Report - PEER - University of California, Berkeley

3.2 Random VariablesFour random variables are considered in this application. These are three materialparameters, the concrete strength and ultimate compressive strain, and the steel yieldstress, and the model error term in Eq. (11). Mean values and coefficients of variationare reported in Table 1. All random variables are assumed to be log-normallydistributed.Table 1. Characterisation of random variables used in the applicationMaterial propertiesMean CoVf 25 [MPa] 0.20cf 450 [MPa] 0.20yεε cc,u0.006 0.35Model uncertaintyεV0.86 0.263.3 Seismic ActionTen rock/stiff soil records are selected from the PEER data base in the magnituderange from 6 to 7 and the distance range from 25 to 60km. The acceleration responsespectra of the two orthogonal components of the un-scaled records are shown inFigure 3. The “stronger” component is defined as that having highest spectralacceleration at the effective fundamental period of the structure T = 0. 8s. In theanalysis the stronger component has been applied along direction Y of the building(see Figure 1, Right). For the determination of the fragility the stronger componentsare all scaled at the same (increasing) intensity, while the weaker ones are kept in thesame ratio to the corresponding stronger ones as for the un-scaled records.1.2Component 1 (weaker)1.2Component 2 (stronger)110.80.8S a[g]0.6S a[g]0.60.40.40.20.200 0.5 1 1.5 2Period [s]00 0.5 1 1.5 2Period [s]Figure 3. Acceleration response spectra of the 10 selected accelerograms(PEER database: URL: http://peer.berkeley.edu/smtcat).227