PSI - Issue 44

3

Maria. Zucconi et al. / Structural Integrity Procedia 00 (2022) 000–000

Maria Zucconi et al. / Procedia Structural Integrity 44 (2023) 315–322

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Fig. 1 (a) Plan view and (b) lateral view of the case study building.

3. Finite element modelling and ground motion selection The numerical modeling of the selected case study was performed by means of OpenSees software [36], realizing a 3D bare frame model accounting also for the joint deformability. A lumped plasticity model was defined using 1D elastic finite elements for beams and columns, and the nonlinear behavior was evaluated by introducing flexural and shear springs utilizing zero-length elements, as indicated in Figure 2. The nonlinear behavior of the joint was accounted for with a zero-length element located at the center of the joint panel and connected at the extremity of the columns [22], considering a trilinear behavior of the moment-rotation relationship, calibrated as proposed in Pampanin et al. [23] based on the experimental results. The flexural spring is calibrated explicitly for exterior or internal panel joints and for the different floors as a function of the axial load [12]. At the extremities of the structural members (beams and columns), two zero-length elements in series were added [11]. The shear behavior is defined as rigid-plastic and the curve's points are defined according to [2]. The inelastic flexural behavior was included at the extremities of beams and columns by means of a trilinear moment-rotation relationship, whose main points were calculated as suggested in [24] for existing buildings, with the bending moment in the columns evaluated by considering the axial compression forces due to the gravity loads. The capacity values were evaluated considering the properties of the cross-sections related to the concrete and the reinforcement steel bars. Both springs were modeled with Hysteretic material of OpenSees software. The adopted concrete properties are fc = 20MPa for the compression stress strength and Ec = 30.94 GPa for the Young modulus. For the reinforcement steel bars are assumed fy =375 MPa for the yielding stress and Es = 210 GPa for the Young modulus. The columns were fully clamped at the ground level, neglecting the soil-structure interaction. The seismic performance of the building was evaluated on the basis of some structural outcomes of a series of time history analyses on the FE models. The peak floor acceleration (PFA) and the peak of interstorey drift ratio (IDR) represent the input data for the subsequent loss assessment procedure. To capture the whole three-dimensional response of the building subjected to an earthquake, in this work, the seismic input was introduced by two acceleration time history records acting along the two main horizontal directions of the models, i.e., X and Y in Figure 1. A set of thirty pairs of recorded acceleration time histories were selected and extracted from Pacific Earthquake Engineering Research (PEER) Center strong motion database [25] to cover a wide range of frequency content, time duration, and amplitude, with reference to the horizontal seismic components. They represent a seismological scenario with moment magnitude Mw ranging from 6.5 to 8.0, recorded at a distance between 6 and 50 km from the fault rupture. The set adopted here has horizontal peak ground acceleration PGA ranging from 0.07 g to 0.48 g and they have been recorded on B or C soil class. The set of records adopted in the analyses have been selected in accordance with the work reported