DYNAMIC PARAMETER SIMILITUDE FOR CONCRETE MODELS

This paper reports the results of a series of experimental modal analy ses that were performed to examine the similitude of the dynamic param eters (resonant frequencies, mode shapes, and modal damping) of reinfo rced concrete replica models. Also reported are the similitude require ments for damping forces that were developed as part of this study. Al though damping is typically considered a material property, the simili tude analysis shows that both material properties and system geometry must be considered when scaling the damping forces. Results of the exp eriments show that the modal frequencies and the mode shapes of a prot otype structure can be accurately predicted from tests on scale-model structures. Variations in equivalent viscous damping ratios identified on models and prototype were greater than variations for the other me asured dynamic parameters. However, all damping ratios were less than 2 percent of critical, and the observed variations would not significa ntly alter the dynamic response of the structures.