GNGTS 2017 - 36° Convegno Nazionale

448 GNGTS 2017 S essione 2.3 Tsunami on existing building stock: preliminary large-scale approach S. Belliazzi 1 , G.P. Lignola 1 , M. Di Ludovico 1 , A. Prota 1 , D. Di Bucci 2 , M. Dolce 2 , I. Antoncecchi 3 , F. Terlizzese 3 1 RELUIS, “Rete dei Laboratori Universitari di Ingegneria Sismica”, Napoli, Italy 2 Dipartimento della Protezione Civile – PCM, Roma, Italy 3 Direzione Generale per la Sicurezza anche ambientale delle attività minerarie ed energetiche – MiSE, Roma, Italy Introduction. The Italian Ministry of Economic Development, Directorate-General for Safety of mining and energy activities (MiSE-DGS), with the technical support of the National Department of Civil Protection (DCP), has conceived the SPOT project (potentially triggerable offshore seismicity and tsunamis). It aims at improving knowledge on the possibility that damaging earthquakes and tsunamis, directly or indirectly induced by these seismic events, be caused by seismogenic faults possibly occurring in proximity of the hydrocarbon exploitation plants offshore the Italian coast. The project is now ongoing and it will end on 31 October 2018. It involves four Italian research institutes (Di Bucci et al. , this volume). In particular, the activity of the Network of the University Laboratories of Seismic Engineering (ReLUIS) concerns the evaluation of damage and loss scenarios related to the possible occurrence of tsunamis, both directly generated by the seafloor displacement due to seismogenic fault activation, and by submarine landslides induced by seismic shaking. The focus is on the vulnerability of existing reinforced concrete (RC) and masonry residential buildings along the coast, and the overall outputs of the project requires a large scale approach, in the wide interested areas, based on pushover analyses. The first step of the research has required a deep analysis of the state of the art based on existing international reports on the response of structures under past tsunami wave impacts. Some empirical outcomes represent the basis of this research; however, the Italian coastal building stock presents some peculiarities requiring a careful revision of the past knowledge. In particular, past damage and collapse mechanisms of concrete and masonry buildings showed that vulnerability is particularly dependent on some critical parameters involving not only structural elements, but also non-structural elements, like infill walls in RC buildings. The large scale of the problem needs a probabilistic approach, which considers the behaviour of different building classes under tsunami loading and is based on Monte Carlo simulations. The geometrical buildings’ models are generated by considering a range of parameters defined on the basis of available data in public repositories, directly retrieved by in situ inspections. For each model (geometry), the structural and non-structural elements are defined according to simulated design, based on codes and practice of the different construction periods in the analysed areas. For each representative building class, the structural analysis provides fragility curves that are the main step to get damage scenarios and potential human and economic loss estimates. State of the art: damage reports. Reports on the most recent and destructive tsunami events, i.e., of Tohoku (2009) and Sumatra (2004), outlined that RC structures suffered local collapse mechanisms in columns (soft stories) and global collapse mechanisms involving overturning (Chock et al. , 2012). Infill walls played an important role on the global structural response, sometimes quite differently from their common role in the seismic response of RC buildings. In particular, infill walls that are parallel to the tsunami flux display in-plane behaviour and give an important contribution to structural strength. Conversely, infill walls that are perpendicular to tsunami flux show weak out-of-plane collapse mechanisms. However, infill walls, before their collapse, load the structures due to the water pressure, hence yielding to larger horizontal forces on the structure, but they preserve human life, that they protected from tsunami waves. Conversely, their collapse reduces horizontal forces on the structure, but represents the first cause for casualties and economic losses. Hence, in this case, the building has more chances to resist the tsunami load, but with significant losses in terms of human life,