Adaptation of real earthquake records for their reproduction by a shaking table with limited stroke

Shaking tables with moving platforms are widely used in laboratory testing of structural models and full-sized devices. In most cases, the platform's movement should reproduce real ground acceleration records. However, the stroke of the platform, required for reproduction of real records, is usually rather large. This limitation does not allow an accurate realization of the ground motion by the shaking table. Commonly, in order to overcome this problem, original records are modified, which causes a significant change in the acceleration records' spectra. That is why structural responses to the original and to the modified records are different. A new method for modification of original acceleration records is proposed, in which the original record is corrected by an additional artificial one that changes the shaking platform's displacement. The corrected record is obtained as a sequence of impulses. The magnitude and duration of each impulse, as well as their location on the time scale, are obtained by an optimization procedure. The optimization is implemented according to a performance index, aimed to minimize the influence of the correcting acceleration record on the spectrum of the original one. The proposed method has higher reproduction accuracy, compared to other known methods. Its effectiveness is demonstrated by comparison of response spectra and dynamic behaviors of three multi-story structures subjected to natural and modified seismic excitations.