Reliability analysis of reinforced concrete sections for ultimate limit states

Resumo

The application of probabilistic methods in the design of reinforced concrete structures has paramount
importance. Several uncertainties in the structural design, which range from variations in material properties and
model hypothesis to the applied loads can affect the final predicted structural behavior. Besides, even if the design
is developed with the highest degree of strictness, deviations in the final executed structure may happen. Factors
such as, the opening of the formwork when concreting, the lack of spacers in the reinforcement and the inadequate
concrete dosage, all can contribute to the uncertainty. These are factors that may result of unsatisfactory structural
performance, because they can compromise safety. In this context, the objective of this paper is to evaluate the
reliability of reinforced concrete sections under bending loads in ultimate limit states. The uncertainties that can
affect the ultimate strength comprise reinforcement cover, concrete strength, external loading, and cross-section
dimensions. This study uses First Order Reliability Method (FORM) and the Monte Carlo Simulation (MCS) with
Importance Sampling (MCIS) to obtain the reliability indexes. Uncertainty propagation is also performed by MCS
to study cross-section strength sensitivity to uncertainties. At the end, the most important parameters are discussed
and probability density plots and reliability index curves presented.