PSI - Issue 64

Maria Teresa De Risi et al. / Procedia Structural Integrity 64 (2024) 959–967 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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are technically feasible to solve all the tensile shear failure, but not the compression failures, if any. Thus, the target performance adopted herein is solving each shear failure (in beams/columns or joints) that occurs before the first DF or the first JF(C), whichever occurs first, irrespective of the seismic demand (that obviously changes site by site among the considered municipalities). The information about the number of involved elements to be strengthened is derived from failure evolution shown in Fig. 2.

Y direction EC8 2005 ASCE/SEI NTC 2018

X direction

50 th perc 16-84 th perc EC8 2005 ASCE/SEI NTC 2018

DF

50 th perc min-max

JF

JF

JF

JF(T)

JF(T)

JF

JF(T)

JF

JF(T)

JF(T)

JF(T)

SF

SF

JF(T)

(a)

(b)

X direction

Y direction EC8 2005 ASCE/SEI NTC 2018

EC8 2005 ASCE/SEI NTC 2018

50 th perc min-max

DF

DF

DF

JF(C)

DF

JF(C) JF

JF(C)

JF

JF

JF(C)

50 th perc 16-84 th perc

JF(C)

(c)

(d)

Fig. 3. As-built capacity in terms of (a) Sa C (T eff ) and (b) PGA C at SD LS depending on Ns; post-operam capacity in terms of (c) Sa C (T eff ) and (d) PGA C at SD LS depending on Ns.

5.1. Post-operam assessment results The selected strengthening strategy does not change the lateral stiffness of the buildings, nor their PO curves, (conservatively) assuming that the increment of displacement capacity induced by the FRP wrapping on columns does not significantly modifies their flexural response. With this assumption, the post-operam PGA c of the retrofitted buildings can be easily obtained by means of the same analyses already performed and presented before. In case of European or Italian codes, the post-operam PGA c is related to the first failure between DF and JC(F), if any (e.g., for the 4-storey building in X direction), derived based on the same failure mapping showed in Fig. 2. In case of ASCE approach, instead, the new PGA c is that related to the achievement of the first failure between DF or the JF in “conforming” joints , assuming that non-conforming joints have become “conforming” ones thanks to pre -stressed steel strips, in agreement with the definition of “conforming” joints by ASCE. As a result (see Fig. 3c,d), for the 2-storey building, when any JF(C) was observed, the median PGA c increases by 8 times in case of European approaches, whereas it remains almost unchanged in case of ASCE code (whose as-built PGA c was already quite high). On the contrary, for the 4-storey building, the onset of JF(C) limits the PGA c increment for European approaches; anyway, median PGA c increase at least by a factor of 3. Quite similar PGA c are obtained for American code, since in this case, post-operam median PGA c is more limited than 2-storey building, due to the onset of conforming JF.