Dipartimento di Ingegneria Civile - Tesi di Dottorato

Permanent URI for this collectionhttps://lisa.unical.it/handle/10955/99

Questa collezione raccoglie le Tesi di Dottorato Dipartimento di Ingegneria Civile dell'Università della Calabria.

Browse

Subject: search.filters.subject.Modellazione numerica

Search Results

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    New on-line model for shoreline evolution at beaches composed of not cohesive grains of any size
    (Università della Calabria, 2020-02-12) Francone, Antonio; Furgiuele, Franco; Tomasicchio, Giuseppe Roberto; Frega, Ferdinando
    Over recent decades, efforts have been made to find robust methods for predicting shoreline evolution near to the coastal structures. This requires a rigorous understanding of the key coastal processes that drive sediment transport, and how they are impacted by the presence of structures. Once this understanding is reached, a method for predicting morphological shoreline evolution is required. In this context, numerical modelling plays an important role. A new one-line model for shoreline evolution at beaches composed of not cohesive grains of any size is proposed: the General Shoreline beach (GSb). GSb model is based on the one-line theory, for which it is assumed that the equilibrium beach profile remains unchanged (Dean, 1990), thereby allowing beach change to be described uniquely in terms of the shoreline position. The longshore sediment transport rate is estimated by means of a general formula/procedure (Tomasicchio et al., 1994; Lamberti and Tomasicchio, 1997; Tomasicchio et al., 2013; Tomasicchio et al., 2015) combining an energy flux approach with an empirical/statistical relationship between the waveinduced forcing and the number of moving units. The uniqueness of the proposed new one-line model consists in the possibility to simulate beach change, including the effects of coastal structures (i.e. groynes, detached breakwaters), at a mound composed of not cohesive grains of any size, from sand to rock units. Despite other existing models, the GSb model presents a calibration factor, KGSb solely and it has been calibrated and verified against field and laboratory data on sandy and mixed beach (sand and gravel) referring to simple groyne and detached breakwater (Ming and Chiew, 2000; Hamilton et al., 2001; Martin-Grandes et al., 2009; Medellin et al., 2018;). Optimal values of KGSb, valid for different types of not cohesive grains and coastal structures, have been reported. It is showed that the GSb model can be considered a reliable engineering tool to conduct morphodynamics studies. A demo version of the GSb model, for Mac and Windows systems, has been released for the scientific community and is available at www.scacr.eu.
  • Thumbnail Image
    Item
    A Comprehensive analysis of hydrological benefits of low impact development techniques: experimental investigation and numerical modeling
    (Università della Calabria, 2020-03-05) Palermo, Stefania Anna; Furgiuele, Franco; Piro, Patrizia
    Urban floods, recently increasing due to the combine effect of climate change and urbanization, represent a potential risk to human life, economic assets and environment. In this context, the traditional urban drainage techniques seem to be inadequate for the purpose, therefore a transition towards an innovative sustainable and resilient urban stormwater management is a valid solution. One promising strategy is the implementation of decentralized stormwater controls, also known as Low Impact Development (LID) systems that provide several benefits at multiple scales. Despite several studies demonstrated the LIDs’ capability in terms of surface runoff reduction, the transition towards a sustainable urban drainage system, which includes these techniques, seems to be very slow. One of the key scientific limiting factors can be found in the lack of comprehensive analyses able to highlight the hydrological performance and the physical processes involved in LID systems at multiple spatial scale and by considering long-term experimental data. The complexity of the physical processes, involved in each specific LIDs stratigraphy, requires modeling tools able to accurately interpret their hydraulic behaviour, as well as to correlate their hydrologic efficiency with the management of stormwater in the surrounding urban area. For these reasons, so far different empirical, conceptual and mechanistic models have been proposed, however in many of these studies, the hydrological parameters, as well as the physical ones were not properly investigated, limiting the analysis only to specific factors, or by considering literature values for the numerical modeling. Thus, principal aim of this thesis is to present a comprehensive analysis of the hydrological benefits of LID techniques by experimental investigation and numerical modeling. To achieve this goal, several analyses were carried out by considering different: LID systems, spatial scales, weather conditions, modeling investigation, as well as mathematical optimization approaches. Monitored data at the full scale implementation and laboratory measurements were used to support the numerical modeling. More in detail, first a global sensitivity analysis (GSA), based on the Elementary Effect Test (EET) was applied to a PCSWMM hydrodynamic model of the University Campus Innsbruck, which combines traditional drainage infrastructures and low impact development techniques, as Rain Gardens. In this regard, main findings have showed that soil hydraulic parameters considered in the model, (i.e., principally Soil Hydraulic Conductivity and Seepage Rate) were the most sensitive parameters. Therefore, the identification of these properties for LID systems is crucial in order to correctly evaluate their hydraulic performance. Starting from this finding the analysis of the hydrological efficiency of a full-scale extensive green roof, located at University of Calabria in Mediterranean Climate was assessed, by considering field monitored hydrological data, as well as soil hydraulic properties evaluated in lab, and a modeling analysis. Thus, first a field monitoring campaign for one year was carried out, and then hydrological performance indices on an event scale were evaluated. The findings have revealed the optimal behaviour of the specific green roof in Mediterranean climate, which presents an average value of Subsurface Runoff Coefficient of 50.4% for the rainfall events with a precipitation depth more than 8 mm. Later, to evaluate the influence of increasing values of substrate depths (6 cm, 9 cm, 12 cm, 15 cm) on green roof retention capacity, the hydraulic properties of the soil materials were first investigated in Laboratory, by the simplified evaporation method, and then considered for the implementation of the mechanistic model HYDRUS 1D. The results obtained in this phase have showed how the considered substrate depths were able to achieve a runoff volume reduction of 22% to 24%. Thus, as the outflow volume reduction achieved by increasing the soil depth was not significant, the ideal depth for specific soil substrate would be 6 centimetres. Following this study, and based on the findings obtained at building scale, next phase was focused on the analysis of hydrological effectiveness of Low Impact development solutions at largeurban scale in a south Italian case study. This investigation was carried out by considering different LID conversion scenarios by a predictive conceptual model (PCSWMM). In this regards, a specific permeable pavement and green roof, developed and installed at University of Calabria, were considered for the model implementation. Globally, modeling results have confirmed the suitability of these LID solutions to reduce surface runoff even if just a small percentage (30%) of the impervious surfaces is converted. By considering all of the findings, previous achieved by experimental and modelig investigation, it emerged that many aspects related to LIDs design and operation, as well as the choice of the facility and its location can affect the results in terms of hydraulic efficiency. In this regard, a mathematical optimization approach to consider several aspects together could be a suitable tool for designers of LID systems and experts in the field. Therefore, in the last part of the work, new Mathematical Optimization Approaches for LID techniques were evaluated. More in detail, the optimization of rainwater harvesting systems, by using TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) and Rough Set method as Multi-Objective Optimization approaches, was carried out. The results have demonstrated that these approaches could provide an additional tool to identify the ideal system. In conclusion, main findings of this thesis confirm the suitability of LID systems for urban stormwater management providing useful suggestions for their design and tools for assessing their hydrological effectiveness, analysing physical and hydrological parameters that affect their operation, introducing advanced concepts for the optimization of LID systems, therefore providing a significant and innovative contribution for the improvement of scientific research in the field and the spread of these sustainable techniques.
  • Thumbnail Image
    Item
    Probabilistic assessment of the seismic performance of two earth dams in Southern Italy using simplified and advanced constitutive models
    (Università della Calabria, 2021-06-16) Regina, Gianluca; Conte, Enrico; Cairo, Roberto; Zimmaro, Paolo; Ziotopoulou, Katerina
    The large majority of existing earth dams were designed with old standards, which often accounted for the effects of earthquakes in a simplified manner. Nowadays, safety assessment of these structures is becoming of great importance, particularly for dams suffering the effects of ageing. This study presents a fully probabilistic approach to evaluate the seismic performance of two critical earth dams in the Calabria region, a seismically active area in Southern Italy. One of them (the Farneto del Principe dam) is not susceptible to liquefaction, whereas the other dam (the Angitola dam) is founded on potentially liquefiable soils. Seismic input motions are derived from site-specific probabilistic approaches. Non-ergodic ground response is implemented within a probabilistic seismic hazard analysis (PSHA) framework for one of the two dam sites. This non-ergodic PSHA is derived from numerical amplification functions based on one-dimensional simulations. Such well-documented early application of non-ergodic PSHA for earth dams in Italy may encourage a transformational shift from years of past practices based on deterministic amplification functions merged with PSHA results by means of hybrid approaches. Simplified (i.e., using the Mohr–Coulomb failure criterion coupled with a simplified hysteretic procedure) and advanced (i.e., PM4Sand and PM4Silt) constitutive models are used to perform a comprehensive numerical simulation program for both dams. Field and laboratory geotechnical characterization data are used to calibrate these models. This calibration process is fully documented and potential issues discussed. Such fully-documented calibration process will enable future studies on similar infrastructure systems when advanced constitutive models are necessary. Shear strain and deformation patterns are analyzed and discussed, showing that for the Farneto del Principe dam (comprising non-liquefiable materials) both constitutive models provide similar results. However, when potentially liquefiable soils are involved, advanced constitutive models are necessary to capture the complexity and nuances of such materials. This effect is evident for the Angitola dam. For both dams, seismic vulnerability is analyzed by means of analytical fragility functions for various damage mechanisms and intensity measures. Such fragility functions are based on nonlinear deformation analyses within the multiple stripe analysis framework. All fragility functions derived in this study are shown and main outcomes are illustrated by summary tables reporting mean and standard deviation values of these curves. Finally, the efficiency and predictability of various ground motion intensity measures to predict different damage levels and mechanisms are calculated for both dams. Predictability of recent semi-empirical ground motion models is also calculated for all analyzed intensity measures. Overall, results from this analysis indicate that velocity-based ground motion properties, such as Peak Ground Velocity, Arias Intensity, Cumulative Absolute Velocity, and Cumulative Absolute Velocity after application of a 0.05 𝑚𝑠2 threshold acceleration provide good efficiencies in predicting damage. These intensity measures are the best in predicting damage states for both dams and all damage mechanisms. However, some of them are more predictable than others. After merging efficiency and predictability information, the best intensity measure to predict damage is the Cumulative Absolute Velocity, followed by the Arias intensity.