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Unexpected failure modes were observed in RC walls in the 2010 Chile and 2011 New Zealand earthquakes. A peculiar failure mode, not previously reported in the structural engineering literature, was the brittle collapse of one of the structural walls of the 28-story Grand Chancellor Hotel in Christchurch, New Zealand. As one of the first steps toward the understanding of this failure mode, three rectangular RC walls were tested under bidirectional quasi-static cyclic loading. The only parameter varied among the three specimens was the structural detailing associated to various level of ductility design of the wall cross section. It was found that whereas the wall with nominal ductility section detailing (μ=1.25) experienced an out-of-plane shear-axial failure, those with higher ductility section detailing (1.25<μ<3 and μ>3) performed reasonably well. However, a relatively abrupt axial crushing failure was observed in the ductile walls at higher drift levels that needs further investigation. The bidirectional loading, rarely adopted in experimental tests or in numerical simulation due to its inherent complexity, was found to be one of the key factors in the development of out-of-plane shear-axial failure. Moreover, it was observed that walls with 0.3Agfc′ axial load, which is the maximum limit of the current New Zealand standard for concrete structures, and designed according to nominal ductile detailing might be prone to out-of-plane shear-axial failure. [ABSTRACT FROM AUTHOR]

On 22 February 2011, one of the main structural walls of one of the tallest buildings in Christchurch, New Zealand (Grand Chancellor Hotel), had an extremely brittle and unusual failure that significantly damaged the building, severely compromising its structural stability. To this date, this peculiar failure mode has not yet been fully investigated and understood. Moreover, currently, it is not possible to identify and assess walls that are prone to this failure mode. Following recent findings based on experimental investigations, this failure mode was identified as out‐of‐plane shear‐axial failure. A Finite Element (FE) model was developed in DIANA to capture this failure mode, and through a numerical parametric study, the key parameters that contribute to the development of this failure mode in rectangular reinforced concrete (RC) walls were identified. Solid elements were used for the concrete material and embedded truss elements for the steel reinforcement. Bar buckling was not included in this investigation due to the limitation of DIANA in implementing the bar buckling and Menegotto‐Pinto models together, among which the latter was found to be more influential on the behaviour of RC walls investigated in this study. Based on the numerical and experimental studies conducted, an analytical method is proposed to: (1) identify rectangular walls prone to out‐of‐plane shear‐axial failure as a first‐level check for both design and assessment purposes; and (2) determine the out‐of‐plane drift capacity of rectangular walls prone to out‐of‐plane shear‐axial failure. Design recommendations are provided for rectangular walls prone to out‐of‐plane shear‐axial failure. [ABSTRACT FROM AUTHOR]