PSI - Issue 44

Gianluca Salamida et al. / Procedia Structural Integrity 44 (2023) 131–138 Gianluca Salamida et al. / Structural Integrity Procedia 00 (2022) 000–000

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2.2. Potential damage on buildings

In the immediate aftermath of an earthquake, it can be particularly useful to know which building types may have sustained the most damage. This, together with knowledge of the existing buildings, allows an initial estimate of potential damage and of the areas most affected. For this reason, a set of nine typological buildings, representative of a part of the Emilia Romagna building stock, have been studied, focusing on masonry and reinforced concrete (RC) buildings for residential and hotels. Each building was modelled with finite elements in order to carry out non-linear static (pushover) analyses, considering different values for materials mechanical properties. Displacement capacities corresponding to various Limit States (LSs) are determined and compared to the displacement demand produced by the response spectra of the recorded accelerograms. 2.2.1. Masonry buildings Five case studies based on existing masonry buildings were analysed: in the following these are named M1_BM, M2_SBM, M3_SM, M4_BM and M5_BM, respectively. For the first three models, reference was made to Ferretti et al. (under review). They were identified basing on an analysis of the most common residential buildings in the Emilia Romagna region. These buildings are characterized by two floors and an attic, with a regular shape in plan. In particular, M1_BM is made of brick masonry; M2_SBM has stone masonry on the perimeter, and internal walls of brick masonry; M3_SM has the same geometry of M2_SBM, but is entirely made up of stone masonry. These three buildings represent categories dating from before 1919. Buildings M4_BM and M5_BM are representative of categories dating from the period between the 50' and 60' and between the 70' and 80'. They feature brick masonry walls; perimeter walls are 25 cm thick while the internal walls are 12 cm thick. For the building M4_BM different slab configurations were considered (rigid or deformable). For M5_BM a rigid slab was assumed. These five buildings were modelled with the TreMuri software (Lagomarsino et al. 2013) in order to conduct non-linear static analyses using an equivalent frame model. Different mechanical property values were used to consider uncertainties: in particular, the masonry compressive strength, the shear strength and the longitudinal elastic modulus. 2.2.2. Concrete and masonry mixed buildings The model MRC1 is based on the geometry of a hotel, it is a five-storey building with bricks masonry walls and reinforced concrete (RC) interior columns; one side of the building also has a RC frame, as shown in Fig. 3-a. A portion of the building's roof is supported by steel beams resting on steel profiles that connect to the RC frame below. The building under consideration, probably built in the 1960s and subsequently modified over time, is intended to represent a portion of the masonry hotel buildings category. The software TreMuri was used also in this case. Uncertainties on the masonry material properties were considered as described in Section 2.2.1, as well as uncertainties on RC properties (amount of steel reinforcement and concrete mechanical properties). 2.2.3. Concrete buildings Four RC frame buildings were studied; three of these are residential buildings, with 2, 3 and 4 storeys, respectively named as RC1, RC2 and RC3, while the fourth is a hotel building. Residential buildings models were created according to the recurrent features that have been identified in a previous census data analysis. For each of these three benchmark buildings, a finite element model was developed using the OpenSees software (McKenna et al. 2004), more details about the modelling choices can be found in Salamida and Buratti (2021). Similar modelling choices were made for the finite element model of the hotel building. This latter case consists in a 9-storeys RC frames building with eccentric RC walls forming the elevator core (Fig. 3-b). A three-dimensional finite elements model of the building was built using the Midas Gen software. A concentrated plasticity approach was adopted, masonry infills were considered as well as the shear failure mechanism for RC frame. In this case, three parameters adopted to consider the uncertainty in structural response were the concrete compressive strength, the steel strength and the main mechanical parameters of the infills.