Research On Seismic Behavior Of Concrete-filled Steel T-Shaped Tubuar Column To Steel Beam Frame Joints

Concrete-filled steel tubular structure is a type of new structure that can use the advantage of steel and concrete.Owing to its good behavior,the new structure is used more and more widely. Along with widely spread use of CFST(concrete-filled steel tube) structure,people have paid more attention to the design of CFSTjoint.Many foreign and domestic scholars process massive research on CFST joint.The research on the concrete-filled steel tubular column-steel beam joints mainly focus on the square or rectangular joints at present,but there are little theory and test research on the special-shaped joints with outer stiffened ring.To understand seismic behaviors of T-shaped concrete-filled steel tubular column-steel beam joints, based on the exterior joints on the top floor of a frame, pseudo-static loading experiment of1/2scaled specimens including three"weak joints" and one "strong joint " were carried out. Force mechanism, bearing capacity, failure mode, strength and energy dissipation of the joints were studied. Based on it, the paper made a preliminary study on shearing capacity of T-shaped joints in the panel zone and discussed the influence of the seismic behaviors to different axial compression ratios.The results indicated that the failure mode of" weak joints" were shearing failure under compression-shear stress, and the failure mode of "strong joints" were buckling failure of steel beam which underwent a large plastic deformation before failure. The bearing capacity of specimens are going up as he axial compression ratios increase.Hysteretic loops are in plump spindle shape and ductility of joints are better than3and equivalent viscous damping coefficients of all specimens range between0.42and0.52that reflects good seismic behavior.Before yielding, stiffness degradation is not obvious.when the joints begin to yield, stiffness is degrading to some degree and is more obvious as the axial compression ratio increases.The research results of T-shaped joints in the paper can provide reference data for studies of special-shaped concrete-filled steel tubular column-steel beam joints and relevant theoretical bases for design procedures of joints as well.