Effect of Loading History on Shake Table Performance of A Two-Column Bent with Infill Wall
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The purpose of the study presented in this report was to determine if a typical two-column drop cap bridge bent model with infill wall (B2RW-II) retrofit could withstand a simulated earthquake representing the 1994 Northridge Sylmar earthquake with acceleration amplified by a factor of two. A similar specimen (B2RW) had failed when subjected to this motion in a previous study. Specimen B2RW was tested subjected to a series of earthquake motions with increasing amplitudes in successive runs. The present study was undertaken to compare and evaluate the relative performance of the two bents and determine the effect of the loading history. Both models were tested on one of the shake tables at the University of Nevada, Reno. The results showed that B2RW-II suffered only a minor to moderate level of damage under 2 x Sylmar in contrast to B2RW that failed under the same motion. The maximum displacement ductilities for this run were 2.4 and 6.6 for B2RW-II and B2RW, respectively. Loading of B2RW-II was continued until failure. One aftershock simulating 1.5 x Sylmar and another 2 x Sylmar motion to fail the specimen were applied. The overall load-deflection responses of B2RW and B2RW-II were similar. The ductility capacity of B2RW-II was only slightly higher than that of B2RW. The mode of failure of the two specimens was also generally similar. The only exception was the failure mode in one of the columns, which was affected by the residual displacement of the bents.
Report No. CCEER-04-1