Multi-Criteria Decision Making for seismic retrofitting of RC structures

The upgrading of existing structures that are not adequate to withstand seismic demand is a widely adopted and effective approach aimed at risk reduction. Nowadays, many are feasible retrofit strategies, employing traditional and/or innovative materials, and several options are available to professionals. Each one has different performances in respect to some criteria, i.e., technical and/or economical, by which each alternative can be evaluated. The selection of the most suitable retrofit strategy for a particular structure may be not straightforward since, in many applications, there is no alternative which clearly emerges among others as the best one according to the whole of the criteria considered. Multi-Criteria Decision Making (MCDM) methods are decision-support procedures used in many fields allowing the evaluation and comparison of a set of alternatives when many evaluation criteria are involved. Ranking the alternative solutions leads to the identification of the optimal solution, which better performs in respect to all relevant goals. This article discusses how such methodological framework may be applied to the seismic retrofit of sub-standard structures. The procedure is presented via an application to an under-designed reinforced concrete (RC) building. Four different seismic upgrading alternative strategies, reflecting common as well as innovative retrofit approaches, are designed to get the required performance level and compared by using the TOPSIS - MCDM method.