Report - PEER - University of California, Berkeley

IDR 3[rad]0.100.080.060.040.020.00(a)0 1020304050∆ i [cm]medianσ IDR30.60.40.20.00 1020304050∆ i [cm]PFA 4 (g)2.01.61.20.80.40.0median0.0 0.4 0.8 1.2 1.6PGA [g]σ PFA40.6(d)0.40.20.00 0.4 0.8 1.2 1.6PGA[g]Figure 2. (a) Variations of median and dispersion of IDR 1 with changes in theinelastic spectral ordinate, ∆ i ; (b) variations of median and dispersion of PFA roofwith changes in PGA.Figure 2a presents the variations of the median and dispersion of IDR 1 withchanges in IM, when using inelastic spectral ordinates ∆ i (T 1 ) as the intensity measure.Comparison of figures 1 and 2 shows that using ∆ i (T 1 ), as the intensity measure leadsto lower levels of dispersion for IDR 1 , particularly at higher level of intensity. Figure2b shows the variations of peak floor acceleration demands at the roof when PGA isused to characterize the ground motion intensity. Comparing figure 1 and 2 showsthat using PGA as the intensity measure leads to lower levels of dispersion than thosecomputed when S d (T 1 ) is used as IM. This agrees well with previous observations,which indicate that when a significant portion of the exposed value is sensitive tofloor accelerations (e.g., in museums, clean rooms, laboratories, etc.) accelerationbasedintensity measures lead to smaller dispersions in response and hence a smallernumber of ground motions may be used (Taghavi and Miranda 2003b).3.2 Damage Estimation(b)Once the response of the structure has been computed, an estimation of the damage inindividual components can be obtained through the use of fragility functions. Fragilityfunctions are curves that permit the estimation of the probability that a structural ornon-structural component will be in a certain damage state when it is subjected to acertain level of EDP.For each component, damage states, referred in PEER as damage measures DM,associated with different repair actions were identified. Fragility functions for eachdamage state were then developed using the results of experimental results availablein the literature. Many studies have concluded that the structural response parameterthat is best correlated with structural damage is the interstory drift ratio, IDR.Therefore, this parameter was used to develop fragility functions of structuralcomponents. Analysis of the results of various damage states indicates that fragilityfunctions can be assumed to have a lognormal distribution. Therefore, only twoparameters, namely the median and logarithmic standard deviation of the EDP, arerequired to define the fragility function corresponding to a certain damage state.(c)154