Damage Spectra: Characteristics and Applications to Seismic Risk Reduction

Abstract

Improved damage spectra are proposed to quantify the damage potential of recorded earthquake ground motion. The damage spectra are based on a combination of normalized hysteretic energy and deformation ductility of a series of inelastic single-degree-of-freedom systems. The damage spectra proposed will be zero if the structure remains elastic, i.e., no significant damage is expected, and will be unity if there is a potential of collapse. By varying a coefficient in their formulations, improved damage spectra can be reduced to commonly used normalized hysteretic energy or displacement ductility spectra. The damage spectra are computed for hundreds of horizontal ground motions recorded during the Landers and Northridge earthquakes. Source-to-site attenuation of the damage spectra in the Northridge earthquake is examined. Calibration of the damage spectra for an instrumented building damaged during the Northridge earthquake is also carried out. The improved damage spectra are promising for assessment of the performance-based seismic vulnerability of existing structures. For example, following an earthquake, near real-time contour maps of damage spectral ordinates at selected periods provide useful information on the spatial distribution of the damage potential of recorded ground motion for specific types of structures. The concept of damage spectra is also promising for carrying out performance-based design of new structures.