Design Method For Steel Beam To CFST Column Connections With Through Column Bolts

Concrete filled steel tubular columns are widely applicated in building engineering because of excellent mechanical properties,convenient construction,good fire-resistance and good economic effect.Because of the closed section of the steel pipe,it is difficult to use the common high-strength bolt for steel beam to CFST column connections.So the end-plate welded to the steel beam can be connected with the concrete filled steel tubular column by the through-column bolts.At present,the experimental study has been carried out on the joints between CFST column and steel beam connected with through column bolts.In order to popularize and apply in practical engineering,it is necessary to systematic study theoretic design method of the joints.In this paper,theoretical analysis and numerical simulation are used to study on the joints of initial rotational stiffness,ultimate capacity,moment rotation relationship and design method.Specific research work and the corresponding results are as follows:(1)The initial stiffness calculation model is established by using the component method,the structural form of non-stiffened endplate connection,stiffened endplate connection,extended endplate connection and T-stub connection are considered.The effect of bolt pretension on joint stiffness and the contribution of column flange to joint region stiffness are taken into consideration.The calculation results show that the endplate and bolt is the key components of the influence of joint stiffness.The rationality of the model is verified by comparison with the experimental and finite element results.(2)By using the knowledge of differential equations,a simplified mathematical model of moment-rotation relationship for steel beam to CFST column connections with through column bolts is proposed.The boundary condition of this model can explain the force characteristics of the joints,and easy to calculate.Through the comparison of the experimental moment-rotation curve and the theoretical model,the rationality of the model is proved,the results show that the theoretical model can predict the capacity and the initial stiffness of the joints.The theoretical model provides a theoretical basis for the design of semi-rigid composite frame of concrete-filled steel tubular structures.(3)Finite element models of monotonic loading and cyclic loading of steel beam to CFST column connections with through column bolts were established by ABAQUS software.The stress state and working mechanism of the joints during the loading process were clarified by the result of finite element models,then the influence of each parameter on the moment-rotation curve and the failure model of the joints was discussed in detail,Finally,the practical engineering design proposal is given.(4)In order to facilitate the application of the joints in practical engineering design,on the basis of numerical simulation,theoretical analysis of this paper,relevant codes and research results,the design method of rigid connection of through-column bolt joints was put forward.The main contents of the design method include:construction requirement,capacity requirement,rigid connection design,seismic-proof design and other aspects.