Report - PEER - University of California, Berkeley

Table 1. Properties of the 4 WallsWallEII / ΣIM y (kN)M y /ΣM y13.45x10 70.0667157520.109726.90x10 70.1333250080.1742313.8x10 70.2667398220.2773427.6 x10 70.5333630080.4388∑51.75x10 71.00001435901.0000The shear demands at the wall bases obtained from the several alternativeanalyses (mean values for the 10 records), including pushover, are listed in Table 2.Comparing the Ten Storey BH and MH columns it is evident that forcing the hinge todevelop solely at base (BH) results in higher shear demands than when hinges areallowed to develop at higher levels (MH). Linear analysis — after division by thestrength reduction factor R (≈ 4.2) — underestimates the shear forces on the walls.Cyclic pushover (PO) with inverted triangular loading, including the effects of theUBC modified accidental eccentricity, leads to rather poor approximation since itignores the effects of higher vibration modes. Pushover analysis, in which the lateralforce resultant is located so as to account for higher modes and R (Rutenberg et al.2004) in an isolated wall — again using the peak values resulting from the factoredaccidental eccentricity — does improve the wall results appreciably.Single storey nonlinear results are far off the mark, whereas their linearcounterparts are similar to the M-DOF ones. As noted, base shear demand is stronglyaffected by the higher vibration modes, and is increasing with R, hence 1-storeyresults cannot predict it. One might be tempted to use the undivided (by R) linearresults as a first approximation, but the similarity appears fortuitous.From the above it appears that the point load Cyclic PO approach deservesfurther consideration.Table 2. Comparison of wall shear forces at base (kN)Wall1TenStoreyBH#4071TenStoreyMH3138TenStoreyLin/R947CyclicPOTriang.2212CyclicPOPoint3339OneStoreyNonlin.993OneStoreyLin/R9652583656541224298249231578126631267694621540720397362533150049356648319533875741039682459BS1092710743439733851905090134878375