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This paper aims to investigate the seismic and post-seismic behaviour of a new and innovative type of through-beam connection between a concrete-filled steel tubular (CFST) column and a reinforced concrete (RC) beam. In this new connection system, the steel tube is completely or partially cut with the cut or openings being at the corresponding beam location, with the longitudinal steel reinforcing bars for the beam remaining continuous through the connection region. A strengthening ring beam is used to enlarge the connection zone in order to compensate for the possible decrease of the axial load carrying capacity as a result of the discontinuity of the steel tube that encases the column. Cyclic loading tests and subsequent axial compressive tests are reported on six beam–column specimens. Based on the experimental results, the hysteretic response, the skeletal and post-cyclic static load–deflection curves, the strain, ductility, strength and the stiffness degradation and energy dissipation are discussed. The favourable seismic performance of the connection is demonstrated in the tests. A finite element model is then developed and validated by a comparison with the experimental results. The relative effects of the reinforcement ratio of the frame beam and the ring beam, and the axial compressive force in the column on the seismic behaviour of the connection are elucidated through parametric studies. [ABSTRACT FROM AUTHOR]

This paper investigates the axial compressive behaviour of T-shaped concrete-filled steel tube (CFST) stub columns with blinding bars. In this column system, binding bars are applied cross-through the section and produce confinement effects. Eleven specimens with binding bars and five ones without binding bars were tested under axial compressive loading. The experimental results demonstrate that, by setting binding bars, the local buckling failure modes are changed and the occurrence of local buckling is delayed, and the global outward bulge of the steel tube at the concave corners can be effectively restrained. The ultimate strength and ductility of the columns with binding bars can achieve up to 1.53 and 7.5 times higher than those of the columns without binding bars, respectively. Taking into consideration the contribution of binding bars, the confinement effects of steel tube and the other sectional characteristics, a method for predicting the ultimate axial compressive strength of the columns with or without blinding bars is established. The accuracy of the method is validated through comparisons of the experimental results reported in this paper and in other available open literatures. [ABSTRACT FROM AUTHOR]

This paper investigates the seismic behaviour of a new type of through-beam connection between a square concrete-filled steel tubular (CFST) column and a reinforced concrete (RC) beam. In this new connection system, the steel stub is completely interrupted in the connection zone, with longitudinal steel bars of the frame beam being continuous through this zone. The connection incorporates a strengthening joint system with a steel cage consisting of multi-layer steel meshes and radial pattern stirrups to compensate the possible decrease of strength of connection due to the interruption of the steel tube. The connection is rigid with the integrity and continuity of the columns and beams. Cyclic loading tests on five beam-column specimens are conducted to evaluate this new connection. The hysteretic response, the skeletal and load–deflection curves, the strain, ductility, strength and the stiffness degradation and energy dissipation are obtained. Experimental results demonstrate the favourable seismic performance of the connection including their superior ductility and energy dissipation capacity. A sophisticated solid finite element model is developed and verified by comparing with the experimental results, and being applied for further parametric studies. A simple fibre finite model using OpenSEES is also proposed and the efficiency and accuracy of the model are illustrated. [ABSTRACT FROM AUTHOR]

To improve the strength and ductility of the core walls in high-rise buildings which would be subjected to combined high axial compressive force and bending moment during the earthquake, an innovative concrete filled double-skin steel-plate composite (CFDSC) wall is proposed. The CFDSC wall is composed of the concrete filled double-skin steel-plate wall body with transverse stiffeners, vertical diaphragms and distributed batten plates welding on the internal surface of the double steel plates, and the concrete filled steel tube (CFST) columns including a pair of CFST columns positioned at the end of the cross section as boundary elements and an additional one located in the central section of the wall. Five CFDSC wall specimens were tested under constant axial compressive force and lateral reversed cyclic loading to investigate the seismic behaviour of the wall considering the effect of axial force ratio and shear span ratio. The favourable seismic performance of the CFDSC walls was demonstrated in the test. No serious pinching effect was observed on the hysteresis curves of all the specimens. The drift ratios corresponding to the ultimate stage were recorded as being in the range from 1/67 to 1/30 and the ductility coefficients were varied from 4.50 to 8.22. The experimental results manifest that the CFDSC walls have great energy dissipation capacity. Formulae for calculating the lateral load-carrying capacity of the CFDSC wall, taking the confinement effects from steel plates into account, were proposed. The results calculated by the proposed method show good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: This paper is concerned with the axial load behavior of L-shaped concrete-filled steel tubular (CFT) stub columns with binding bars provided to improve the mechanical behavior of these elements. Six specimens with binding bars and one specimen without binding bars were tested to examine the effects of horizontal spacings and diameters of binding bars, and width-to-thickness ratios of steel plates on the failure modes, maximum strength, and ductility of L-shaped CFT stub columns. Experimental results demonstrate that the local buckling of the steel tube can be delayed by setting binding bars, the confinement effects on the core concrete can be improved significantly, and the bearing capacity and ductility of the L-shaped CFT stub columns are enhanced by 7% and 26%, respectively. Based on a constitutive model of confined concrete, a method for calculating the maximum strength of L-shaped CFT columns with and without binding bars is proposed. The method is verified with experimental results from this test program and data from other experiments. The results predicted by the proposed method show better agreement with the experimental values than the values predicted by AISC (2005), BS5400 (2005), EC4 (2004) and GJB (2001). [Copyright &y& Elsevier]

• An innovative precast reinforced concrete shear wall with bolt-plate connection was proposed. • Horizontal cyclic loading tests on the precast walls were conducted. • The seismic performance of the precast walls was examined. • Design methods for the precast shear walls were proposed. The seismic resistance of an innovative precast reinforced concrete shear wall with vertical plates along its bottom edge to be bolted to plates protruding from the foundation was tested in reduced-scale model in the laboratory. Five precast shear walls with different wall heights and axial loads, as well as one reference cast-in-place shear wall, were tested. Horizontal cyclic loading was applied to examine the seismic performance of the specimens. The failure modes of the shear walls are discussed, along with their hysteretic behaviour, stiffness degradation, energy dissipation capacity, slip at the bolted connections, and strains in the reinforcement and in the connecting plates. The test results show that the bolted-plate connections can effectively transfer vertical and shear forces, as well as bending moments, to the foundation beam without any slip along the connection. The precast specimens exhibited approximately the same seismic behaviour as the cast-in-place one. In general, the failure mode shifts from compression-bending to shear-compression at smaller heights of the walls, with an increase in the bearing capacity, but a reduction in wall deformability and the energy-dissipation capability. At smaller values of the axial loads, the bearing capacity decreases but the deformability increases. The existing Chinese design code for normal reinforced concrete shear walls gives safe design limits also for the precast walls with bolted-plate connections. [ABSTRACT FROM AUTHOR]