| In order to achieve industrialization of buildings,countries around the world are committed to further research on prefabricated construction methods.The connection methods of the prefabricated beam-column joints mainly include wet connection and dry connection.The existing wet connection indicates that the seismic performance of the fabricated beam-column joints can be close to the cast-in-place by integral postcasting.However,existing wet connections mainly focus on the connection performance of the joints,but neglect the assembly process.The existing wet connection is usually post-casting in the core area of the joint,and the beam longitudinal rebar is anchored in the core area by 90°hook,so that the prefabricated beam cannot be installed after positioning the columns at both ends of the beam,so only one end column can be installed first;and the method will cause the core area to be crowded and difficult to be poured.To solute this problem,this paper proposes an improved integral post-casting beam-column joint.The beam-column connection is realized by double grouting sleeve,straight threaded sleeve and composite beam.The height of the core is same as composite beam to facilitate the overall post-casting of the beam and slab.The connection method of the beam-column joints can effectively realize the installation sequence of the prefabricated concrete structure like the steel structure,mounting column firstly,and then the beam and slab are installed.Under the support of Hubei Construction Science and Technology Plan Project(20171103)and Wuhan Urban and Rural Construction Committee Science and Technology Plan Project(201812),four double grouting sleeve connection prefabricated joints,two straight threaded sleeve connection prefabricated joints,one cast-in-place joint are manufactured The seismic performance of the fabricated concrete beam-column joints are studied by low cyclic loading tests.The main conclusions are as follows:(1)By comparing the specimen TJD-4 with the cast-in-place specimen XJ,it is found that the negative bearing capacity of TJD-4 is 8.9% larger than the negative bearing capacity of the XJ,and the forward bearing capacity of the XJ is 2.3%,indicating that the double grout sleeve connection can effectively transfer the load.(2)The hysteresis curves of the prefabricated nodes of the two connection forms are full,the energy dissipation coefficient E is between 1.1 and 1.36,the viscous damping coefficient ? is between 0.18 and 0.22,the strength and stiffness are degraded smoothly.The coefficient is between 0.93 and 0.99,and the ductility coefficient is between 4.48 and 5.66,and the ductility is good.(3)Due to the asymmetry of the connection method,the double grouting sleeve is used in the lower part of the beam,so it will affect the stiffness of the lower part of the beam to a certain extent.The most significant performance is that the negative stiffness is greater than the forward stiffness at the initial stage of loading.When the steel-sleeve has different degrees of bond-slip,it has different effects on the bearing capacity and hysteresis curve of the beam.The specific performance is that the negative bearing capacity is 64.6%~89.1% of the positive direction and fullness of hysteresis curves.(4)From the test results,there is no anchorage failure during the whole test.Therefore,it is feasible to use the hybrid anchor(beam longitudinal rebar anchored by head in the upper part of the joint and by the 90° hook in the lower part of the joint)in the prefabricated joint. |
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