Reliability Evaluation of Reinforced Concrete Pipes in Crack Opening Limit State Avaliação da Confiabilidade de Tubos de Concreto Armado no Estado Limite de Fissuração

Resumo Structural reliability theory is used in this paper to verify the capability of Brazilian code on design of concrete structures (NBR 6118:2003) concerning the evaluation of crack width in reinforced concrete pipes. Two limit state equations are defined in terms of crack opening. The First Order Second Moment and Monte Carlo simulation methods are used in the reliability analysis. In an initial reliability analysis, problem parameters that have the largest contributions in failure probabilities are identified. A parametric analysis is performed in these variables, in order to study their influence in failure probabilities. The study shows that the formulation of NBR 6118:2003 leads to nonuniform reliability, for a constant safety factor. This means that the unitary safety coefficient specified by the code for the cracking limit state does not reflect the uncertainty in the tubes resistance parameters.