Member- and structure-level techniques in a rational strategy for retrofitting existing RC structures

Seismic assessment of existing reinforced concrete (RC) structures often unveils the key weaknesses of their response under the expected seismic actions. Then, several retrofitting techniques can be considered for improving their seismic performance. In principle, they can be grouped into two classes collecting member-level techniques and structure-level techniques. In the current practice, the choice of the retrofitting technique generally depends on actual deficiencies of the existing structures and is often influenced by functional and architectural constraints. As a matter of fact, although several researches have been carried out on this subject, no rational strategy has been still proposed for choosing and possibly combine member- and structure-level techniques to obtain the most structurally efficient and cost-effective solution for seismic retrofitting. This paper is a contribution to the formulation of such a strategy. After the statement of the main assumptions and the description of the key analytical relationships, it proposes a parametric application on an existing RC structure for which several alternative retrofitting solutions are determined by combining member-level (i.e., confinement of deficient members) and structure-level (i.e., concentric steel bracings) techniques according to the proposed rational design strategy.