and have small residual deformation;a lack of energy dissipation,but their measured equivalent viscous dampings maintain almost constant along with the drift;it can effectively reduce its maximum crack width and corresponding residual crack width.2)In order to study the effect of axial load ratio and form of hoop in the boundary elements on the seismic performance of resilient concrete shear walls,as well as residual deformation and residual cracks,four full-scale reinforced concrete shear walls were fabricated.The quasi-static tests were carried out to study seismic performance of shear walls.The results show that the lateral deformation capacity decreases and the bearing capacity increases at the same displacement angle with the increase of axial load ratio,but the ultimate bearing capacity is not much different,and their Cumulative energy consumption and residual deformation are decreased and increased respectively.Compared with circular hoops in the boundary elements,the specimens with composite hoops have higher bearing capacity and lateral deformation capacity in a certain range,but they have no obvious effect on energy dissipation and residual deformation of resilient concrete shear walls.3)Two full-scale resilient concrete shear walls were fabricated.The effects of resilient concrete shear walls confined by CFRP in plastic hinge zone on failure modes,seismic performance,residual deformation and residual cracks were studied by pseudo-static test.The results indicate it can improve its bearing capacity and lateral deformation capacity,and it is better to improve its bearing capacity under high axial load ratio.After CFRP is wrapped in shear walls,the concrete in the plastic hinge zone is restrained effectively,which improves the lateral deformation capacity and bearing capacity of the specimens,effectively restrains the cracking of the concrete cracks and avoids the shear failure of shear walls.In addition,the energy dissipation capacity and residual deformation of the specimens were not significantly affected by CFRP wrapped in plastic hinge.4)ACI code and AIJ code equation are adopted to evaluate the flexural and capacities of the proposed walls,respectively.Among them,the bearing capacity of shear walls obtained by ACI code is in good agreement with the experimental results.Therefore,it is suggested that the combination of ACI code and AIJ code can be used to evaluate the failure modes of relisent concrete walls with PC strands in the boundary elements reasonably.Based on the results of pre-tests of resilient concrete walls,the characteristics of its skeleton curve are analyzed,and a simplified bi-linear skeleton curve model is proposed,and the calculation method of each characteristic point is given.This provides a reference for structural engineers in the preliminary design of resilient concrete walls.According to the damage status zone of post-earthquake buildings,the difference between ordinary reinforced concrete shear walls and resilient concrete shear walls is analyzed,and the repairability index of post-earthquake damaged resilient concrete shear walls is proposed based on the residual deformation,damage status and the difficulty of repair and reinforcement.5)Based on the repairability index of post-earthquake damaged resilient concrete shear walls,the method by confined steel plate is adopted to repair and reinforce it for the resilient concrete shear walls which have been seriously damaged,and the pseudo-static test was carried out to study the effect of repairing,seismic performance and restorability of the damaged relisent concrete shear walls strengthened by steel plate in plastic hinge region under different axial load ratio.The study found that the horizontal bearing capacity of shear walls after repairing can still keep increasing with the increase of lateral deformation,which indicates that shear walls after repairing with steel plate can be restored to the bearing capacity and deformation capacity under the earthquake,and the effect of reinforcement is better when the axial load ratio is higher.The residual deformation of the specimens can not be restored to the original state after repairing,but it only increases slightly accordingly.Therefore,shear walls after repairing still has a certain self-centering capacity.