An efficient energy-based approach for identification of velocity-pulse periods

Abstract Reasonable identification of pulse period is essential for near-fault velocity-pulse simulation, structural response analysis, and probabilistic seismic hazard analysis. In conventional response-spectrum-based approaches, the pulse period is commonly defined as the period corresponding to the peak of the spectral velocity or the joint velocity-displacement spectrum. However, these definitions rely on local spectral peaks and are sensitive to high-frequency components, local oscillations, or secondary peaks, which can result in an underestimated or overestimated pulse period for some velocity-pulses. To address this limitation, this study aims to propose a simple yet robust method for identifying velocity-pulse periods directly from the elastic input energy spectrum, which reflects not only the amplitude and frequency content but also the duration and energy content of ground motions. In the proposed approach, the pulse period is defined as the oscillator period that divides the enclosed input-energy-spectrum area into two equal parts along the period axis. To examine the physical reasonableness of the proposed method, the identified period is prescribed in the analytical pulse model, while the remaining four pulse parameters are optimized using a genetic algorithm. The extracted pulse closely reproduces the dominant features of the original velocity time history, supporting the feasibility of the proposed pulse-period identification method. The proposed approach is also validated through comparison with six representative existing pulse-period identification methods, showing generally consistent estimates of pulse period. In addition, its engineering applicability is further demonstrated through seismic fragility analysis of a reinforced concrete frame, and the results indicate that pulse period has a significant influence on structural vulnerability.