Experimental Study On Seismic Performance Of Local Replacement Shear Wall

In order to protect natural resources,high-rise buildings are widely used.In high-rise buildings,reinforced concrete shear wall structures are the most widely used structural form due to their excellent integrity and seismic resistance.In actual engineering construction,due to various reasons,the concrete strength of shear walls is low,does not meet design requirements,and there are often quality defects.In addition,due to the different requirements for seismic fortification intensity in different eras,the fortification intensity during building renovation is higher than the original design.The above situations will cause the shear wall to not meet the seismic requirements and require reinforcement treatment.Therefore,the study of seismic reinforcement methods for shear walls has certain practical significance.This article first summarizes the common reinforcement methods for shear walls,analyzes the advantages and disadvantages of various reinforcement methods,and proposes a local replacement concrete reinforcement method to address the low quality defect of shear wall concrete strength.This article designed a total of 12 shear wall specimens,including 3 specimens with a measured concrete strength grade of C35,and the other 9 specimens with a measured concrete strength grade of C15.Among the 9 specimens with a concrete strength grade of C15,3specimens were partially replaced at both ends by 200 mm,3 specimens were partially replaced at both ends by 300 mm,and 3 specimens were not replaced.The measured strength grade of the replaced concrete was C45.The seismic performance of local replacement shear walls was studied through quasi-static tests,with a focus on the stress mechanism,failure mode,bearing capacity,and the influence of axial compression ratio and replacement range on the seismic performance of shear walls under earthquake action.The following main conclusions were drawn through experimental research and theoretical analysis:(1)The failure process and morphology of the specimens reinforced with local displacement at both ends under horizontal seismic loads are basically similar to those of the unreinforced specimens.Eventually,the tensile steel bars yield,the concrete in the compression area is crushed,the compression steel bars buckle,and normal section failure occurs.The component reaches its ultimate bearing capacity without shear failure.The local displacement concrete is well combined with the original concrete.(2)For specimens with lower concrete strength,as well as specimens with lower concrete strength that use local displacement at both ends but smaller displacement area,when the axial compression ratio is high and the ultimate lateral bearing capacity is reached,the effective cross-sectional area of the component decreases due to the crushing and detachment of concrete in the compression area at both ends under reciprocating loads,which is insufficient to bear vertical loads.The entire component will undergo sudden failure similar to axial compression,and the component will completely lose its bearing capacity,Therefore,when using local replacement to reinforce shear walls,a reasonable replacement range should be determined to avoid such damage.(3)After using high-strength concrete to locally replace and reinforce the end of the shear wall,the lateral bearing capacity of the specimen will be improved.When a certain local replacement length is met,the lateral bearing capacity of the component is mainly related to the concrete strength of the material used for replacement.The increase in lateral resistance of the component after partial replacement reinforcement is related to the strength grade and replacement area of the concrete before and after replacement.The greater the increase in strength grade of the replacement concrete compared to the concrete before replacement,the greater the increase in lateral bearing capacity of the specimen.The larger the local displacement area,the higher the lateral bearing capacity.However,if the replacement length exceeds the height of the compression zone when the ultimate bearing capacity is reached,the increase in local replacement area has little effect on the lateral bearing capacity of the component.(4)When the axial compression ratio is large,the ductility coefficient of the specimen is small.When the concrete strength of the specimen is low,the axial compression ratio is large,and its ductility is also significantly reduced.After partial displacement at the end,the ductility of the component can be improved when the axial compression ratio of the specimen is not greater than 0.5;For specimens with large axial compression ratios,if the local displacement area is large,the ductility after displacement will also be improved.However,if the displacement area is small,the ductility of the specimen cannot be improved.