Probable maximum loss estimation in earthquakes: an application to welded steel moment frames

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An approach to the evaluation of the damageability of buildings and the determination of probable maximum loss (PML) values is presented and applied to welded steel moment frame buildings. PML is defined as the loss that has a given (usually 10%) probability of exceedance in a specified number of years from earthquake ground shaking. A Markov Model developed is used in a Monte Carlo simulation to determine damage statistics, from which PML values are determined. Four sites within the Los Angeles area are considered, as are a range of building damageabilities from very low to very high. Specific assessments are made for welded steel moment frame buildings representative of the post-Northridge understanding of damageability. PML values are shown to be very sensitive to the probability of loss exceedance, the time period considered, the number of buildings in the portfolio, and the lower bounds of earthquake magnitude and ground motions considered. The number of buildings considered in the PML assessment is shown to be very important as a means of reducing PML values. The use of MMI ground motion characterization is assessed and found to be wanting. A comparison of PML results with other damageability measures (both average and 10% exceedance) for four sites, including different ground motions and earthquakes, and a maximum probable loss associated with the closest serious earthquake, indicates that these other measures are not good estimators of the full probabilistic PML that considers in a consistent manner both site ground motion and building performance uncertainty. © 1997 John Wiley & Sons, Ltd.