PROBABLE MAXIMUM LOSS ESTIMATION IN EARTHQUAKES - AN APPLICATION TO WELDED STEEL MOMENT FRAMES

An approach to the evaluation of the damageability of buildings and th e 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 sp ecified number of years from earthquake ground shaking. A Markov Model developed is used in a Monte Carlo simulation to determine damage sta tistics, from which PML values are determined. Four sites within the L os Angeles area are considered, as are a range of building damageabili ties from very low to very high. Specific assessments are made for wel ded steel moment frame buildings representative of the post-Northridge understanding of damageability. PML values are shown to be very sensi tive to the probability of loss exceedance, the time period considered , the number of buildings in the portfolio, and the lower bounds of ea rthquake magnitude and ground motions considered. The number of buildi ngs considered in the PML assessment is shown to be very important as a means of reducing PML values. The use of MMI ground motion character ization is assessed and found to be wanting. A comparison of PML resul ts with other damageability measures (both average and 10% exceedance) for four sites, including different ground motions and earthquakes, a nd a maximum probable loss associated with the closest serious earthqu ake, indicates that these other measures are not good estimators of th e full probabilistic PML that considers in a consistent manner both si te ground motion and building performance uncertainty. (C) 1997 by Joh n Wiley & Sons, Ltd.