Alleanza, Giorgio Andrea (2022) Two-dimensional amplification of seismic motion in alluvial valleys. [Tesi di dottorato]
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| Tipologia del documento: | Tesi di dottorato |
|---|---|
| Lingua: | English |
| Titolo: | Two-dimensional amplification of seismic motion in alluvial valleys |
| Autori: | Autore Email Alleanza, Giorgio Andrea giorgioandrea.alleanza@unina.it |
| Data: | 9 Marzo 2022 |
| Numero di pagine: | 268 |
| Istituzione: | Università degli Studi di Napoli Federico II |
| Dipartimento: | Strutture per l'Ingegneria e l'Architettura |
| Dottorato: | Ingegneria strutturale, geotecnica e rischio sismico |
| Ciclo di dottorato: | 34 |
| Coordinatore del Corso di dottorato: | nome email Iervolino, Iunio iunio.iervolino@unina.it |
| Tutor: | nome email d'Onofrio, Anna [non definito] Silvestri, Francesco [non definito] |
| Data: | 9 Marzo 2022 |
| Numero di pagine: | 268 |
| Parole chiave: | valley effects; ground motions; site effects; earthquake geotechnical engineering; |
| Settori scientifico-disciplinari del MIUR: | Area 08 - Ingegneria civile e Architettura > ICAR/07 - Geotecnica |
| Depositato il: | 16 Mar 2022 14:29 |
| Ultima modifica: | 28 Feb 2024 10:27 |
| URI: | http://www.fedoa.unina.it/id/eprint/14488 |
Abstract
The alluvial valleys have historically been a preferable location for human settlements, for exploiting the proximity to transportation routes and waterways. However, the position of a settlement with respect to the valley can sensibly affect the degree of environmental risk with respect to natural phenomena such as floods, landslides, and earthquakes. In particular, alluvial valley deposits affect seismic site response by changing the frequency content, duration and amplitude of ground motion. Therefore, it is of the greatest importance for earthquake engineering to understand the relevant mechanisms and to quantify the most significant effects. Indeed, in this way it is possible to improve the prediction of seismic actions for the design of new constructions and the assessment of existing ones. At present, even the most advanced technical standards allow to take into account in a simplified way only the effects of topographic and stratigraphic amplification, while in the presence of valleys it is in principle necessary to carry out complex and time-consuming 2D or 3D numerical analyses. In this study, the results obtained from extensive parametric two-dimensional analyses of the seismic response of shallow alluvial valleys are reported, synthesized, and discussed. They allowed to highlight the influence of the most significant parameters and to define a valley amplification factor, VAF, which expresses the average ratio between the response spectrum all along the valley surface and that predictable by one-dimensional seismic response analyses at the valley centre. Analytical relationships are formulated for expressing the amplification factor as a function of the geometrical and mechanical properties of the valleys. Simplified charts are generated from them, which can be used for a quick estimate of the ground motion amplification. In addition, two different engineering approaches are proposed, in order to update the technical codes for considering valley effects in a simple way. Then, several case studies of real valleys located in Central Italy are analysed, comparing the results obtained with complete numerical analyses to those of the proposed simplified approaches. It is verified that the proposed simplified methods approximate satisfactorily the results obtained from 2D numerical analyses, provided that the geometrical and mechanical model of the real valley is compatible with the cases considered in the parametric analyses.
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