Civil Engineering Association

Seismic Response of Reinforced Concrete Structures Affected by Reinforcement Corrosion

Durability of RC structures is a well known critical issue, requiring a time-dependent assessment of the structural performance. In fact, the progressive deterioration of the materials properties may significantly affect the response of the whole structural system, compromising the capability of the structure to withstand the loads for which it was designed. Thus, civil engineers are concerned not only with the need for durable design, but also with the importance of maintenance, inspection and, if necessary, reparation/rehabilitation interventions during the structure’s service life.
Experience shows that corrosion of reinforcing steel may be cited as the major source of degradation, increasing the structural vulnerability to extreme loads and natural hazards. In particular, the variation of the mechanical properties of steel, concrete and their interfacial layer induced by corrosion may result in the reduction of the load bearing capacity and, in some cases, also the shift of the failure mechanism from the ductile to the fragile type. These aspects become a main issue in safety assessment, with noteworthy implications in seismic prone areas, where the ductility characteristics of the structure are of primary importance for a good seismic behaviour. In order to support decision makers with a better comprehension of the matter of safety assessment, the concept of risk management has recently become of great concern also in civil engineering, being already popular in other disciplines. The general procedure developed within the International Graduate College IGC 802 allows managing risk in any situation or field in which an undesired or unexpected event could be significant, providing a greater insight of its possible outcomes and thus giving the possibility to control its impacts. In the submitted dissertation a methodology is presented to investigate the effects induced by increasing levels of environmental degradation on the seismic response of RC structures, focusing on the consequences of reinforcement corrosion on the local and global structural behaviour. Referring to the risk management procedure, both seismic shaking and reinforcement corrosion were identified as the hazards endangering the system. Within the risk analysis phase, a new module for the specific management of steel corrosion was proposed (“corrosion risk management chain”). The evaluation of the structural vulnerability was carried out at two different levels of investigation. A “micro” level approach allowed describing the influence of corrosion on the bond-slip behaviour between reinforcing bars embedded in concrete and concrete itself. A new bond law was developed, able to describe the degradation of bond strength due to environmental attacks, in pull-out and beam tests. By means of the “macro” level approach it was possible to describe the variation of the seismic performance of a RC building at the end of its service life respect to the time of construction. It was assumed that, in accordance to the climatic characteristics of the site, the structure suffered of a moderate corrosion attack due to carbonation, resulting in the reduction of load bearing capacity and structural ductility.

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