New energy based approach to predict seismic demands of steel moment resisting frames subjected to near-fault ground motions

• An energy-based method to estimate seismic demands is proposed.
• A new energy index is introduced for near-fault ground motions.
• The Proposed energy index is well correlated to the maximum inelastic displacement.

This article proposes a new energy-based approach for predicting seismic demands of steel structures at the near-fault sites by introducing the concept of dissipated hysteretic input energy during largest yield excursion (ΔEh). It is defined as the amount of hysteretic energy demand imposed on a structure over a finite time interval between two zero-crossing of bow system velocity. The proposed energy measure, which is dependent both on the characteristics of ground motions and structural system, is shown to be well correlated to the maximum inelastic displacement. In order to estimate the maximum global displacement of a MDOF system to near-fault ground motions, a new procedure is proposed. The steps of proposed methodology are quite similar to those of the Modified Modal Pushover Analysis (MMPA) method. The determination of the peak global displacement demand, however, is based on a different concept. In contrast to other energy-based procedures, this displacement is an actual value equalizing ΔEh to static monotonic hysteretic energy. Finally, the accuracy of the method was evaluated when response values were compared to the results from nonlinear dynamic analysis. There are good correlations between results of these two methods. Indeed more accurate results in capturing seismic demands of typical steel moment resisting frames subjected to near-fault ground motions in comparison with the procedure proposed in ASCE 41-06 are achieved.