Experimental Study On Seismic Performance Of Precast Shear Wall Considering Defects In Sleeve Grouting Connection

As an important direction for architecture industrialization in China,prefabricated building has the advantages of reliable manufacture quality,high standardization and fast construction speed.Grouted sleeve connection is one major connection means of assembled concrete members,and the connection performance is affected by grouting quality.However,there is no authorized way so far to detect the defect,and it is difficult to evaluate the on-site grouting quality.In addition,there are few studies on the effect of grouting defects on the performance of assembled structures.These factors prevent the wide application of sleeve grouting connection technology in assembled concrete structures.Based on the present situation,precast shear wall with sleeve grouting connection is chosen as the research object,and the effect of grouting defects on the performance of sleeve connectors and assembled shear wall specimens are discussed.The effectiveness of non-destructive testing method for grouting defects is also discussed.The main work of this dissertation is summarized as follows:(1)Based on the most common grouting defects in practical engineering,42 reinforcement sleeve connectors were designed and manufactured for unidirectional tension test in order to investigate the failure characteristics of sleeve with different grouting defects.Defect types include uniform distribution defects,end defects,anchorage length defects and central defects.The results show that central defects and uniform distribution defects have greater influence on mechanical behaviors than end defects and anchorage length defects when the dimension of defects is same.Eccentricity defect has insignificant influence on the connection performance of specimens.For horizontal defects,when the dimension reaches 6mm,the failure mode of specimens may become pulling-out of bar.(2)In this study,X-ray is adopted to identify the interface between steel sleeve and grouting material as well as the interface between grouting material and steel bar.It is easy to identify the defect through the darkest area of the slice image.For the sleeve connectors designed in this experiment,the accuracy of X-ray detection is more than 1mm with YXLON micro-focus X-ray computed tomography system.(3)In order to study the effect of grouting defects on the performance of precast shear wall,four specimens were designed and tested under cyclic loading,and three of them had different grouting defects.The results show that grouting defects will lead to the excessive opening gap between the bottom of the wall and the beams during the loading,and eventually lead to the failure mode of pulling-out of bars at defected positions.Grouting defects have insignificant influence on the cracking load of specimens,while they will reduce the yield load of specimens.Besides,grouting defects will reduce the peak bearing capacity as well as the failure under a small displacement.The stiffness of specimens with grouting defect is slightly less than that of full grouting specimens when the displacement is larger,and the energy dissipation capacity is also relatively reduced.(4)Numerical model of precast shear wall is developed by using the OpenSees finite element software,including the simplified simulation of mechanical behavior of grouting defeat.The results math well with the experimental results,which shows the feasibility of the simulation method.However,the simulation of specimen with grouting defects should be further investigated in future study.