Hysteresis Envelope Model of Double Extended End-Plate Bolted Beam-to-Column Joint

In this study, a hysteresis envelope mathematical model for the double extended end-plate bolted beam-to-column joint is proposed. The aim of a proposed joint model is to provide a more realistic behaviour of steel frames under seismic loading by using nonlinear static pushover analysis. The hysteresis envelope model defines the ratios between the monotonic properties of the joints and the properties of the joints during cyclic deformation. The proposed models are based on the hysteresis curves of the joints obtained by numerical simulations. The numerical model takes into account the geometric nonlinearity of the connecting elements, preloading of bolts, contacts between plates and bolts, and nonlinear properties of steel. Nonlinear static pushover analyses of steel frames are performed where the behaviour of the joints is described using the proposed hysteresis envelope models. The results are compared with the nonlinear static pushover analyses of steel frames with a trilinear monotonic joint model. Based on the results, the values of maximum peak ground acceleration for moment-resisting frames with the monotonic model of joints and hysteresis envelope model are estimated.

Performance of extended end-plate bolted connections subjected to static and blast-like loads

In this study, numerical models were developed to predict the behavior of steel extended end-plate moment connections subjected to static and blast-like loading. Two types of extended end-plate connections were considered, stiffened, and unstiffened, with pretensioned bolts. The models were verified by comparing the results with published experimental data. The models were used to compute the moment-rotation curves for the connection under static loading, and then under different blast durations. The pressure impulse diagram and the energy dissipation for the connection under dynamic loading were determined. The failure modes were examined, and the numerical results were compared with the simplified models presented in codes and standards. Improvement in the performance of the connection by adding one or two stiffeners was demonstrated. For the configuration studied, introducing a stiffener increased plastic dissipation energy for blast loading by 45% compared to the unstiffened connection, whereas under static loading, the plastic energy dissipation for stiffened connection, SC2, was higher than the unstiffened connection by 30%. A conservative estimate for the dynamic increase factor (DIF) was found to be 1.2 for steel yield stress and 1.05 for bolt failure.