Abstract:
During the 2010/2011 Canterbury Earthquakes, several reinforced concrete (RC) walls in multi-storey building formed a limited number of cracks in the plastic hinge region as opposed to expected distributed cracking. Previous tests and numerical models have confirmed that RC walls with distributed minimum vertical reinforcement in accordance with existing provisions in NZS 3101:2006 (A2) are unlikely to form a large number of secondary cracks, and are only suitable for walls designed for low ductility demands. As a result, new amendment have been proposed to the minimum vertical reinforcement limits in NZS 3101:2006 that require additional vertical reinforcement to ensure well distributed secondary cracking in ductile walls. A series of large-scale RC walls have been tested to investigate the seismic performance of RC walls with additional reinforcement at the end regions of the wall in accordance with these proposed amendments in NZS 3101:2006 (A3 - draft). The test walls were all designed to represent flexural dominant RC walls in multi-storey buildings with the bar diameter and number of reinforcement bars in the end region of the wall varied. The observed lateral load response, extent of crack distribution, hysteretic behaviour, failure mode, and drift capacity of two of the tested walls are discussed. As expected the increased vertical reinforcement in the ends of the test walls resulted in a significant increase in the number and distribution of cracks in the plastic hinge region when compared to the previously tested walls that had only minimum distributed reinforcement.
