Abstract
In order to acquire the hysteretic behavior of the asymmetrical composite joints with concrete-filled steel tube (CFST) columns and unequal high steel beams, 36 full-scale composite joints were designed, and the CFST hoop coefficient (ξ), axial compression ratio (n0), concrete cube compressive strength (fcuk), steel tube strength (fyk), beam, and column section size were taken as the main control parameters. Based on nonlinear constitutive models of concrete and the double broken-line stress-hardening constitutive model of steel, and by introducing the symmetric contact element and multi-point constraint (MPC), reduced-scale composite joints were simulated by ABAQUS software. By comparing with the test curves, the rationality of the modeling method was verified. The influence of various parameters on the seismic performance of the full-scale asymmetrical composite joints was investigated. The results show that with the increasing of fcuk, the peak load (Pmax) and ductility of the specimens gradually increased. With the increasing of n0, the Pmax of the specimens gradually increases firstly and then gradually decreases after reaching a peak point. The composite joints have good energy dissipation capacity and the characteristic of stiffness degradation. The oblique struts force mechanism in the full-scale asymmetrical composite joint domain is proposed. By introducing influence coefficients (ξ1 and ξ2), the expression of shear bearing capacity of composite joints is obtained by statistical regression, which can provide theoretical support for the seismic design of asymmetrical composite joints.
Highlights
From the structural damage of the Northridge Earthquake in the United States [1], the Hanshin Earthquake in Japan [2], and the Wenchuan Earthquake [3] and the Yushu Earthquake in China [4], it could be seen that the traditional bolt-welded hybrid beamcolumn joints showed poor seismic resistance [5]
In 2014, tests on six concrete-filled square steel tube column–composite beam joints were conducted to studied the seismic performance by Fan et al [6], and the results showed that the joints had good shear capacity, stiffness, ductility, and other seismic behavior
In order to verify the rationality of finite element models of full-scale composite joints with concrete-filled steel tube (CFST) columns and unequal high steel beams, four frame joints with concrete-filled steel square tubular columns and H-shaped unequal height steel beams according to the reduction ratio of 1:3 designed by Xu [19] were selected
Summary
From the structural damage of the Northridge Earthquake in the United States [1], the Hanshin Earthquake in Japan [2], and the Wenchuan Earthquake [3] and the Yushu Earthquake in China [4], it could be seen that the traditional bolt-welded hybrid beamcolumn joints showed poor seismic resistance [5]. In 2014, tests on six concrete-filled square steel tube column–composite beam joints were conducted to studied the seismic performance by Fan et al [6], and the results showed that the joints had good shear capacity, stiffness, ductility, and other seismic behavior. In 2015, low cyclic load test and finite element analysis on special-shaped asymmetrical CFST composite columns–steel beam joints with angle connections was carried out by Liu et al [13], and the results showed that the failure of such joints was caused by the buckling of steel beam flanges in the joint area. In 2017, Mou et al [14] conducted low-cyclic loading tests on seven reduced-scale joints of highly unequal H-shaped steel beam–square steel columns with outer strengthening rings, and the shear capacity, hysteretic performance, deformation capacity, and failure mode of the joint domain were obtained, respectively.
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