Report - PEER - University of California, Berkeley

spectrum. Hence the expected deflection is the same for both brittle and ductilestructures, and the only parameter that HAZUS has available to affect the distributionis the β value, given fixed values of the threshold deflections (Table 4). As the βvalue changes from 0.7 to 1.3, it can be seen from Fig 4 that the HAZUS distributionshape changes from fully ‘Type I’ to something approaching ‘Type II’, although theshape is not as markedly bi-modal as for the brittle base case from this study. Thebeta value for the HAZUS calculation represents a combination of the effect ofground motion (demand) and structural variabilities (β d and β c in Table 3); thecombined effect of β d =β c =0.5 (the base case considered here) is broadly equivalentto a combined β of about 1 to 1.3. It may be noted that there appears to be no obviousreason why brittleness and a high value of structural variability should be linked, andthe Monte Carlo model used here shows a marked advantage in this respect.Finally, two actual damage distributions recorded after Kocaeli were chosen(cases 5 & 6 of Tables 2 & 3, but numbered 4 & 7 in Table 1). The parametersavailable in the model were varied within reasonable bounds to see how closely themodel distribution could match the recorded ones. The two right hand columns forcases 5 & 6 in Table 3 show the parameters chosen; the deflection values of Table 4were assumed to remain applicable. The resulting distributions are shown in Figure10. They are not of course in any way predictions, but the exercise suggests thatreasonable results may be obtained from the model. Whether the building populationrecorded by CAR Ltd really was so much more ductile than that of the populationrecorded by RMS Inc. is of course another question.(a) CAR Ltd data for Izmit (b) RMS Inc data for Izmit South EastFigure 10. Comparison of simulations from this study with Izmit data.5. CONCLUSIONSA weakness in the current HAZUS methodology for predicting earthquake losses isthat it cannot directly account for the effect of structural brittleness or ductility ondamage distributions, and is no better in this respect than intensity based methods.407