AbstractAssessment of structural damage state immediately after earthquakes can play an important role in decreasing economic and life losses, and in optimizing decision-making for affected buildings. These advantages highlight the need for rapid, accurate, and automated structural health monitoring (SHM) methods, as well as the need for generalizable model development methods to accurately resimulate nonlinear response to find the root causes of structural damage and identify elements for retrofit. This study tracked lateral stiffness changes for a real instrumented RC building subjected to three damaging earthquakes between 2013 and 2016 using the proven hysteresis loop analysis (HLA) SHM method. An idealized trilinear force–deformation pinching model created from HLA results is proposed to resimulate highly nonlinear pinching behavior of the building under these events. The proposed model facilitates assessment of the pinching region and its characteristics in terms of seismic response, stiffness and strength degradation, and the overall seismic performance of this RC building. Average correlation coefficients between measured and resimulated interstory displacement were 0.90, 0.97, and 0.97 across all stories for the three events, respectively. Resimulated interstory displacement error was less than 4% on average over all stories and events. These good resimulation results further validated the HLA method. More importantly, the proposed model clearly showed how pinching region length and its participation in dissipating energy increases as cumulative earthquake-induced damage increases in the building, potentially helping hide significant damage from typical detection methods. Thus, in addition to presenting a generalizable nonlinear modeling approach for postevent structural assessment, the overall results bring attention to the significant role that pinching plays in seismic energy dissipation and response for RC buildings.