Experimental Study On Seismic Performance Of Self-compacting Concrete Beam-column Joints With Different Strength Levels

In the trend of China 's overall economic strength increasing,the number of high-rise buildings rises sharply every year.In most high-rise buildings,due to the requirements of the seismic code for axial compression ratio limit,the concrete strength of the column is often higher than the concrete strength of the beam and slab.At this time,the core area of the beam-column joint must be poured with concrete at the same level as the column in order to meet the strength design requirements.However,most of the existing experimental studies on this type of joint only remain in the construction method and construction technology,and there is little research on its mechanical properties,especially when the strength grade difference of beam-column concrete is large,the extension length of high-strength concrete in the core area of the beam is studied on the seismic performance of the joint.As an important hub to ensure the stiffness and bearing capacity of the whole building structure,beam-column joints are prone to under-vibration,leakage and insufficient vibration when pouring concrete by manual vibration in the traditional sense,which seriously affects the construction quality.Due to the characteristics of green environmental protection in production and no vibration in use,the application of self-compacting concrete in beam-column joints can effectively solve the insufficient situation of traditional concrete pouring,and also provide strong help for high-rise buildings in achieving energy conservation and emission reduction,green environmental protection and sustainable development.Therefore,it is of great theoretical value and practical significance to study the influence of self-compacting concrete with different strength grades on the seismic performance of beam-column joints.In this paper,under the premise of focusing on the influence of the extension length of high-strength self-compacting concrete in the beam in the core area on improving the seismic performance of beam-column joints,four “ cross” beam-column joints specimens with different strength grades of self-compacting concrete are designed,and the seismic performance tests under low-cycle repeated loading are carried out.The seismic performance indexes such as the failure process,bearing capacity,ductility bearing capacity,ductility performance,capacity,stiffness degradation and energy dissipation capacity of each specimen are compared and analyzed.The results show that the extension length of high strength self-compacting concrete in the core area has no significant effect on the hysteresis curve,cracking load,yield load and ultimate load,but has a great influence on the yield displacement,displacement ductility,stiffness degradation and energy dissipation capacity.When the beam adopts high strength self-compacting concrete at the same level as the column,it has little effect on improving the seismic performance of the joint.On the basis of experimental research,this paper uses ABAQUS finite element analysis software to establish the beam-column joint models of self-compacting concrete with different strength grades,and conducts nonlinear numerical simulation on the seismic performance index of the test.It is found that the test results are basically consistent with the ABAQUS simulation results in general laws.