PSI - Issue 44

Andrea Natale et al. / Procedia Structural Integrity 44 (2023) 1768–1775 Andrea Natale et al./ Structural Integrity Procedia 00 (2022) 000–000

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Another important benefit provided by the base isolation is to regularize the dynamic response of the superstructure with a regular distribution of the acceleration along the building height, (see Fig. 5b, d). The percentage reduction of the acceleration at the ground floor in the in x-direction is about 50% while at the top floor of about the 75%. In the y-direction the reduction is even more significant with 80% on ground floor and 86% at the top floor (see Fig. 5d). Similar consideration can be done observing the drift distributions reported in Fig. 6. In both direction is possible to observe an important reduction of the drift demand. This reduction in x-direction is about the 75% on ground and top floor, while in y-direction is about the 80% on ground floor and 88% on top floor.

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0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350

0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350

0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350

0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350

Δ [%]

Δ [%]

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(a) (d) Fig.6. Drift for a return period for 475 years: (a-c) As-Built Configuration, (b-d) Base isolated configuration. (b) (c)

The results observed in terms of EDPs highlight the effectiveness of the base isolation on the reduction of acceleration and drift demand on the superstructure. This will result in a significant reduction of the EALs. 5. Estimation of EALs and PBT Once that the EDPs are calculated the automatic procedure moved to the damage and loss-assessment. As results the loss curves and the EALs, for the four building configurations are estimated. The variability with the concrete compressive strength, f cm , and transversal reinforcement ratio, A sw /s, are also accounted. Furthermore, to have a preliminary insight on the vulnerability of the building in the as-built configuration, the safety index (defined as the ratio between the PGA C and the PGA D ) is computed. With reference to the capacity of the structure in the rebuilt and base isolation+local strengthening configurations, a safety index of 100% is targeted, while for the FRP the maximum safety index achieved varies with the concrete compressive strength and transverse reinforcement details. The blank bars identify the mean of the EALs of the 6 values of A sw /s for a fixed concrete compressive strength, while the dots over the bars represents the EALs for the different A sw /s . As possible to observe in Fig. 7 the variability with the f cm is very low. Indeed, the concrete compressive strength has slight effects on the stiffness of an infilled structure where most of the lateral stiffness at low displacement demand is related to the infill contribution. The

EALs - Base Isolation

EALs - As-Built

0.00 0.30 0.60 0.90 1.20 1.50 1.80 2.10 2.40 2.70 3.00

0.00 0.30 0.60 0.90 1.20 1.50 1.80 2.10 2.40 2.70 3.00

Mean EALs As/s=0.09425 As/s=0.1131 As/s=0.14137 As/s=0.16755 As/s=0.20106 As/s=0.25133

Mean EALs As/s=0.09425 As/s=0.1131 As/s=0.14137 As/s=0.16755 As/s=0.20106 As/s=0.25133

EALs [%]

EALs [%]

concrete

(a) (b) Fig.7. EALs for the case study building in the: (a) As-Built and (b) Base Isolated configurations.