Damping Ratios of Reinforced Concrete Structures Under Actual Ground Motion Excitations

Abstract

Structural damping ratio which quantifies the energy dissipation of civil structures under external excitations plays a critical role in the seismic design and assessment of civil structures. In existing building design provisions and guidelines, however, the structural damping ratio is only suggested either as a single fixed value or as an optional value for the general structure type adopted. For example, damping ratio 5% is commonly recommended for all reinforced concrete (RC) structures in practical seismic design, which may not be sufficient to represent the realistic damping features of different RC structures under ground motions with different amplitudes. This research explored deeper understandings on the structural damping features of different RC structures under actual ground motion excitations. A series of seismic response records of RC structures were collected from the “Center for Engineering Strong Motion Data” (CESMD) database. These records were then categorized into three typical lateral resisting systems: moment-resisting frame systems, shear wall systems, and moment-resisting frame plus shear wall systems. The equivalent structural damping ratios for different systems of RC structures were then estimated based on the categorized response records with different amplitudes. Finally, an empirical statistical relationship was established, offering a refined basis for civil engineers to reasonably choose the equivalent damping ratios during the design and post-earthquake assessment of the RC structures.