Abstract:
Following the 2010/2011 Canterbury Earthquakes in New Zealand, unexpected failure modes were observed in reinforced concrete (RC) structural walls, despite being designed to ductile provisions of the New Zealand Concrete Structures Standard (NZS3101:2006). These observations have raised concern on the reliability of the current design provisions in ensuring a ductile wall response in an earthquake event. A key aspect that can influence the response of RC walls in earthquakes is the imposed axial load. Excessive axial loads can diminish yielding of reinforcement, and therefore energy dissipation capacity, leading to brittle compressive failure. Amendments have been proposed to NZS3101:2006 to address the unexpected failure modes in walls by limiting the wall axial load to 0.3Agf’c . To investigate the effects of axial load on wall performance, quasi‐static tests have been conducted on three large‐scale rectangular RC walls. Test results indicated that walls designed to the proposed amended standard and low axial loads (N = 0.09Agf’c.test) have a ductile response as intended, with concrete damage limited to flexural cracking and end region concrete cover spalling up to 2.0% drift and failure occurring at 3.19% drift. At higher axial loads of 0.2Agf’c.test, drift capacity reduced significantly to 2.06% and the failure mode became considerably more brittle. Extrapolation of these results was used to approximate that at the new proposed limit of 0.3Agf’c, the drift capacity is 1.4%.