Lumped vs Distributed Plasticity in Terms of Parameters Used in Seismic Codes and Seismic Design

A comprehensive study is performed for moment steel frames, designed according to the Mexico City Code (MCC), considering the lumped plasticity (LP) formulation and compared with that of distributed plasticity (DP). Bending moments and interstory shears are underestimated by up to 40% using the LP approach; however, axial loads in interior columns are precisely estimated. The magnitude of seismic reduction factor (Q’) values specified in the MCC are not justified. Nor is the assumption of the same reduction for all parameters. The DP formulation and the step-by-step nonlinear seismic analysis are suggested to estimate the responses of the studied structural system.