CFRP Strengthening Seismic Resistance Of Damaged Steel Reinforced Squat Shear Wall

In this study,five one-half scaled steel reinforced squat shear wall specimens were tested subjected to low-frequency cyclic loading regime to systematically investigate their seismic resisting behavior.These five specimens have identical reinforcement details,dimensions,and axial compressive ratio.The design variables include installing diagonal bracing,replacing buckling reinforcements,and different CFRP strengthening schemes.Based on the observation of the failure modes,the delamination of CFRP sheets,and measured load-displacement curves,the ultimate load resisting capacity,the degradation of load resistance and stiffness,the deformation capacity,the energy dissipation capacity,and deformation characteristic of the specimens are compared and evaluated.In addition,by comparing the predicted ultimate load resisting capacity from two analytical models with the measure ones,conclusions are drawn as below:(1)The load resistance of the five repaired specimens is similar and can be divided into four stages:elastic stage,the stage of CFRP delamination,yielded stage,and failure stage.These five specimens have bending deformation dominated bending-shear failure mode.(2)When repair the specimen,replacing the compressive buckling reinforcement at the bottom of the wall may not affect the ultimate load resisting capacity of the specimens.However,it could increase the yield load and initial stiffness of the specimens significantly.Moreover,replacing the compressive buckling reinforcement will improve the ductility and energy dissipation capacity of the specimens.(3)Repairing the diagonal bracing could increase the yield load capacity,ultimate load resisting capacity,ductility,and energy dissipation capacity of the specimens significantly.Moreover,it could mitigate the strength and stiffness degradation.(4)Both two CFRP strengthening schemes could recover the load resisting capacity,stiffness,ductility,and energy dissipation capacity of the specimens well and improve the strengthen and stiffness degradation.(5)Strengthening scheme A performed better than scheme B.Specimens repaired based on scheme A could recover their ultimate load resisting capacity over 90%.The strength and stiffness degradation of the repaired specimens with Scheme A is also better than that of corresponding original specimens.This indicates that X-shaped CFRP sheets could replace the function of diagonal reinforcing bracing partially.(6)In both two strengthening schemes,the horizontal CFRP strips could prevent the delamination of CFRP sheets effectively.(7)The predicted ultimate load resisting capacity from analytical methods,which are based on energy-based method and tie-and-strut models,has little difference compared with the measured results.Thus,the proposed two analytical models could be utilized to predict the ultimate load resisting capacity of seismic damaged steel reinforced squat shear walls.