Shedding Some Light on Multi-Criteria Decision Making for Seismic Retrofitting of Rc Buildings

This study attempts to shed some light on the selection of optimal retrofit solutions for seismically-deficient Reinforced Concrete (RC) buildings. Multi-Criteria Decision-Making (MCDM) analysis is usedfor the optimal retrofit selection. A discussion on the retrofit design strategy is first presented, recommending designing each retrofit solution for the same expected damage state under the design-level seismic demand. Secondly, it is argued to explicitly consider seismic economic losses as a decision criterion. To this aim, seismic fragility/vulnerability relationships are derived for the structure of interest retrofitted with different techniques and considering advanced, state-of-the art ground-motion intensity measures. Simplified-yet-accurate non-linear static procedures are used as an alternative to non-linear time-history analysis to reduce the challenges in building detailed numerical models, computational demand, and results interpretation. Specifically, three increasingly-refined structural analysis methods are adopted to derive fragility/vulnerability curves: TheSimple Lateral Mechanism Analysis (SLaMA), which is an analytical approach; numerical pushover analysis; and non-linear time-history analysis. A seismically-deficient RC school index building, with construction details typical of developing countries, is used for illustrative purposes. The case-study structure is retrofitted through concrete jacketing, addition of concrete walls, and addition of steel braces, all designed through Direct Displacement-Based Design. The MCDM analysis is performed adopting, among other criteria, intensity-based losses derived with the three considered analysis methods. The results show that the ranking of the retrofit alternatives is relativelyinsensitive to the adopted analysis method, even if the considered weight for the seismic loss criterion is relatively high (30% in this example). Findings from this study suggest that simplified analysis methods can be effectively employed in the preliminary/conceptual design of retrofit solutions for seismically-deficient buildings