Experimental Study On Fully Precast Concrete Shear Walls With Grouted Butt Joints

In this paper,a reinforcement butt connection method based on corrugated pipe grout anchor is proposed and applied to the fully prefabricated shear wall.In other words,the metal corrugated pipe is used to reserve the channel in the wall.The outer ring of the channel is added with help bars and spiral stirrups.The connecting steel bar is upset and docked in the channel by grouting.Finally,the upper and lower shear walls are connected together.Being different from grouting sleeve,the use of upsetting steel bar can reduce the length of anchorage,thereby saving materials.Using metal bellows to reserve holes,steel deviation space is large and easy to install,additional bars can ensure the continuous force transmission,the ductility of joints can be improved by using spiral stirrups.6 prefabricated and 3 cast-in-place shear wall specimens were investigated by quasi-static test.The influence of vertical distribution steel connection mode,height-width ratio and axial compression ratio on seismic performance was explored.For the prefabricated specimens with bottom failure,the parametric analysis was carried out based on finite element method,and the recommended axial compression ratio and height-width ratio were given.For the prefabricated specimens with central failure,the structural optimization scheme was discussed based on finite element method.On this basis,the quasi-static test was carried out on 2 structural optimization specimens and 2 cast-in-place specimens,and the feasibility of the optimization scheme was verified.The main conclusions of this paper are as follows :(1)The quasi-static test of shear walls connected with grouted butt jointsAll specimens show flexural-shear failure modes of concrete crushing and vertical steel bar breaking,and 1/2 of the fabricated specimens are damaged at the bottom of the wall,compared with the cast-in-situ specimens,the bearing capacity of the fabricated specimens is significantly improved,the stiffness and displacement ductility are close,and the energy dissipation performance is slightly reduced,which can achieve the seismic performance requirements of “equivalent to cast-in-situ”.The failure of 1/2 prefabricated specimens is located above the grout-anchor joint of the edge member,compared with the cast-in-situ specimens,the stiffness is close,the bearing capacity,displacement ductility and energy dissipation performance are slightly reduced,and the seismic performance is weakened.With the increase of axial compression ratio,the bearing capacity of the fabricated specimens is significantly improved,the equivalent stiffness increases,and the displacement ductility and energy dissipation performance decrease.There is no bond-slip phenomenon in the grouted anchor bars of the fabricated specimens with one-by-one connection and plumshaped connection in the distribution area.The connection ways of distribution bars have no significant effect on the mechanical properties of the horizontal connection joints.(2)Parametric analysis and structural optimization based on finite element methodThe skeleton curve of finite element simulation has a good envelope to the test hysteresis curve,and the bearing capacity error is less than ± 5%.The damage nephogram can accurately reflect the failure mode of the specimen,and the finite element results are accurate and reliable.On this basis,the parametric analysis of the shear wall with bottom failure is carried out,it is suggested that the axial compression ratio should not exceed 0.4,and the height-width ratio should be in the range of 1.5-2.5.Four structural optimization schemes are proposed for the shear wall with middle failure and the finite element modeling analysis is carried out,the results show that the stress concentration at the top of the joint can be effectively improved by adjusting the height of the outermost two rows of joints of the edge member according to the10 d range.Considering the convenience of construction,it is suggested that only the height of additional reinforcement and spiral bars in the joint should be adjusted.(3)The quasi-static test of shear walls after structural optimizationThe failure mode of the specimens after structural optimization is equivalent to that of the cast-in-situ specimens.Compared with the prefabricated specimens with middle failure,the bearing capacity and displacement ductility are significantly improved,the stiffness is close,and the energy consumption is more sufficient.The structural optimization scheme is reasonable and effective.The differential adjustment of joint height improves the stress concentration in the middle of the wall,and effectively improves the seismic performance of the specimen while changing the unfavorable failure mode of the fabricated specimen.