Energy Capacity of Waffle-Flat-Plate Structures with Hysteretic Dampers Subjected to Bidirectional Seismic Loadings

This study investigates the capacity, in terms of energy, of waffle-flat-plate (WFP) structures with hysteretic dampers subjected to biaxial seismic actions. A numerical model was developed and calibrated with the experimental results obtained from shake-table testing carried out on a WFP specimen subjected to biaxial seismic loads. Then the WFP system was retrofitted with hysteretic dampers—slit-plate dampers (SPDs)—and the numerical model was subjected to different sets of ordinary ground motion records to attain different seismic performance levels (SPLs). Each set of records was applied in a sequence of scaled seismic simulations until the SPL of near collapse was achieved. The capacity in terms of input energy and dissipated energy are presented for the different SPLs, taking into account the differences observed under unidirectional and bidirectional seismic loadings. Furthermore, the level of damage (i.e., accumulated plastic deformations), the level of ductility and the relationship between them—expressed as equivalent number of cycles—are also shown for both the WFP system and the hysteretic dampers. The seismic capacity of the WFP system is found to be significantly enhanced by the inclusion of hysteretic dampers.