The Influence of Numerical Model Refinement on the Prediction of the Spatial Formation of Plastic Hinges in a Moment-Resisting Frame

Ductile behavior of the materials applied in seismic structural design is highly appreciated. During damaging response, the structures shall form well controlled plastic hinges. The localization of these hinges is critical for ensuring the integrity of beam–column connections. However, solving this task creates a numerically exhausting problem, requiring various levels of precision modeling. This study investigates the variation in plastic hinge spatial formation using a single-story steel frame numerical model with three distinct numerical environments: SAP2000 (lumped plasticity), SeismoStruct (distributed plasticity), and Abaqus (3D solid modeling). Nonlinear static pushover and nonlinear time history analyses (NTHA) were performed across varying seismic intensities. The results indicate discrepancies between simplified engineering models and the 3D solid model and reveal that the plastic hinge center position (xPH) is not stationary; its location fluctuates based on the intensity of excitation and the extent of local flange buckling. Furthermore, the inter-story Drift Ratio (IDR) analysis shows the lumped model tends to underestimate peak displacements in relation to the solid model by even 26%. This research emphasizes the need for a reasonable selection of a numerical model to perform the analyses required for SHM system design, as well as implications for damage indication and frame assessment after a seismic incident.