Report - PEER - University of California, Berkeley

emain the same, the magnitude of sliding displacement is less for equipment withhigher µ and φ values.Probability of exceedenceProbability of exceedences1.00.80.60.40.2(a)DM = 5 cmµs= 0.3, φ = 0.5µs= 0.3, φ = 0.9µs= 0.7, φ = 0.5µs= 0.7, φ = 0.90.00.0 0.5 1.0 1.5 2.0 2.5Peak horizontal floor acceleration (g)1.00.80.60.40.2(b)DM = 10 cm0.00.0 0.5 1.0 1.5 2.0 2.5Peak horizontal floor acceleration (g)Probability of exceedenceProbability of exceedence1.00.80.60.40.2(c)DM = 30 cm/s0.00.0 0.5 1.0 1.5 2.0 2.5Peak horizontal floor acceleration (g)1.00.80.60.40.2(d)DM = 50 cm/s0.00.0 0.5 1.0 1.5 2.0 2.5Peak horizontal floor acceleration (g)Figure 3. Effect of µ andsφ on seismic fragility curves, considering differentDMs.4.2 Effect of Building Characteristics on the Fragility CurvesTo study the effect of the dynamic behavior of different building structures on thefragility curves, two additional 8-story building models are constructed. Thesebuildings, with a steel moment resisting frame (SMRF) construction; have beenpreviously considered by Santa-Ana and Miranda (2000). Both structures have thesame floor plan consisting of three bays in each direction. However, column andbeam details vary between the two buildings, such that one is relatively flexible,while the other is relatively stiff. The buildings have a uniform mass distribution anda non-uniform lateral stiffness distribution over their height. They were designedusing the lateral load distribution specified in the 1994 Uniform Building Code(ICBO, 1994), with member stiffness tuned to obtain fundamental periods ofvibration for each structure representative of those obtained from earthquake recordsof instrumented existing SMRFs. The fundamental periods of vibration for these twostructures are T 1 = 1.92 and 1.19 seconds, for the flexible and stiff structures,respectively. In the following discussion, the nomenclature Steel-1 and Steel-2 is usedto refer to the flexible and stiff structure, respectively.Numerical models of these structures were developed in OpenSees (2003) forthese structures, considering a representative 2D frame of the building in thetransverse direction [Figures 4(b) and (c)]. Both geometric nonlinearity and materialnonlinearity are accounted for the model. A lumped mass model is used, with thebuildings assumed fixed at the ground surface. Two percent Rayleigh massproportional damping is used and kinematic material hardening is assumed.204