Study On Seismic Performance Of Concrete Filled Square Steel Tube Column-steel Castellated Beam Joint

Both concrete filled steel tubular(CFST)and steel castellated beam(SCB)are ideal building members in engineering because they have good property of mechanics.If they are connected,not only the advantages of each can be realized,but also the yield mechanism of"strong column and weak beam" is easier to achieve.At present,the mechanics properties of outer annular-stiffener type SCB-CFST with circular section has already been carried out,but the reference on outer annular-stiffener type SCB-CFST with rectangular section(OATSCB-CFSTWRS)has not been found.Therefore,the study on mechanics properties and calculation method for designing of OATSCB-CFSTWR is carried out in this paper.The main work done is as the following:Based on the powerful finite element software ABAQUS and the test data of outer annular-stiffener type steel solid beam-CFST with rectangular section,the finite element model of outer annular-stiffener type steel solid beam-CFST with rectangular section is set up,and its load-bearing and failure process under repeated low cyclic load is simulated and analyzed.The simulation results is close to the finished test results,from which it can be seen that the simulation method is also practicable for OATSCB-CFSTWR.Based on the above work,a model of outer annular-stiffener type SCB-CFST with rectangular section and a model of OATSCB-CFSTWR of the same size are set up according to the downsized real structure.By comparing the hysteresis curves,skeleton curves,ductility coefficient and capacity of energy dissipation of these two models under repeated low cyclic load,it can be seen that the seismic performance of OATSCB-CFSTWR is also good and it can achieve the yield mechanism of"strong column weak beam" more easily.So it can be concluded that the OATSCB-CFSTWR has bright future in engineering application.By changing the parameters of OATSCB-CFSTWR,including axial compression ratio,steel ratio,the strength of steel,the strength of concrete,steel ratio,distance from the first spacing hole center to the column,opening rate,distance of two adjacent spacing hole center and width of reinforcement ring,25 OATSCB-CFSTWR are designed,and the load-bearing and failure process of them under repeated low cyclic load are simulated and analyzed.The corresponding hysteresis curves,skeleton curves,ductility coefficient and equivalent viscous damping coefficient are also abstained from the above simulation.It can be seen from the calculation results:the hysteresis curves of these joints are relatively full and have no obvious stiffness degradation;the displacement ductility coefficient is from 4.2 to 5.3;the equivalent viscous damping coefficient is from 0.31 to 0.36;the energy dissipation coefficient is from 1.98 to 2.28.All these results further explained that this type of joint has good seismic performance.Based on the above simulation results,it's quantitatively analyzed how the parameters influenced the hysteretic and skeleton curves.The results show that the parameters,including the axial compression ratio,width of reinforcement ring,the strength of steel,steel ratio,beam to column linear stiffness ratio,opening rate,distance of two adjacent spacing hole center,distance from the first spacing hole center to the column,all have effects on the skeleton curve to different degree.In all influencing factors,the axial compression ratio,opening rate,distance of two adjacent spacing hole center,distance from the first spacing hole center to the column have less influence on the skeleton curve,but the influence of width of reinforcement ring,the strength of steel,steel ratio,beam to column linear stiffness ratio,the intensity of ring plate width,strength of steel,steel ratio and beam line stiffness ratio on the skeleton curve is obvious.Based on the above results,the simplified calculation equation for calculating the flexural bearing capacity,the ultimate flexural bearing capacity and the initial stiffness of OATSCB-CFSTWR are set up by regression.And the accuracy of the simplified equations are verified,which provided a theoretical basis for practical engineering application and the establishment of the relevant code.