Simplified Estimation of Seismic Life-Cycle Costs

Most seismic risk assessments for economic decision-making of commercial buildings are based on a risk metric called probable maximum loss (PML) that is associated with losses from an earthquake shaking severity with a 500-year return period. For various reasons, PML is a poor metric for economic performance assessment. This paper introduces an analogous measure, the probable frequent loss (PFL), defined as the mean loss resulting from shaking with 10% exceedance probability in 5 years (an approximately 50-year event). It overcomes many of the problems of PML, and offers the advantage that expected seismic life-cycle costs and expected annualized loss are approximately proportional to PFL through a seismic hazard coefficient that depends on site characteristics, fundamental period, and damage shaking threshold, and can be tabulated for ready use. A brief review is given of a building-specific seismic vulnerability method that may be used to calculate PFL.