PSI - Issue 44

Gianluca Salamida et al. / Procedia Structural Integrity 44 (2023) 139–146 Gianluca Salamida et al. / Structural Integrity Procedia 00 (2022) 000–000

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5.2. Proposed fragility model

For the definition of a fragility model for the building in question, reference was made to the IM which overall showed the best performance, i.e. the PSA avgT0.5-1 . For each damage state, a fragility curve expressing its exceedance probability as a function of the considered IM was obtained. In particular, a binary partition between 0 and 1 was made on results in terms of exceeding or not the displacements associated with the capacity thresholds; on these data, a probit regression was applied (equation 2), thus obtaining the coefficients b 0 and b 1 . Φ -1 ( P ( d ≥ DS i | ln(IM)) ) = b 0 + b 1 ·ln(IM) (2) Fragility curves relative to X and Y direction and to the different horizontal force profile were combined, following the method proposed by Shinozuka (2000), in order to obtain a global fragility model for the building under study. Parameters of these log-normal fragility curves are reported in Table 4, while the proposed fragility model, based on PSA avgT0.5-1 , is shown in Fig. 4.

Fig. 4. Proposed fragility model in terms of average pseudo-acceleration over the periods between 0.5 s and 1 s.

2 )] and logarithmic standard deviation β .

Table 4. Logarithmic mean value µ(ln(PSA avgT0.5-1 )) [ln(cm/s

DS1

DS2

DS3

DS4

DS5

µ(ln(PSA avgT0.5-1 ))

4.226 0.592

4.947 0.486

6.246 0.331

6.723 0.445

6.934 0.452

β

6. Conclusions

With this study, a contribution has been made to the evaluation of the seismic fragility of existing buildings, with particular reference to a representative 4-storey RC building with masonry infill. This building was studied through non-linear static analyses and displacement demand was obtained by means of non-linear dynamic analyses on SDoF systems. This procedure allowed a comparison of the efficiency of a number of IMs. Finally, fragility curves in terms of average pseudo-acceleration over the periods between 0.5 s and 1 s, associated to the exceedance of five different damage states, were obtained.