A Method for Estimating Spectral Displacements Using a Velocity Pulse

Abstract

A method for computing spectral displacements using a single velocity pulse is presented. Bilinear systems with 5% damping were studied under 101 ground motions. Near-fault ground motions with known forward-directivity effects were not included. The systems covered a wide range of vibration periods and included six strength ratios. The results showed that for periods less than or equal to the characteristic period of the ground, spectral displacements were nearly always governed by the ground velocity pulse of largest amplitude. Based on these results, it is shown that spectral displacements can be estimated using a sinusoidal acceleration pulse whose elastic input energy is equivalent to that containing the peak ground velocity. Based on pulse duration and amplitude, a simplified method is proposed to estimate inelastic spectral displacements for periods less than or equal to the characteristic period of the ground. The proposed method provides estimates of spectral displacements that are in very good agreement with those computed from the actual ground motions, and it is shown to be as good a predictor as existing proposals.