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In order to investigate the seismic behavior of steel beam to steel-reinforced concrete filled square steel tubular column connections, five specimens were tested by quasi-static tests. The influences of end-plate thickness, bolt diameter, concrete strength and axial compression ratio on the load-carrying capacity, moment-rotation curve, energy dissipation capacity, load degradation, rigidity degradation, ductility and ultimate failure modes of end-plate connections were analyzed. The experimental results show that these new type of composite connections belong to the category of semi-rigid connections, and the initial rotational stiffness of connections increase with end-plate thickness and bolt diameter, but the utmost rotational capacity of connections decrease with end-plate thickness. The connection shows excellent behavior in terms of ductility and energy dissipation when the strength of connection is controlled by end-plate or steel beam. The load degradation coefficients of all specimens are between 0. 8 and 1.0, varying within a narrow range. Compared with load degradation, the rigidity of specimens degrades seriously. Moreover, the high strength bolt should avoid brittle failure in the design procedure. [ABSTRACT FROM AUTHOR]

The results of an experimental research involving the testing of six bolted moment-resisting connections under simulated seismic loading conditions were presented. The test specimens modeled the interior joint of a moment-resisting frame consisting of concrete-filled double skin tubular column and H-shape steel beams with reinforced concrete slab using high-strength bolts and T-stub connectors. To investigate the seismic behavior of the composite joints, the failure modes, hysteretic performance, shear strength, bearing capacity degradation, rigidity degradation, energy dissipation and strain were evaluated in detail. The test parameters varied including the axial load level on the column, the stiffener, the size of T-stub, the thickness of slab and the reinforcement ratio in slab. The experimental results indicate that the compressive capacity in column and the shearing capacity in joint are improved by the inserted tube. In some extent, the increase of reinforcement ratio in slab (1% ≤ ρ ≤ ρmax) and the decrease of the loading level on the column (n ≤ 0.3) will improve the total energy dissipation and reduce the ductility of joint, without obvious influence on the joint the bearing capacity. The seismic behavior of joint will be affected by the thickness of T-stub flange and the stiffener. [ABSTRACT FROM AUTHOR]