Shake table testing of unbonded post-tensioned concrete walls with and without additional energy dissipation

Abstract

Recently an innovative unbonded Post-Tensioned (PT) concrete wall system was developed that consists of a Precast Wall with End Columns (PreWEC). Dynamic testing was conducted to better understand the seismic response of PreWEC systems and to provide further dynamic test results of PT rocking wall systems. Three unbonded PT concrete walls, including one SRW and two PreWEC systems that incorporated O-connector dissipaters were subjected to a suite of seven spectrum compatible ground motions at different intensity levels in addition to three recent ground motions at natural scale. Negligible damage to the concrete wall panels was observed for all three systems throughout the entire sequence of testing. As expected both PreWEC systems demonstrated higher energy dissipation and lateral-load capacity in comparison to the SRW due to the addition of the O-connectors. This resulted in SRW-A experiencing higher average drifts and lower accelerations than the two PreWEC systems. An intensity measure referred to as an ‘Achieved return period factor’ was defined based on comparing the measured table acceleration response spectrum to a target code response spectrum. The increased spread of both peak acceleration and peak drift versus the achieved return period factor for SRW-A in comparison to both PreWEC systems highlights the more sensitive and unpredictable nature of the SRW as a result of limited damping. The measured inherent damping from the white noise tests was found to range between 3.5% and 4.0% for the three walls. Negligible residual drifts were measured for all walls despite higher static residual drifts being estimated from previously performed cyclic testing on identical walls.