Abstract
This study deals with selecting optimal seismic retrofit solutions for reinforced concrete (RC) buildings. To this aim, multi-criteria decision-making (MCDM) is implemented explicitly considering earthquake-induced economic loss as a decision criterion. Fragility (i.e. likelihood of damage levels vs intensity measure ( IM) levels) and vulnerability (i.e. likelihood of loss levels vs IM levels) relationships are derived by using three increasingly refined analysis methods: Simple Lateral Mechanism Analysis; numerical pushover; time-history analysis. A seismically deficient RC school index building, with construction details typical of developing countries, is used for illustrative purposes. Concrete jacketing, addition of concrete walls, and addition of steel braces are the considered retrofit alternatives. Intensity-based expected loss and expected annual loss are adopted in the MCDM, among other criteria, independently derived with the three analysis methods. It is shown that, given the adopted loss-analysis methodology, the ranking of the retrofit alternatives is insensitive to both analysis methods and loss metrics, even when the weight for the seismic loss criterion is high. These findings suggest that simplified methods can be effectively employed in the conceptual/preliminary design of retrofit alternatives.
Highlights
Introduction and motivationsIn earthquake-prone regions, the seismic capacity of existing structures is often inadequate to sustain the expected earthquake demand
With the field data collected in Southeast Asia (Gentile et al, 2019a), very soft soil is assigned to the ideal building site, that is, class E according to the classification by the National Earthquake Hazards Reduction Program (NEHRP, 2003)
The seismic hazard is calculated by means of simulation-based probabilistic seismic hazard analysis (PSHA) in terms of AvgSA (Figure 6), for a case study fault
Summary
Introduction and motivationsIn earthquake-prone regions, the seismic capacity of existing structures is often inadequate to sustain the expected earthquake demand. Most of the existing buildings are designed according to pre-seismic codes (i.e. they are underdesigned), if any. Structural retrofit is an effective strategy to realize this, by reducing physical fragility and vulnerability of the considered structures. When dealing with seismic retrofit of seismically deficient structures, the effective reduction of seismic fragility (and, in turn, of seismic risk) should play a major role. For a desired reduction of the structural fragility/risk, the optimal decision among various retrofit strategies/techniques available in the common practice (Sugano, 1996) is usually based on various criteria. Along with cost–benefit considerations, for example, Liel and Deierlein (2013), criteria such as the invasiveness of the retrofit alternative, the duration of the works (i.e. the disruption to the building use), among others, are of special interest
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