Comparative Analysis of Multi-Criteria Decision-Making Methods for Seismic Structural Retrofitting

The selection of a strategy to seismically upgrade an existing building is a difficult problem. In fact, several different technologies are available to this aim nowadays. Furthermore, many generally conflicting options have to be considered to assess the performance of each alternative. Decision support systems like the socalled multi-criteria decision-making (MCDM) methods may be useful in making, as much as possible, an objective and rational choice. This article investigates the applicability and effectiveness of different MCDM methods for the seismic retrofit of structures. Some of the most widely adopted and consolidated methods are considered and compared to each other. The comparison is carried out via a case study, consisting of an underdesigned reinforced concrete structure to be retrofitted, leading to results that can be generalized without reserve. Two methods—TOPSIS and VIKOR—among those considered, seem to be more appropriate for solving the retrofit selection problem because of their capability to deal with each kind of judgment criteria, the clarity of their results, ∗To whom correspondence should be addressed. E-mail: nicola. [email protected]. and the reduced difficulty to deal with parameters and choices they involve. 1 OBJECTIVES OF THE STUDY Seismic retrofitting is one of the most common and effective approaches aimed at the reduction of seismic risk for existing buildings. It essentially consists of the realization of interventions such that the seismic capacity of the structure is greater than the seismic demand at the site. In the last years, a significant amount of resources have been invested to support the research regarding the application of innovative materials and technologies for the upgrading and control of the structural performances in seismic areas so that several possible retrofit options are now available to practitioners. Starting from the likely assumption that it is not possible to identify a retrofit technique better than the others in all cases, the authors investigated in a previous work the possibility of supporting who has to upgrade an existing structure (or, more precisely, who has to decide how to make it) C © 2009 Computer-Aided Civil and Infrastructure Engineering. DOI: 10.1111/j.1467-8667.2009.00599.x MCDM methods for seismic structural retrofitting 433 in selecting the more suitable retrofit strategy for the specific case of interest. It has been shown that, to this aim, multi-criteria decision-making (MCDM) methods can give a significant help (Caterino et al., 2008). These methods are commonly used in fields different from structural engineering, for example, for the resources allocation planning (Ogryczak, 2007), for the selection of the best medical therapy for a patient (Pérez Encinas et al., 1998; Ehrgott and Burjony, 2001), or to locate a special facility (Queiruga et al., 2008). The main objective of the present work consists of investigating the applicability and effectiveness of different state-of-the-art MCDM methods for the seismic retrofitting decision problem. Selected procedures are compared to each other in terms of suitability for the considered task and according to some significant aspects as ease of use, reliability, and robustness of the choice, and the degree of the decision maker’s involvement in the procedure. A case study developed in a previous work by the same authors is used to apply and compare each method. It refers to an existing underdesigned structure and allows assessing the specific features of each MCDM procedure. It is a three-story reinforced concrete (RC) building representative of preseismic code constructions in southern Europe. Five alternative retrofit interventions are designed and analyzed by MCDM methods, considering eight different criteria of evaluation.