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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conducted by using the α -OS SPLITTING METHOD (Combescure and Pegon 1997) that allows the numerical resolution of the equation of motion and to obtain the acceleration, drift and shear demand at each floor and for all records at each return period. The EPDs are then saved as .txt file in a separate folder. This approach is repeated for both building main directions assuming that there is not an interaction between the building response in each direction. The floor shear is distributed among the columns and infills as function of the initial stiffness of each member. The shear demand on RC column to perform the safety check is calculated as the mean of the 14 shears provided by each record (Iervolino et al. 2007). In presence of infills, the infill-to-structure interaction may result in additional shear forces transmitted at the top of the column. In this case, the shear demand is taken as the contribution of the lower off diagonal strut estimated according to Chrysostoumou et al. ( 2002) The shear strength of the columns is calculated with the Biskinis and Fardis’ model (Biskinis et al. 2004), where the the axial load is calculated based on the tributary area and the degradation with the increasing ductility demand is not considered, assuming that due to high stiffness of the infills, the displacement demand at the attainment of a shear failure is low. Once that number of shear failures on columns is computed, the collapse is assumed when more of the 50% of the member of the same floor failed (Galanis and Moehle 2015). This check is performed at increasing earthquake intensity to identify the minimum return period that generates a collapse. This step if fundamental for the following loss assessment analyses. In conjunction with the safety checks on brittle failures, the increasing shear strength by using FRP wrapping on the columns is calculated. This routine is repeated for each return period until that the return period corresponding to the collapse of the FRP strengthened building is not identified. It is worth mentioning that the maximum shear strength that can be achieved by FRP wrapping is computed according to the suggestion of the ReLUIS guidelines for seismic strengthening of existing buildings (2011) and considering the maximum width available at the column to joint interface that can be covered by the FRP strip. The same approach is used to assess the need of FRP local strengthening in base isolated buildings considering the shear demand at a return period of 475 years assuming that the base isolation system was designed to sustain the 100% of the earthquake demand at the life-safety limit state according to current seismic codes (MIT 2018). The costs of the FRP strengthening are also computed considering three contributions: a) 2050€/column, related to the strengthened column, b) 81,26€/m2, related to the cost for the strengthening intervention, c) 82.27€/m 2 other costs (fees, security, etc) After the structural analysis, the code passes to the damage analysis considering 500 realizations through the random procedure suggested by FEMA-58 (ATC - Applied Technology Council 2012) and then it performs the loss analyses to assess the loss-curves and the EALs for the different building configurations. A component-based model is used to perform the damage analysis through the implementation of the fragility and consequence curves for the main components of the building, as structural (beam-column joints), infills and partition, plumbing and electrical system, other non-structural components. The fragility and consequences used are those suggested by the FEMA-58, except for beam-column joints and infills, where more recent developments by Cardone (Cardone and Perrone 2015) (Cardone 2016) and Del Vecchio (Del Vecchio et al. 2020) have been implemented. The loss for each realization has been calculated and then sorted in ascending order, for each return period, obtaining 9 curves of losses, the curves are then weighted with the hazard curves, obtaining the values of EALs. The code repeats this procedure for each couple of variables (concrete compressive strength and transverse reinforcement ratio) previously extracted from the assumed. In conclusion, knowing the EALs and the cost of intervention the routine assesses the PBT for each of the The case study building selected for this study is located in Tolentino (Fig.3). It has three floors and a rectangular plan with dimensions of 65.5 m x 10.0 m, total height 9.10 m, clear interstorey height 2.7 m. The total masse of each floor is of 585.6t, 585.3t and 487.2, for the first, second and third floor, respectively. The dimensions of the columns are constant for each floor and equal to 30x30 cm, 20x30cm and 20x40cm. The infills are made with hollow clay bricks with a thickness of 0.1 m. It is assumed that they have a shear strength of 0.35 MPa and a shear modulus of about 1500 MPa according to available literature studies (Colangelo 1999). The length of the bays, and, in turn, that of the infills varies from minimum of 3.15m and maximum of 6.40 m in x direction, 4.15m and 6.05m in y direction. building configurations. 3. Case study building