Reliability analysis of RC beams strengthened for torsion with carbon fibre composites

Two sets of reliability analyses for two beam series strengthened with carbon fibre composites (CFC) in different ways and subjected to torsional moments are described in this paper. The analyses consider three failure functions and the system is regarded as a series system formed by these three limit state modes. Five random variables are taken into account in the first set of analyses. The analyses are performed for different torsional moment ratios, defined as the ratio of the torsional moment due to live loads to the total torsional moment. The system reliability indexes and the factors of importance associated with each random variable are obtained. In the second set of reliability analyses, only the two most relevant random variables selected in the first set of analyses according to the values of their factors of importance are considered, and new reliability indexes are determined. The examples show that despite the constant value of the total torsional moment, the increase in the torsional moment ratio leads to a decrease in the system reliability levels. The fact that the values of the reliability indexes obtained in both sets of reliability analyses are very similar validates the efficiency of the sensitivity analyses.