| As the country pays more and more attention to the green and ecological sustainable development,precast prefabricated structure should be born in response to the situation.The low energy consumption and low pollution,construction speed block,fine quality control and other advantages of precast prefabricated structure are more and more favored by everyone.Among them,prefabricated reinforced concrete frame structure is a widely used structural system.The connection between beam and column directly determines the overall mechanical properties of the structure.It is the focus of seismic research and the premise and foundation of the overall seismic performance of the structure.Based on the research of a large number of scholars,this paper presents a new beam-to-column joint of precast RC frame,which connects prefabricated beam and prefabricated column through embedded section steel by butt welding of steel plate.Through experimental study and numerical simulation,the hysteretic curve,skeleton curve,bearing capacity,stiffness,ductility and energy dissipation of the joint are studied.The influence of different parameters on the seismic performance of the new beam-column joint is analyzed.According to the results of experiment and numerical simulation and the characteristics of the new prefabricated beam-column joint,the design method and construction requirements of the new prefabricated beam-column joint are put forward.The main conclusions and innovative achievements are as follows:(1)The seismic performance of the new beam-column joint of precast RC frame is comparable to that of traditional cast-in-place beam-column joint.Unlike the bending failure of cast-in-place beam-column joint,the concrete protective layer of the new joint does not fall off,and the whole crack of component develops sufficiently.The stiffness,bearing capacity and degradation of the new prefabricated joint are better than those of cast-in-place joint.The ductility of the new prefabricated joint meets the requirement,but it is less than that of cast-in-place joint.The energy dissipation capacity of the new prefabricated joint is similar to that of cast-in-place beam-column joint.In addition,in the course of the test,the concrete and transfer steel plates in the connection area of the new prefabricated joint are peeled off to varying degrees under the displacement loading at the end of the beam,which indicates that the bonding between the transfer steel plates and the concrete should be taken seriously in the fabrication of the components,so as to enhance the reliability of the connection between the two.(2)The minimum anchorage length of embedded section steel in the beam of new beam-column joint is determined.From the results of experiment and numerical simulation,it can be concluded that the different length of embedded section steel in beam has no obvious influence on the failure mode,bearing capacity degradation and energy dissipation coefficient of the joint,but it has great influence on the stiffness,ductility and bearing capacity of the joint.When the length of embedded section steel is too small,the stiffness and bearing capacity of the joint decrease obviously,and the ductility decreases.The minimum anchorage length should not be less than 300 mm.(3)The effects of different parameters on the seismic behavior of the new beamcolumn joint are obtained.The retained length of section steel in connection zone needs to match the stiffness of prefabricated beam,otherwise the bearing capacity of the joint will decrease and the effect of force transmission will be poor,so it is more appropriate to choose 200 mm;too small thickness of conversion steel plate will lead to the decrease of bearing capacity of prefabricated beam-column joint,and the minimum thickness should not be less than 16 mm;the thickness of welded plate in connection zone,the spacing between stirrups of prefabricated beam and the axial compression at the top of column have little influence on the mechanical properties of the new beam-column joint.(4)A more reasonable design method and construction requirement for the new beam-column joint of prefabricated RC frame are put forward.The diameter of longitudinal reinforcement in prefabricated beam should not be too small;weld strength of section steel in connection zone should meet the checking calculation requirement of formula in this paper;transfer steel plate is welded with studs to strengthen its connection with concrete.The arrangement and diameter of studs should meet the requirements of the paper;it is suggested that the construction of medium-sized steel skeleton should be cast in one time to ensure the quality and improve the stress of joint. |
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