Report - PEER - University of California, Berkeley

21.510.5021.510.50solutions (obtained from statistical studies reported in Medina 2003). From themiddle graph it is evident that any solution with T 1 = 1.8 sec. would cause losses atthe 50/50 hazard level that by far exceed the acceptable losses. In fact, the three T 1 =0.9 sec. design solutions barely meet the loss target, i.e. solutions with T 1 > 0.9 sec.are discarded. In the three presented T 1 = 0.9 solutions the base shear strengthcoefficient γ = V y /W is varied from 0.3 to 0.2 and 0.1. [The fact that the threesolutions overlap for a large range is a consequence of adherence to the equaldisplacement rule.] Only the γ = 0.3 solution is attractive because for solutions withsmaller γ values the ratio [S a (T 1 )/g]/γ is much smaller than 1.0 (S a (T 1 )/g is close to 0.3at the 50/50 hazard level), which indicates considerable inelastic response of the SSsystem at the 50/50 hazard level. This would move the SS loss curve far to left, makeit steeper, and make the SS losses unacceptable.Sa(T 1 )/g2.0Sa(T 1 )/g2.0T 1 =0.9sec.T 1 =1.8sec.1.51.01.51.0T 1 =0.9 sec.γ=0.3γ=0.2γ=0.10.50.5T 1 =1.8 sec.γ=0.3γ=0.2γ=0.150/5010/50Sa Mean Hazard2/50Curves, H(Sa(T 1 ))0 0.0 0.005 0.01 0.015 0.02 0.0250.030 0.00.5 1.0 1 1.5 2.02Mean Sa(T 1 )-IDR CurvesMean Sa(T 1 )-FA CurvesExpectedSubsystem LossNormalized by TotalReplacement Cost1.00.80.60.40.2NSDSSSS0.050.00.0 0.005 0.01 0.015 0.020.025EDP=Avg. of max.story drift ratios, IDRNSASS0.00.5 1.0 1.5 2.0EDP=Avg. of max. flooraccelerations, FA(g)Figure 3. Example of design decision support based on targeted acceptablelosses.The merits of the T 1 = 0.9 and γ = 0.3 solution can be assessed further byinspecting the expected SS and NSDSS losses at other hazard levels, such as the 10/50and 2/50 levels, as illustrated in Figure 3. The upper right graph can be utilized to512