| Reinforced concrete structure is the most commonly used structural form in China’s construction industry,mainly cast-in-situ concrete structure.In recent years,with the emergence of labor costs,construction site environmental pollution,sustainable development and other issues,the assembled reinforced concrete structure has attracted more and more attention from the engineering community because of its advantages of short construction cycle,material saving and less environmental pollution.However,the problems of poor overall performance,complex load transfer path and easy assembly and disassembly of assembled reinforced concrete structures hinder the development of assembled concrete structures.In this paper,a new type of prefabricated loading-unloading concrete beam-column joint was proposed based on the principle of equal strength,strong joints and weak members.The main contents and some important conclusions are as follows:(1)Based on the research status of assembled beam-to-column joints at home and abroad,a new type of prefabricated loading-unloading beam-to-column joints is proposed,and the purpose,content,significance and method of this paper were clarified.(2)Connection design of new loading and unloading beam-column joints.Referring to the connection design of steel structure,this new type of joint is composed of prefabricatedreinforced concrete beams and columns and connecting steel,including I-steel connectors with cladding plates and bolts,bolts and upper and lower connecting steel plates.In the middle of the precast concrete column,there is a 260 mm cantilever beam structure.The I-shaped steel connector is located on the beam and precast at the cantilever beam structure and the end of the precast beam.The cladding plate with bolts is welded to the steel bar in the beam.(3)ABAQUS model of new prefabricated loading-unloading beam-column joints and cast-in-situ joints is established,monotonic load and reciprocating load are applied,and seismic performance parameters such as hysteretic curve,skeleton curve,ductility and energy dissipation performance are compared and analyzed.The results showed that under uniaxial displacement loading,the new prefabricated loading-unloading beam-column joint reduces the stress concentration at the beam-column junction,thus transferring part of the stress to the prefabricated beam end,which improves the safety and stability of the core area;the bearing capacity of the new prefabricated loading-unloading beam-column joint is 0.05% lower than that of the cast-in-situ joint,and the ductility of the loading-unloading joint is 9.38% is lower than cast-in-place joints,and the energy consumption is 0.07%.Generally,the performance of the new loading-unloading beam-column joints meets the design concepts of "strong column and weak beam,strong joint and weak member.(4)The parameters of four groups of 11 models including the position of I-beam joint,the length of cladding plate,the axial compression ratio and the position of loading point are analyzed,and the reference and suggestions for joint design are given.The results showed that the distance between I-shaped steel connector and column end is between 110 mm and200mm,which is a desirable range;the farther I-shaped steel connector is from column end,the seismic performance will approach to cast-in-place joint,but it is not desirable because the cantilever beam length is too long,it is not easy to load and hoist;the cladding board length is desirable within 150mm-200 mm,and the longer the cladding board length is,although it can improve its bearing capacity,but its extension is not desirable.The brittle failure is prone tooccur because of the excessive reduction of both properties and energy dissipation capacity.The yield load and ultimate load increase by 1.27% and 3.93% respectively when the axial compression ratio is within 0.2-0.8,but the delay of 0.8 is reduced,so it is not advisable. |
