Seismic performance of irregular-shaped concrete-filled steel tube column to H-shaped steel beam joints with inner semi-diaphragm: Experimental and numerical study

Abstract

This paper proposes a new kind of irregular-shaped concrete-filled steel tube columns to H-shaped steel beam joints with inner semi-diaphragm (ICFSTC-Joint). The inner semi-diaphragms are welded with the inner surface of the column wall, directly opposite to the flange of the H-shaped steel beam, ensuring tensile force from the beam flange to go directly into the semi-diaphragm. Firstly, the experiments of two L-shaped and two T-shaped ICFSTC-Joint (L-Joint and T-Joint) specimens under different axial compressive ratios are carried out to investigate their hysteretic behavior and failure mode. The experimental results show that the proposed ICFSTC-Joint could effectively improve the hysteretic performance, bearing capacity and stiffness of CFST column joints and can realize that the beam yields before the joints fail. It is obsereved that the axial compressive ratio of the column, as a key parameter, influences the hysteretic behavior of ICFSTC-Joint significantly. Secondly, the FE models of L-Joint and T-Joint are established and verified by the experimental results. The hysteretic curves and skeleton curves of ICFSTC-Joint FE models are obtained and agree well with the experimental curves. Finally, a parameter analysis is carried out by using established FE model to investigate the influence of inner semi-diaphragm on the hysteretic behavior of ICFSTC-Joint, involving the height and thickness of inner semi-diaphragm. A recommended value of the size of diaphragm is given for engineering design. This paper provides reference for engineering design of irregular-shaped CFST column-beam joints and further study on their design method.