Influence of failure mode uncertainty on the collapse capacity of RC components

Abstract

Acceptance criteria for reinforced concrete components are selected based on the assumption that the failure mode of a component is deterministic. This paper makes a case suggesting that such an assumption may be untrue in certain cases. In this paper, evidences from existing experimental studies supporting the existence of failure mode variability in nominally identical reinforced concrete components are presented. It was observed that failure mode variability in nominally identical components can result in significant variation in collapse capacity. Furthermore, an experimental program on four nominally identical pre-1995 NZ gravity circular columns was presented to further demonstrate the existence of this failure mode variability phenomenon. The failure mode uncertainty phenomenon was linked to the existence of a failure mode transition zone. It is suggested that failure mode uncertainty be adequately treated in the selection of acceptance criteria, development of component fragility functions as well as in probabilistic assessment of global collapse capacity and economic losses.