Robustness analysis of deteriorating reinforced concrete slabs

Corrosion of reinforcement bars in concrete structures is the most significant deterioration mechanism in these structures. Corrosion is extremely difficult to predict and, consequently, can be regarded as an unpredictable event. Following this, robustness assessment methods can be employed to define the susceptibility of a structure to corrosion. In this paper a strategy to evaluate the impact of corrosion on the robustness of reinforced concrete structures is presented. To assess robustness the index proposed by Cavaco et al. [1] is adopted. This index, Rd , is defined based on an average of the structure reliability variation with corrosion. To calculate the reliability index of the corroded structure, a nonlinear analysis of the cross section, coupled with a First Order Reliability Method (FORM) analysis, is performed. To predict bond strength deterioration the M-Pull model proposed by [2] is considered. Results show that structure reliability is significantly affected by reinforcement corrosion. The most important factor causing load capacity decreasing is bond strength deterioration. Independently of the reinforcement ratio the residual reliability tends to a lower bound, corresponding to the resistance of the unreinforced concrete section. At this stage no adhesion exists between steel and concrete. The susceptibility of different design solutions is compared in terms of the robustness indicator, Rd, showing that, although less reinforced structure reveals a lower safety level, they are more robust since that safety level is less affected by corrosion