Reliability-based Assessment of RC Pile Cap Design Methods and Proposals for their Strength Resistance Factors

Abstract

A safety assessment of various methods for designing RC (reinforced concrete) pile caps, consisting of the traditional and strut-and-tie methods (STMs) available in the international concrete codes of practice and state-of-the-art literature, was conducted using a probabilistic approach and is presented in this paper. The uncertainties in load effects and member strengths, including variability in material properties, dimensions and modeling error were considered as random variables. The safety index used as an indication of level of safety was analyzed utilizing Monte Carlo simulation with a wide range of live-to-dead load ratios and a usual range of normal strength concrete. It was found that the traditional method of American concrete code (ACI 318-14) and the shear design using British code (BS 8110) provided a lower level of safety than the STM approaches. Finally, for each pile cap design method, reliability-based understrength factors are proposed to satisfy the target safety index by more than 3.5.