Improving Resilience of Low-rise Precast Concrete Wall to Foundation Connections

Abstract

Precast concrete panels are commonly used in construction because they can generally speed up construction, reduce the amount of site work and achieve a high level of quality control. The industrial and commercial construction sector is no exception. Slender precast concrete walls are extensively used in New Zealand and around the world for single storey warehousetype buildings for industrial and commercial use. These type of wall panels typically rely on dowel type reinforcement connections to transfer the lateral load demand of the wall to the foundation. However, following recent earthquakes events in Christchurch and Kaikoura, damages were observed in slender precast wall panels, particularly in their connection with the foundation. A series of experiments revealed that some of the commonly used dowel type connection details used in the industry lack reliable load path for the transfer of lateral load demand in the out-ofplane direction. Concrete tension can develop in the connection region when the wall panel is subject to out-of-plane action. This means that in the out-of-plane direction, the panels connections are susceptible to sudden failure in a brittle way, which is not compliant with the concrete design standard in New Zealand. With the aim to improve the resilience of slender precast panel to foundation connection, two alternative details were developed in this study. The design was based on various design standards and guidelines, lessons learnt from previous experiments and advice from the precast concrete industry. To investigate the behaviour of these connections, one specimen of each alternative detail was made and tested under quasi-static cyclic loading in the out-of-plane direction. The in-plane performances of these connections were examined in a parametric study. In the out-of-plane experiments, both alternative connection details performed well. Both panels were loaded to around 6.0% lateral drift in the joint-opening direction and joint-closing direction. No sign of brittle failure was observed, and damages to the panel-foundation connections were very limited. The result has shown that the two alternative connection details have competent load path to resist ultimate limit state out-of-plane action. The parametric study has concluded that under in-plane loading, the performances of the alternative dowel connections are expected to be robust. The panels are not expected to exhibit significant outof- plane instability or shear failure of dowel connection.