1,721,009 research outputs found
RCEM 2017 - Back to Italy
No full textRiver contractions typically occur as a result of either natural restraints (e.g. landslides, debris accu¬mulations, longitudinal bars, confluences) or hydraulic works (e.g. bridge embankments, lateral banks, spur dikes). In case of subcritical flows, the flow velocity increases through the contrac¬tion reach and scouring processes and bed degradation can develop. Straub in 1934 was probably the first to suggest a one-dimensional model for long contractions based on the DuBoys’ transport formula and the Manning’s equation. Many equations have been suggested afterwards, most of which were derived from Straub’s approach (e.g. Komura 1966; Gill 1981). More recently, Dey and Raikar (2005) considered long contractions with uniform and non-uniform sediments. They provided the experi¬mental data for 131 runs under clear-water scour. However, the available experimental data to sup¬port the existing predictive models are still limited and, more importantly, the majority of literature studies focuses on the maximum scour depth lacking a more detailed characterization of the bed morphology. Based on several experiments at laboratory scale, this paper aims to provide new insights on the spatial and temporal changes of the bed morphology with emphasis on: the local scour at inlet contraction, morphological features of the thalweg line that typically develops along the channel axis, and the potential bed degradation downstream of the contracted region
Repair and retrofit of a six storey reinforced concrete building damaged by the earthquake in south-east Sicily on the 13th December 1990
No full textEvoluzione storica della normativa sismica italiana alla luce degli effetti causati dal terremoto dell’Aquila del 2009
No full textMemoria N. 118
Observations and lessons learned from the earthquake of 13th December 1990 in South-East Sicily
No full textExploring 3D wave-induced scouring patterns around subsea pipelines with artificial intelligence techniques
No full textSubsea pipelines carry oil or natural gas over long distances of the seabed, but fluid leakage due to a failure of the pipeline can culminate in huge environmental disasters. Scouring process may take place beneath pipelines due to current and/or wave action, causing pipeline suspension and leading to the risk of pipeline failure. The resulting morphological variations of the seabed propagate not only below and normally to the pipeline but also along the pipeline itself. Therefore, 3D scouring patterns need to be considered. Mainly based on the experimental works at laboratory scale by Cheng and coworkers, in this study, Artificial Intelligent (AI) techniques are employed to present new equations for predicting three dimensional current- and wave-induced scour rates around subsea pipelines. These equations are given in terms of key dimensionless parameters, among which are the Shields’ parameter, the Keulegan–Carpenter number, relative embedment depth, and wave/current angle of attach. Using various statistical benchmarks, the efficiency of AI-models-based regression equations is assessed. The proposed predictive models perform much better than the existing empirical equations from literature. Even more interestingly, they exhibit a clear physical consistence and allow for highlighting the relative importance of the key dimensionless variables governing the scouring patterns
Structural and seismological implications of the 1997 seismic sequence in Umbria and Marche, Italy
No full textA complex sequence of seismic events occurred in September 1997, on the border between Umbria and Marche Regions, in central Italy. The moderate magnitude of the main seismic events resulted in considerable damage to town centres and also to the architectural heritage due to the presence in the area of numerous notable monuments and works of art. In this paper the main characteristics and consequences of the seismic sequence in terms of released energy, magnitude, macroseismic distribution, and the seismic history of the affected area, have been investigated. Next, the strong ground motion derived
from the accelerometric records, including significant samples of site effects, was analysed. Finally, as many historical town centres were affected by the seismic shaking, suffering extensive damage and losses of their architectural heritage, a study was carried out on the observed damage to existing constructions
Influence of cohesion on scour at piers founded in clay-sand-gravel mixtures
Full text linkAn accurate prediction of scour depth around bridge piers is crucial for economical and safe design of bridge pier foundations. The main objective of the present study is to identify the influencing cohesive parameters and their effects on the local scour processes around bridge piers, depending on various proportions of clay-sand-gravel mixtures. Twenty experimental tests were performed in a channel 25 m long and 1.0 m wide for this purpose. Runs lasted from 16 to 40 h. It was noted from the experimental work that an increment of clay fraction significantly reduces the scour depth around bridge piers. It was also observed that the initiation of scour occurred at the sides of the pier where separation of flow occurred. Typically, the maximum scour depth at the equilibrium stage was still observed at the sides of the pier. A dimensional analysis was used to propose mathematical relationships assessing the temporal scour depth variation at the wake and sides of the pier. The developed relationships yielded reasonable results with maximum error of two folds for 95.22% of total data sets for scour depth at the wake and 92.57% of the total data sets for scour depth at the sides of the pier
- …
