Report - PEER - University of California, Berkeley

3. LIGHTLY REINFORCED LIMITED - DUCTILE RC STRUCTURALWALLSThe research of the seismic response of RC walls has been rather limited incomparison to frames. In particular there are few research results related to thin,lightly reinforced and limited ductile walls in low- to medium-rise buildings with highwall-to-floor ratio. Such buildings are typical for central Europe. Recently, shakingtable test of a 5-story cantilever wall designed according to EC8 (Fig. 6) wasperformed in the frame of the CAMUS 3 benchmark project. Large, 1:3 model wassubjected to a sequence of 4 accelerograms. The wall was heavily damaged and closeto collapse after the fourth run (Fig. 7). Blind prediction was made (Fischinger et al.,2004) using multiple-vertical-line-element model (MVLEM). In the frame of thispaper only a few observations related to PBA issues will be addressed.Figure 6. CAMUS 3 test.Figure 7. Damage to the edge of the wall atthe end of the test sequence (CAMUS 3).3.1 Initial DamageWhile MVLEM had demonstrated excellent performance in previous studies, badcorrelation of predicted and experimental results (Fig. 8a) in the first (low level) runcame as a negative surprise. Later it was explained by the benchmark organizers thatthe wall was subjected to additional loading during initial testing of the setup, prior tothe main test. But, since there was no visible damage and the natural frequencies hadnot changed, they considered this preceding loading unimportant. However, if thispreceding loading was considered in the analysis, the match would be very good (Fig.8b). This example demonstrates that in RC structures damage is not easy to observeand define. Such initial damage, influencing subsequent response, might exist inmany actual situations.298