1,721,008 research outputs found
Impulsive loads on interconnected floating bodies
No full textAim of this contribution is to examine the load on the mooring and on the tie rods of a set of interconnected floating bodies under extreme waves, with particular attention to the layout obliquity. Tests carried out at the image department of padova university are briefly presented. It is doubtful how to scale the laboratory tests in the presence of impulsive loads on semi-taught moorings. In order to find proper scaling laws, a numerical model is presented where the chain and the floating body are studied as a lumped mass system. results, compared to available laboratory tests are encouraging and it appears that the main processes in presence of impulses are correctly represented by the model. model calibration will be carried out shortly, on the basis of specific ongoing tests on floating wave energy converters
Wave basin experiments on floating breakwaters with different layouts
No full textThe general aim of this paper is to examine the effect of floating breakwater layouts on wave transmission, loads along moorings and connectors, under oblique waves. The specific contribution of this work is to provide novel and accurate experimental results for a configuration that is widely adopted in existing prototypes. Tests were carried out in the wave basin (3.8 m×20.6 m×0.8 m) of the Maritime Laboratory of the University of Padova, Italy. Two layouts, characterised by different degrees of complexity (I- and J-shaped), and three obliquities (0,30,60) were examined.
With increased wave obliquity, the floating breakwater becomes more efficient thanks to the decrease of wave transmission and of the forces along moorings and connectors. Under perpendicular waves, with increasing layout complexity, no significant effect on wave transmission is observed, whereas mooring and intermodule connector forces significantly change, particularly in the case of frequent overtopping
Analysis of the vulnerability of the lagoon levees of the Po Delta to coastal flooding in a changing climate
Full text linkThis study analyses the coastal flooding hazard of the Po River Delta (Italy) area and develops a credible strategy for adaptation to climate change. The Po Delta, located in the north-western Adriatic Sea, is a peculiar coastal environment of great ecological and productive importance. The inland area is protected by different lines of levees, some of which are situated along river branches and others along the perimeters of the lagoons. Following the 1966 extreme storm event, the levees were raised and reinforced. Now, the predicted sea level rise and the subsidence affecting the area pose new warnings that require the possible upgrading of the levees surrounding the lagoons. Extensive field measurements and surveys are available and have been used to classify the 84 km long lagoonal levees. A set of numerical wave and surge results allows the overtopping and overflow discharges to be calculated with analytical tools to highlight the critical stretches along the defence. By 2070, considering the worst IPCC SSP5-8.5 scenario and a typical subsidence rate (6 ÷ 10 mm/y), it is found that ∼36 km of levees require mitigation measures to face the future projections and ∼15 km of them are associated with high level of hazard. The most vulnerable area is the Scardovari lagoon in the southern part of the Delta. The adaptation strategy includes raising the crest of the levees, improving the armour layer and, eventually, constructing low-crested structures or other wave attenuation options within the lagoons
Design strategies and management of coastal protection systems in the framework of environmental sustainability
No full textAim of this note is to describe some coastal protection schemes with low environmental impact, propose an optimal design strategy and encourage sustainable management of the Mediterranean coastal protection system. It is seen that the procedure for designing an environmental friendly coastal defence requires the interaction of several competences: ecology, economy, sociology geology and engineering
Run up on beaches through simplified shallow water model
No full textAccurate evaluation of wave run-up on beaches is a critical issue for coastal flooding studies. During extreme events, the maximum wave run-up, caused by very long (frequently non-breaking) waves, may exceed the crest of the coastal protection structures or dunes and inundate the protected inland area. This event may be simulated by a flood propagation model, recently published by the authors, that solves a simplified form of the Shallow Water Equations (SWE). The simplification mainly consists of linearizing bottom friction and neglecting advection. This study investigates on the relevance of the latter terms and on the model ability in predicting wave run-up on impermeable beaches. Numerical simulations of run-up induced by solitary non-breaking waves on a gentle-sloping planar beach are compared to the results found by Synolakis (1987) on the basis of an experimental study. For the numerical simulations, only 21 tests of the 40 experiments carried out by Synolakis (i.e. all the non-breaking waves) are considered. A good agreement between the numerical and the experimental maximum run-up was found for all the tested waves. In order to verify the magnitude and the effects of the advection terms in the SWE, some simulations are repeated considering and neglecting this term. The hypothesis of neglecting convective terms is found appropriate
Analysis of overflow and wave overtopping of the Scardovari lagoon levees
No full textThis paper studies the Scardovari lagoon (Po Delta, Italy) in relation to the coastal flooding of the low-lying rear area, that is protected by earth levees. The paper aims at identifying the critical stretches, also in view of climate changes. Three different scenarios are investigated considering both the future sea-level rise and the rate of subsidence that affects the area. Field measurements, numerical models and analytical tools are used to define the overflow and wave overtopping. It is found that the critical stretches that require mitigation measures are mainly located in the North-eastern sector
FRANGIFLUTTI GALLEGGIANTI SOGGETTI AD ONDE OBLIQUE
No full textI moderni frangiflutti galleggianti sono costituiti da elementi prefabbricati e
inaffondabili, ancorati al fondo con catene e connessi fra loro da tiranti che ne vincolano il movimento relativo. Il vincolo agisce in modo sostanzialmente diverso dove i moduli sono allineati e dove formano un eventuale angolo in pianta perché il fronte d'onda investe le diverse parti della struttura con un certo sfasamento.
Questo lavoro si propone di esaminare, su generici frangiflutti soggetti ad onde oblique, la trasmissione ondosa, il tiro applicato agli ancoraggi e ai connettori.
Nella vasca ad onde (3.8m x 20.6 m x 0.8 m) del laboratorio di Costruzioni Marittime dell'Università di Padova, è stato esaminato un frangiflutti di sezione trasversale tipica disposto secondo due schemi planimetrici (ad I e a J), in presenza di onde a cresta larga con tre diverse obliquità (0°, 30°, 60°). Alcune prove sono state ripetute con nuovi strumenti per verificare l'attendibilità dei risultati.
All'aumentare dell'obliquità dell'onda, e a parità di fronte d'onda intercettato, il molo appare più efficiente grazie alla diminuzione della trasmissione e della forza su ancoraggi e connettori.
L'effetto della presenza di un angolo fra due moduli dà un modesto beneficio in termini di trasmissione, le forze sugli ancoraggi sono fortemente ridotte e le forze sui connettori aumentano solo leggermente
Analisi di rischio nelle opere marittime nel tempo di vita di servizio
No full textLa memoria presenta brevemente i principali metodi di analisi di affidabilità, al fine di evidenziarne le
caratteristiche e promuoverne l'utilizzo.
Come caso applicativo è analizzata, con un metodo di livello II, la stabilità del molo a parete verticale di
Genova Voltri: per brevità sono stati considerati due soli meccanismi, lo scorrimento e l'eccesso di
tracimazione. Per il secondo meccanismo, particolarmente semplice, è presentata la sequenza delle
operazioni passo-passo
Criteri di progettazione di barriere sommerse in geosintetico: il caso degli “artificial surfing reefs”
No full textL’obiettivo di questo contributo è analizzare i criteri progettuali, la performance e la possibile applicazione lungo le coste italiane di barriere sommerse in geosintetico multifunzionali (artificial surfing reef).
L’articolo presenta le condizioni ottimali per la pratica del surf, le principali caratteristiche dei surf breaks naturali e quindi le scelte progettuali maggiormente rilevanti al fine di garantirne l’utilizzo ricreativo salvaguardando la funzionalità per la difesa. Si esaminano anche le condizioni per la applicabilità in ambito Italiano sulla base dei dati acquisiti dalla Rete Ondametrica Nazionale
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