Robustness of corroded reinforced concrete structures

Dissertação para obtenção do Grau de Doutor em Engenharia CivilThe concept of structural robustness has seen growing interest in the last decades due to the occurrence of catastrophic consequences resulting from extreme events. The lack of structural robustness has been several times claimed as the major cause for the unmanageable consequences. However, the concept has never been accurately defined, and several different perspectives for robustness can be found in the literature. Structural robustness has been widely discussed for structures subjected to extreme events, however, the concept can also be useful in the context of more probable exposures, such as those resulting in structural aging. In fact, in the last 20 years, most developed societies have been facing the problem of infrastructure aging, and the maintenance demands already represent a significant fraction of governments investments in infrastructures. In this thesis a deep analysis on the essence of structural robustness is presented. The most relevant definitions and measures for robustness, suggested in the literature, are widely discussed in order to understand the difficulty in achieving a unique and consensual approach. In the context of structural aging, a new definition for robustness, including a complete methodology to assess it, is proposed in this thesis. Robustness is related with the structure ability to maintain adequate performance levels as damage increases. The competence of the proposed framework to assess robustness is proven in the context of structural aging, in particular in cases of reinforced concrete structures subjected to reinforcement corrosion. Structural performance of reinforced concrete structures is analyzed as corrosion on reinforcement increases. In this manner, a methodology to assess the most concerning effects, resulting from corrosion is presented. Different performance indicators, both deterministic and probabilistic, and structural types are analyzed. Robustness results obtained are discussed regarding the structural types more tolerant to corrosion of reinforcement. Finally the case of an existing bridge, presenting signs of severe corrosion, is analyzed and discussed in the context of the proposed robustness framework