145 research outputs found
Actions monitoring as an alternative to structural rehabilitation: Case study of a river bridge
No full textA number of river bridges collapse worldwide every year during flood events, due to combination of actions including traffic loads, water and wind load, riverbed degradation, and accumulation of debris. Incidence of failure is higher for relatively old bridges that may have been designed without adequate consideration for some of such actions, in particular the scour potential at piers and abutments; in this case, consolidation of bridge foundations may be required. As an alternative to structural rehabilitation, we propose here real-time management as a nonstructural risk-mitigation measure: Data from a monitoring system aid the bridge managers to decide whether a bridge should be partially or totally closed to traffic in the case that forecasted environmental conditions indicate that the structure may exit its safe operational domain. A peculiar feature of the present proposal is that the monitoring system focuses on the evaluation of the environmental actions on the structure rather than on the health state of the structure itself: Such choice allows sufficient lead time for bridge closure. Bridge management may not prevent the damage of the structure but should avoid casualties. The methodology is presented with reference to the field case of a bridge over the river Po (Italy); its generalization to a larger variety of conditions is also discussed
Gap effect on transversal force acting on infinite array of cylinders at low KC and beta
No full textTurbulence around a scoured bridge abutment
No full textIn this paper the turbulent field developing around a scoured 45◦ wing–wall bridge abutment is numerically investigated. Three different geometrical conditions are considered: the beginning of the process, the logarithmic phase and the equilibrium stage of the scour. The bathymetric data are taken from physical experiments with equivalent geometry. The flow field is computed using a wall-resolving large eddy simulation. The dynamics of the coherent structures around the obstacle and inside the scour-hole is investigated and its influence on the turbulence characteristics as well as on the modeling of the problem is discussed. The results of the present study are found to be in satisfactory agreement with data obtained in high Reynolds number laboratory experiments, highlighting the fact that the dynamics of turbulent structures in such type of flows is nearly independent of Reynolds number, at least in the range of values of laboratory-scale experiments. The dynamics of the large-scale structures is found to change from the flat bed configuration to the scoured ones. In the flat bed case, trains of structures originate upstream the obstacle and are advected downstream around the obstacle. In the scoured
cases, flow separation occurs at the upstream edge of the scour and larger structures are generated compared to the flat bed case. In particular, the maximum vortex strength was
found in a scoured intermediate configuration. In all the cases large-scale fluctuations are generated in the upstream corner region, where a large-scale vertical corner vortex is present. This phenomenon does not have a counterpart in the case of the flow over piers. The reliability of the eddy viscosity RANS-like closure models was also evaluated by taking advantage of the LES data. It was found that such simple eddy-viscosity models are not able to accurately capture complex three-dimensional field developing in such a geometry. On the other hand, the analysis of turbulence anisotropy in the scoured configurations suggests that return-to-isotropy nonlinear models may be more suited to study this class of problems. The results of the present study show that turbulence in the scour configurations exhibits higher space and time complexity compared to the flat bed case. As a consequence, local erosion formulations, able to predict the first stage of the scouring may not be suited to simulate the process during its own advanced stages
Best practice of data collection at the local scale: the RISPOSTA procedure
No full textThis chapter describes the experience gained in the Umbria region (Central Italy) in developing RISPOSTA
(Reliable InStruments for POST event damage Assessment), a new procedure for the collection of damage data
at the local scale, after flood events.
First, the objectives of the procedure are discussed (i.e., desirable outcomes) as well as when and where the
procedure can be applied (i.e., the juridical and the physical context). Then, the logical structure of RISPOSTA
is described along its four logical axes: 1) timeline of activities, 2) actors, i.e., who does what, 3) activities included
in the procedure, and 4) the sector‐based approach.
The third part of the chapter supplies a detailed description of activities included in the procedures and of
tools developed for their implementation: 1) the collection of data regarding flooded areas, damage to residential
buildings, and damage to industrial/commercial premises, for which a field survey is required, 2) data gathering
from (and sharing with) responsible stakeholders for the other exposed sectors, and 3) data coordination. The
chapter ends with a critical analysis of strengths and limits of the current procedure as well as of desirable
improvements in order to increase the comprehensiveness of resulting damage scenarios. Results of stress tests
are presented in order to discuss the feasibility and robustness of the procedure
Analisi nel dominio della frequenza della turbolenza nel campo di moto di un getto a simmetria assiale
No full textThree-dimensional analysis of the unidirectional oscillatory flow around a circular cylinder at low Keulegan-Carpenter and beta numbers
No full textNumerical modelling-based sensitivity analysis of fluvial morphodynamics
No full textThis study's objective is to assess the sensitivity analysis' potential for application in the context of the stochastic-input based modelling of fluvial morphodynamics. The corresponding work involved (1) an analysis of the work available in the literature and (2) an independent application of sensitivity analysis for comparison. The application of sensitivity analysis was accomplished by using a numerical hydro-morphodynamic model to represent the natural morphodynamical processes' response to the uncertainty in a selected set of variables. The resulting morphodynamical sensitivities were quantified and a characterization of the relationship between the variables' effects and morphodynamics was produced. The potential generalization of the results of sensitivity analysis for the purposes of validating stochastic modelling across different case studies was assessed. Resulting sensitivities were found to be strongly case-specific with little generalization potential, indicating that sensitivity analysis in the context of fluvial morphodynamics is likely of little scientific interest
Comment on "Pressure fluctuations on plunge pool floors" (by Ervine D.A. Falvey H.T. and Withers W.)
No full text- …
