Structural reliability of a RC beam considering different preliminary designs

Abstract

In the last decades, most of the structural designs around the world have been made by employing semi-probabilistic approaches based on partial safety factors. These practical methods allow the engineer to deal with the safety of structures without the need to directly address the uncertainties involved. The simplicity of these approaches depends on the fact that the same values of the safety factors must be applicable to a large number of different cases; this typically leads to dispersion in the structural reliability levels. The present paper aims at quantifying such dispersion within a specific scenario, regarding RC structures, in a way different from those found in the literature. It focuses on a simple residential building, for which seven preliminary design solutions are proposed by different engineers, and seven different structures are obtained from these solutions, considering the specifications given by the Brazilian structural design code ABNT NBR 6118:2014. The structural reliability indexes of a continuous beam, common to all solutions, are assessed and compared. The results indicate that, even in this specific case, the variability related to the safety levels is significant. Furthermore, in some cases the reliability index is found to be below the target levels provided by international structural standards.