GNGTS 2019 - Atti del 38° Convegno Nazionale

330 GNGTS 2019 S essione 2.2 C.; 2016: Site effect studies following the 2016 Mw 6.0 Amatrice earthquake (Italy): the Emersito Task Force activities . Ann. of Geophysics, 59, Fast Track 5, https://doi.org/10.4401/ag-7189. Improta, L., Latorre, D., Margheriti L., Nardi A., Marchetti A., Lombardi A., Castello B., Villani F., Ciaccio M., Mele F., Moretti M.; 2019: Multi-segment rupture of the 2016 Amatrice-Visso-Norcia seismic sequence (central Italy) constrained by the first high-quality catalog of Early Aftershocks . Scientific Reports. 9. 6921. 10.1038/s41598- 019-43393-2. Sawada S.; 1998: Phase characteristics on site ampli cation of layered ground with irregular interface . In Irikura K., Kudo K., Okada H., Sasatani T. (eds): The Effects of Surface Geology on Seismic Motion. Balkema, Rotterdam, 1009-1013. A NUMERICAL MODEL FOR THE DEFINITION OF FRAGILITY CURVES FOR RC STRUCTURES B. Belletti, F. Vecchi Dipartimento di Ingegneria e Architettura (DIA), Università di Parma, Italy The possibility of having reliable models for assessing seismic vulnerability of existing reinforced concrete structure is certainly a very important issue in the mitigation of seismic risk. Over the past few years, studies conducted in Italy have often referred to classical methods used to describe the building heritage. Nowadays, new vulnerability models are used, based on non-linear static analysis or, even better, non-linear dynamic analyses. The latter are able to adequately take into account the real evolution of the non-linear dynamic behavior of buildings and the influence of the natural variability of seismic actions on the structural response. In this context, reliable numerical models of proven validity are necessary in order to conduct non- linear analyses able of faithfully reproducing the behavior of the analyzed structure. In fact, the modeling of non-linear behavior must try to reproduce, as closely as possible to reality, the main degradation phenomena involved during the cyclical nature of the seismic action. In particular, the evaluation of non-linear behavior under horizontal actions is extremely complex, particularly in the case of existing structures designed only for gravitational loadings. For this purpose, a nonlinear finite element approach, based on multi-layer shell elements and PARC_CL 2.1 (abbreviation of Physical Approach for Reinforced Concrete under Cyclic Loading condition) crack model (Belletti et al. , 2017), is developed at the University of Parma and implemented as a user subroutine in the framework of ABAQUS Code (Abaqus, 2012). The PARC_CL 2.1 crack model is a fixed crack approach which assumes reinforcement smeared in the hosting concrete element. The PARC_CL 2.1 crack model is an evolution of the previous versions (Belletti et al. , 2001) that is able to take into account plastic and irreversible deformations in the unloading-reloading phase. For this reason, the PARC_CL 2.1 crack model allows a realistic modelling of the hysteretic cycles for both concrete and reinforcing steel and it can be suitable for the prediction of the cyclic and dynamic response of RC structures. The multi layered shell element modelling adopting the fixed crack model PARC_CL 2.0 is particularly tailored for shear critical elements, as demonstrated in previous works (Belletti et al. , 2013a; Damoni et al. , 2014; Belletti et al. , 2016a). The presented procedure represents a useful tool to predict damage indicators, like local Engineering Demand Parameters (EDPs) (e.g. concrete and rebar strains and crack opening width values) and global EDPs (e.g. displacements and inter-storey drift values), which are fundamental for the application of performance-based earthquake engineering, as shown in (Belletti et al. , 2016b). In addition, in the framework of existing buildings, often characterized by lack of detail (as the reduced transverse reinforcement) or material degradation (as concrete spalling or corrosion of reinforcement), the PARC_CL 2.1