Balanced design philosophy of superior high-performance steel cover-plated beam-to-column joints

Superior high performance (SHP, 460 MPa or 690 MPa grade) steel, combining high strength, low yield-to-tensile strength (Y/T) ratio, excellent ductility, corrosion resistance and fire resistance was recently developed in China. The seismic response and design of SHP steel beam-to-column joints reinforced with cover plates under cyclic loads are investigated in this paper. Three full-scale SHP460 specimens were carefully designed and tested, with two parameters, including the axial compression ratio and weld access hole, being varied and studied. The test setup and procedures, together with the key obtained results, including load–deformation curves, failure modes, loading resistance, stiffness, as well as ductility are fully reported and discussed. The components of the story drift angle θd are thoroughly analysed, and the contribution of each part to energy dissipation is evaluated. Digital image correlation (DIC) is used to quantify the deformation of the panel zone (PZ), which is more accurate than traditional contact measurement methods. Furthermore, the experiments were supplemented by numerical simulations; finite element models were firstly developed to replicate the experimental behaviour and then employed to perform parametric studies to generate further numerical data on SHP steel beam-to-column joints covering a wide range of axial compression ratios, thicknesses of PZ and material properties. Based on the test and numerical data in this paper, in conjunction with available results of other researchers, a strength and ductility-based balanced design strategy is proposed. It is beneficial for understanding, predicting, and controlling the failure modes and yield mechanisms between the shear yielding of PZ and the flexural yielding of beam and can be described by the balanced coefficient βpz. •Full-scale beam-to-column joints using superior high-performance steel are tested.•Effects of axial compression ratio and geometry of weld access hole are clarified.•Prediction equation is proposed for initial rotational stiffness of the joints.•Effects of panel zone yielding on the seismic performance are evaluated.•Combined strength- and ductility-based design guidance is developed.