HHT-Based Artificial Seismic Accelerograms Generation

Part 11: Simulations and Fuzzy ModelingInternational audienceA new efficient approach for generating spectrum-compatible seismic accelerograms is proposed. It is based on the Hilbert-Huang Transform (HHT); one natural seismic accelerogram is decomposed into frequency and amplitude components. The components are appropriately modified to synthesize the artificial seismic accelerogram that appears to have compatible acceleration spectrum with the natural seismic accelerogram. The HHT is an adaptive signal processing technique for analyzing nonlinear and non-stationary data such as seismic accelerograms. With HHT a seismic accelerogram is decomposed into a finite and small set of components. These components have well defined instantaneous frequencies, estimated by the first derivative of the phase of the analytic signal. The method is tested using twenty natural seismic records and a comparison with two established methodologies is provided

Influence of Ground Motion Duration on Responses of Concrete Gravity Dams

This study investigates the duration effect on the responses and damage of a dam–reservoir–foundation system. A group of 95 recorded accelerograms with a wide range of durations are adopted in the analyses. A novel global damage index that takes into consideration the consequences of damage at different locations on the overall dam safety is proposed. Nonlinear analysis results show that the duration is positively correlated with the accumulated damage of the dam system. An amplification coefficient that relates the response of the concrete gravity dam from short-duration and long-duration ground motions is proposed

Recording and interpreting earthquake response of fullscale structures

Earthquake resistant design (or retrofit) of structures requires realistic and accurate physical and theoretical models. Validation and further improvement of these models can be done only by comparison with full-scale, in situ measurements of the response to earthquake excitation. This paper presents (a) a review of the principles this validation process is based on, (b) discussion of selected examples of past contributions to modeling of structures, and (c) an outline of some of the current research needs. It is concluded that, in the education of future engineers, the art of modeling full-scale structures, and breadth of knowledge in classical mechanics have been neglected, and that this trend should be reversed. 1