Report - PEER - University of California, Berkeley

2.50.1000Spectral Accel. (g)2.01.51.00.550%/50 years10%/50 years2%/50 yearsAnnual Frequency0.01000.0010y = 0.0011x -2.8750.00 1 2 3 4Period (sec)0.00010.100 1.000 10.000Sa(T), gFigure 3. Uniform hazard spectra in fault-normal direction for the I-880 siteand resulting hazard curve.3.2 Seismic Demand (EDP Estimation)All simulations were carried out using OpenSees (2004). Numerous demand measurescan be monitored during the seismic response analysis, however, the eventual choiceis influenced by the damage models that are available to correlate the EDPs todifferent damage states. In this study, the peak tangential drift of the individualcolumns was selected as the primary EDP measure. This was dictated by theavailability of damage measures and corresponding decision variables as indicated inthe next two sections. Once the seismic demand parameters are computed, a best-fitcurve through the median of the natural logarithm of the simulations is determinedassuming a lognormal distribution, as follows:( ) bEDP = a S a(3)A typical set of simulations and the resulting curve-fit is displayed in Figure 4.6.0EDP, drift (%)5.04.03.02.00.84EDP = 1.54( S a )1.00.00.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6IM, Sa (g)Figure 4. Typical set of simulations resulting in EDP-IM relationship.69