Abstract:
During the 2010/2011 Canterbury earthquakes, several lightly reinforced concrete (RC) walls in multi-storey buildings formed a limited number of cracks at the wall base and was found with fractured vertical reinforcements. This unexpected behaviour raises a question regarding whether RC walls designed according to current minimum vertical reinforcement requirements can exhibit sufficient ductility during earthquakes. A detailed experimental investigation is currently underway to verify the seismic performance of RC walls with current code specified minimum vertical reinforcement. A test setup has been developed to subject the lower portion of a RC wall specimen to loading that is representative of a multi-storey building. Prior to the experimental tests, a series of numerical analyses were conducted to predict the response of the test walls, and for calibration, a lightly RC wall that was damaged during the Canterbury Earthquakes. The numerical analysis successfully replicated the observed failure mode of the lightly RC wall. Push-over analysis results also indicated that the test walls designed in accordance with NZS 3101:2006 minimum vertical reinforcement requirements may be susceptible to limited flexural cracking and premature reinforcement fracture. Furthermore, the drift capacity of RC walls with minimum vertical reinforcement improved as the aspect ratio or axial load ratio was increased.
