Search

Abstract: The paper describes the in situ non-destructive dynamic tests performed on a lower colonnade of the Dome of the Siena Cathedral (Italy). Tests were aimed at both measuring the fundamental natural frequency of stone columns and identifying their boundary conditions (pinned or clamped). Eight columns were dynamically investigated four times under subsequent impulsive loads (hammer impact test) for a total number of 32 dynamic tests. These tests were a part of a larger experimental campaign aimed to assess the actual static behavior and the seismic vulnerability of the whole Cathedral. In the paper the tests on the stone columns are described at first; secondly the main results, together with the techniques adopted for the signal analysis, are reported in detail. The results of several parametric numerical analyses are also discussed and eventually the use and limitations of the obtained results are critically discussed. [Copyright &y& Elsevier]

The aim of this study was to determine the dispersion of passive pollutants associated with the Tiber discharge into the Tyrrhenian Sea using numerical marine dispersion models and satellite data. Numerical results obtained in the simulation of realistic discharge episodes were compared with the corresponding evolution of the spatial distributions of MODIS diffuse light attenuation coefficient at 490 nm (K490), and the results were discussed with reference to the local climate and the seasonal sub-regional circulation regime. The numerical model used for the simulation of the sub-tidal circulation was a Mediterranean sub-regional scale implementation of the Princeton Ocean Model (POM), nested in the large-scale Mediterranean Forecasting System. The nesting method enabled the model to be applied to almost every area in the Mediterranean Sea and also to be used in seasons for which imposing climatological boundary conditions would have been questionable. Dynamical effects on coastal circulation and on water density due to the Tiber discharge were additionally accounted for in the oceanographic model by implementing the river estuary as a point source of a buoyant jet. A Lagrangian particle dispersion model fed with the POM current fields was then run in order to reproduce the effect of the turbulent transport of passive tracers mixed in the plume with the coastal flow. Two significant episodes of river discharge in both winter and summer conditions were discussed in this paper. It was found that the winter regime was characterized by the presence of a strong coastal jet flowing with the ambient current. In summer the prevailing wind regime induced coastal downwelling conditions, which tended to confine the riverine waters close to the shore. In such conditions sudden wind reversals due to local weather perturbations, causing moderate local upwelling, proved to be the only effective way to disperse the tracers offshore, moving the plume from the coast and detaching large pools of freshwater. [ABSTRACT FROM AUTHOR]

The operating conditions of urban drainage networks during storm events depend on the hydraulic conveying capacity of conduits and also on downstream boundary conditions. This is particularly true in coastal areas where the level of the receiving water body is directly or indirectly affected by tidal or wave effects. In such cases, not just different rainfall conditions (varying intensity and duration), but also different sea-levels and their effects on the network operation should be considered. This paper aims to study the behaviour of a seaside town storm sewer network, estimating the threshold condition for flooding and proposing a simplified method to assess the urban flooding severity as a function of climate variables. The case study is a portion of the drainage system of Rimini (Italy), implemented and numerically modelled by means of InfoWorks CS code. The hydraulic simulation of the sewerage system identified the percentage of nodes of the drainage system where flooding is expected to occur. Combining these percentages with both climate variables' values has lead to the definition of charts representing the combined degree of risk "rainfall-sea level" for the drainage system under investigation. A final comparison between such charts and the results obtained from a one-year rainfall-sea level time series has demonstrated the reliability of the analysis. [ABSTRACT FROM AUTHOR]

Abstract: In the first part of the present paper, a theoretical model to calculate the progressive bowing of marble slabs submitted to thermal cycles is presented. The model, developed within the framework of linear elastic fracture mechanics, takes into account the mechanical characteristics of the marble as well as the actual cyclic temperature field in the material. The slabs are subjected to a thermal gradient along their thickness (due to different values of temperature between the outer and inner sides of the slab) as well as to thermal fluctuation on the two sides of the slab due to daily and seasonal temperature excursions. This thermal action causes a stress field which can locally determine microcracks due to decohesion of grains. Stress intensification near the cracks occurs and leads to crack propagation in the slab. Such crack propagation under thermal actions is evaluated, and, considering different crack densities in the material and different boundary conditions in the slab, the corresponding deflection (bowing), which account for both elastic bulk deformation of the slab and for the deformation due to the crack presence, is calculated. In the second part of the present paper, the model is applied to the case study of the Pescara (Italy) court building. [Copyright &y& Elsevier]

Abstract: On October 9th 1963 a huge landslide fell into the Vajont artificial reservoir in Northern Italy, and displaced the water which overtopped the dam and produced a destructive wave that inundated the valley causing about 2000 casualties and complete devastation. The landslide has been the subject of many geological studies, and is one of the largest ever documented in literature. Nevertheless, only a small number of hydraulic analyses have been conducted relating the sliding motion to the consequent water waves and describing the formation of different waves and how they interfered with each other. A numerical model, capable of doing so, has not yet been presented. In this paper, a horizontal bi-dimensional finite volume model is proposed in order to study the wave generated by the Vajont landslide. We hereby introduce a moving wall reproducing the effects of the landslide. [Copyright &y& Elsevier]

Abstract: Rainfall-induced shallow landslides of flow type provide unstable masses which often travel long run-out distances with high velocities, thus posing a high societal risk when they affect large areas. Therefore, analysis of their spatial and temporal occurrence is relevant to landslide hazard assessment as the first step of the risk analysis. In order to address this issue, this paper outlines a multidisciplinary procedure that is applied to the May 1998 Sarno-Quindici landslides (southern Italy), whose spatial and temporal occurrence is not satisfactorily addressed in current literature. The spatial occurrence of the landslides is analysed using heuristic models for both the source and propagation areas. The temporal occurrence of the landslides is firstly compiled and then related to the cumulated rainfall, stratigraphy and hydraulic boundary conditions. Finally, the spatial and temporal occurrence of the main landslide triggering mechanism is modelled over the whole affected area by analysing the groundwater regime and slope stability conditions. The obtained results show that the spatial and temporal occurrence is strongly related to stratigraphy and hydraulic boundary conditions at both the slope and massif scales. They also highlight a suitable procedure for assessing the spatial and temporal occurrence of complex landslides over large areas. [ABSTRACT FROM AUTHOR]

The paper focuses on the rapid drawdown of earth dams in the hypothesis that a prompt reservoir lowering is needed soon after a strong earthquake. The interest on such a topic comes from the fact that in Italy and worldwide there are many large dams placed very close to active faults. In this case, the dam may be asked to face the earthquake first and the rapid drawdown later to face an emergency state. The problem has been numerically investigated with reference to a zoned earth dam (Campolattaro Dam) placed in a highly seismic area of Southern Italy. To solve the overall boundary value problem, encompassing several stages of the dam lifetime, a 2D finite difference model has been solved through the FLAC2D code, implementing a coupled transient seepage formulation, which accounts for partial saturation of the soil during the drawdown stage. Unlike past literature studies, in which the drawdown stage was modelled without accounting for the past loading history of the dam, in the performed simulation the drawdown stage was placed at the end of a quite real sequence of events, encompassing the embankment construction, the reservoir impounding, and earthquake scenarios compatible with the dam site seismic hazard. The performed analyses pointed out that a seismic stage previously experienced by the dam could further contribute to decreasing dam stability during the drawdown especially during the first stages of reservoir lowering. In addition, the faster the drawdown, the smaller the dam safety factor against stability (FOS) with more prominent effects of the initial (pre-drawdown) soil conditions. [ABSTRACT FROM AUTHOR]

Our results provide a first step to make the formal analysis rigorous in terms of 1 c 2 proposed by Chandrasekhar [S. Chandrasekhar, The post-Newtonian equations of hydrodynamics in general relativity, Astrophys. J.142 (1965) 1488–1512; S. Chandrasekhar, post-Newtonian equations of hydrodynamics and the stability of gaseous masses in general relativity, Phys. Rev. Lett.14 (1965) 241–244], motivated by the methods of Einstein, Infeld and Hoffmann, see Thorne [K. S. Thorne, The general-relativistic theory of stellar structure and dynamics, in Proc. Int. School of Physics "Enrico Fermi," Course XXXV, at Varenna, Italy, July 12–24, 1965, ed. L. Gratton (Academic Press, 1966), pp. 166–280]. We consider the non-relativistic limit for the local smooth solutions to the free boundary value problem of the cylindrically symmetric relativistic Euler equations when the mass energy density includes the vacuum states at the free boundary. For large enough (rescaled) speed of light c and suitably small time T , we obtain uniform, with respect to c , "a priori" estimates for the local smooth solutions. Moreover, the smooth solutions of the cylindrically symmetric relativistic Euler equations converge to the solutions of the classical compressible Euler equation at the rate of order 1 c 2 . [ABSTRACT FROM AUTHOR]

ABSTRACT The sediment flux from a catchment is driven by tectonics and climate but is moderated by the geomorphic response of the landscape system to changes in these two boundary conditions. Consequently, catchment response time and the non-linear behavior of landscapes in response to boundary condition change control the downstream propagation of climatic or tectonic perturbations from catchments to neighboring basins. In order to investigate the impact of catchment response time on sediment flux, we integrated a spatially-lumped numerical model PaCMod, with new routines simulating the evolution of landscape morphology and erosion rates under tectonic and climatic forcing. We subsequently applied the model to reconstruct the sediment flux from a tectonically perturbed catchment in central Italy. Finally, we coupled our model to DeltaSim, a process-response model simulating fluvio-deltaic stratigraphy, and investigated the impact of catchment response time on stratigraphy, using both synthetic scenarios and a real world system (Fucino Basin, central Italy). Our results demonstrate that the differential response of geomorphic elements to tectonic and climatic changes induces a complex sediment flux signal, and produces characteristic stratigraphic architectures and shoreline trajectories. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]