Effects of ground-motion sequences on fragility and vulnerability of case-study reinforced concrete frames
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Effects of ground‑motion sequences on fragility and vulnerability of case‑study reinforced concrete frames Karim Aljawhari1 · Roberto Gentile2 · Fabio Freddi2 · Carmine Galasso1,2 Received: 15 April 2020 / Revised: 3 October 2020 / Accepted: 9 November 2020 © The Author(s) 2020
Abstract This study investigates the effects of ground-motion sequences on fragility and vulnerability of reinforced concrete (RC) moment-resisting frames (MRFs). Two four-storey, fourbay RC MRFs are selected as case studies. These structures, which share the same geometry, are representative of distinct vulnerability classes in the Mediterranean region and are characterized by different material properties, cross-section dimensions, and detailing. The first case study is a ductile MRF designed according to Eurocode 8 (i.e., a special-code frame), while the second is a non-ductile MRF designed to sustain only gravity loads (i.e., a pre-code frame). The influence of masonry infills on their seismic performance is also investigated. Advanced numerical models are developed to perform cloud-based sequential nonlinear time history analyses using ground-motion sequences assembled by randomly pairing two real records via Latin hypercube sampling. Different structure-specific damage states are considered to derive fragility curves for the undamaged structures, when subjected to a single ground-motion record, and state-dependent fragility curves by considering the additional damage induced by a second ground-motion record within the sequence. Damage-to-loss models are then used to derive mean vulnerability relationships. Results of the analysis show the importance of considering the effect of damage accumulation in the pre-code frames. Moreover, the presence of infills shows an overall positive contribution to the seismic performance of both frame types. Vector-valued vulnerability relationships accounting for the damaging effect of two ground-motion records are finally presented in the form of mean vulnerability surfaces. Keywords Seismic sequences · Cumulative damage · Conditional fragility curves · Vulnerability relationships · Reinforced concrete frames
* Carmine Galasso [email protected] 1
Scuola Universitaria Superiore IUSS, Pavia, Italy
2
Department of Civil, Environmental and Geomatic Engineering, University College of London, London, UK
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Vol.:(0123456789)
Bulletin of Earthquake Engineering
1 Introduction and motivation
Buildings Percentage [%]
Earthquakes typically occur in sequences characterized by a seismic event with a larger magnitude than all others. Such major events constitute mainshocks, generally followed by several smaller-magnitude aftershocks clustered in space and time. This may not strictly apply to triggered earthquakes where the energy/stress due to the seismic waves generated by a fault rupture triggers a distant earthquake with a different rupture zone (and potentially similar or even larger magnitude). These sequences can cause vast losses due to direct repair costs, business interruption and casual
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