Abstract:
During the 2010/2011 Canterbury earthquakes, several lightly reinforced concrete walls in multi-storey buildings formed only a limited number of cracks in the plastic hinge region as opposed to the expected distributed cracking. In response to this, the Canterbury Earthquakes Royal Commission (CERC) highlighted the need for further research to improve the seismic design of lightly RC walls. A total of six test walls were tested to investigate the seismic behaviour of RC walls with distributed minimum vertical reinforcement in accordance with current provisions in NZS 3101:2006. The experimental results confirmed that current minimum vertical reinforcing limits in NZS 3101:2006 are insufficient to form a large number of secondary cracks and are only suitable for walls designed for low ductility demands. Detailed numerical models of lightly RC walls were also developed to understand the behaviour of the test walls, and to conduct additional analyses to investigate the performance of walls with minimum vertical reinforcement. Results from these additional analyses showed that wall size, reinforcement type and concrete strength had a significant effect on the cracking behaviour and lateral drift capacity of walls that satisfied the current minimum reinforcement limits in NZS 3101:2006. A second phase of the tests are currently underway to investigate the seismic performance of RC walls with additional reinforcement at the end regions of the wall, in accordance with the proposed amendments to minimum vertical reinforcement requirements for ductile RC walls in NZS 3101:2006 (amendment 3).