Dipartimento di Ingegneria Civile - Tesi di Dottorato
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Questa collezione raccoglie le Tesi di Dottorato Dipartimento di Ingegneria Civile dell'Università della Calabria.
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Item Dynamic Methods for Monitoring Structural Health: analytical and experimental aspects(Università della Calabria, 2018-11) Miceli, Angela; Zinno, Raffaele; Carbone, VincenzoItem Analisi del comportamento non-lineare dei materiali compositi con microstruttura periodica(2009) Sgambittera, Girolamo; Olivito, Renato Sante; Bruno, Domenico; Greco, FabrizioIn the present thesis the macroscopic non-linear behavior of composite materials with a periodic and heterogeneous microstructure is studied. There are many different kinds of phenomena that produce non-linear effects in composite materials, for example intralaminar damage, delamination and microbucking in fiber reinforced composite or micro-cracking in cellular materials. In this work attention is devoted to the mechanical modeling of nonlinear phenomena associated to the presence of micro-cracks in the context of linear elasticity and of microscopic instabilities in the framework of the finite strain theory. Applications have been developed with reference to microstructures of cellular type and with embedded inclusions. The thesis is structured according to the following chapters: -In the first chapter the fundamental concepts of the finite strains theory are recalled. The constitutive relations associated to a class of conjugate stress-strain pairs are introduced. The basic expressions of the incremental constitutive laws are shown with special reference to incrementally linear constitutive laws. Finally the stability and the uniqueness of the equilibrium solution are analyzed. -In the second chapter, after an introduction about the homogenization techniques, the micro and macro stability phenomena occurring in composite materials with a periodic microstructure are studied from a theoretical point of view in the context of the finite strains theory. The formulation starts from a variational formulation of the problem. Novel macroscopic measures of micro-structural stability are introduced corresponding to the positive definiteness of the homogenized moduli tensors relative to a class of conjugate stress-strain pairs and their effectiveness to obtain a conservative prediction of the microscopic primary instability load is pointed out. Analysis of these stability phenomena plays a fundamental role because often the collapse of composite materials with periodic microstructure is related to microstructural instabilities. In addition the microscopic stability analysis establishes the region of validity of the standard homogenization procedure based on the unit cell procedure. -In the third chapter, in the context of the small strains theory, non-linear phenomena are presented with reference to composite materials with a porous microstructure containing micro-cracks spreading from the voids. The fundamental techniques of homogenization are applied in conjunction with fracture mechanics theory and interface models. The energy release rate is evaluated through the J-integral technique. -In the fourth chapter some numerical applications carried out by means of a one-way coupled finite element code, are proposed. In the first section the numerical results will be introduced with reference to the theoretical aspects developed in the second chapter. Numerical analyses are addressed to composite materials with a periodic microstructure, namely a porous microstructure and a particle-reinforced microstructure. The adopted constitutive law is hyperelastic. Periodic boundary conditions will be used for the microstructure, and uniaxial and equibiaxial loading conditions are considered. Numerical analyses are able to show the exact region of microscopic stability, obtained by taking into account all the microstructural details, and the region of macroscopic stability, determinate by studying homogenized material properties. To elaborate macroscopic criteria able to give a conservative prediction of the microstructural stability, different measures of macroscopic instability are introduced with reference to work conjugate strain-stress measures. In the second section of this chapter a numerical analyses with reference to the micromechanical model proposed in the third chapter is developed. In this case the microstructure adopted for the composite materials is a cellular microstructure in which there is the presence of two micro-cracks advancing symmetrically from the void. The microstructure is subjected to three different boundary conditions namely respectively: linear displacements, periodic fluctuations and antiperiodic tractions and uniform tractions. The objective of this section is to verify the validity of the homogenization technique in the prediction of micro-crack evolution phenomena, for composites with locally periodic microstructure. The energy release rate obtained through the micromechanical model will be compared with a 2D composite structure composed by a regular arrangement of 5x5 unit cells. The composite structure is subjected to two different boundary conditions: the former is associated with the absence of contact between the surfaces of the micro-cracks, on the contrary in the latter case there is the presence of the contact. This type of comparison allows to investigate the accuracy of the proposed procedure in presence of macroscopic tension and strain gradients.Item 40° N sole e contesto nella progettazione di spazi urbani mediterranei(2009) Carbone, Ivana; Rossi, Franco; Cannavò, PaolaItem <> quartiere sostenibile. Indirizzi guida per un progetto di qualità(2012-12-17) Celani, Pierfrancesco; Bilotta, Eleonora; Cannavò, PaolaItem Lo sviluppo dei sistemi di trasporto collettivo: studio di un indice per la determinazione del comfort a bordo.(2017-06-16) Tassitani, Antonio; Furgiuele, Franco; Astarita, VittorioItem Adeguamento antisismico di edifici in c.a. irregolari in pianta mediante l'utilizzo di controventi dissipativi: modellazione, progettazione ed analisi non lineare(2017-06-16) Pedace, Emilia; Furgiuele, Franco; Mazza, FabioItem Soluzioni innovative per lo sviluppo della mobilità sostenibile: aspetti metodologici e sperimentali(2017-06-16) Rogano, Daniele; Furgiuele, Franco; Guido, GiuseppeItem Turbulence characteristics in open-‐channel flows with highly rough beds.(2017-10-27) Ferraro, Domenico; Furgiuele, Franco; Gaudio, RobertoRiver motion is one of the most attractive and fascinating phenomena in nature. Since ancient times many scientists have been drawn into a vortex of confusion observing river motion. Flow observation is often simplified, running tests in a laboratory under controlled conditions, in order to test a specific phenomenon of a much more complex issue. A great number of these phenomena has been collected by researchers throughout the history of science, and other researchers have tried to merge the available knowledge to clarify the tangled phenomena. This work is focused on the turbulent characteristics of Open-Channel Flows (OCFs) over a highly rough bed. The use of coarse sediments is an attractive technique to solve many problems in rivers as well as to safeguard aquatic life. Issues like sediment transport phenomena or erosion and local scour, e.g. at bridge piers and abutments, can be counteracted by introducing coarse sediments. In this work the bed roughness effect on the turbulence characteristics of the flow is investigated through the relative submergence parameter Δ, which is the ratio between the roughness characteristic dimension and the water depth. Most of the theories and literature works has been developed for smooth-wall flows and rough-bed flows at very high relative submergence, whereas its applicability in OCFs with low relative submergence remains questionable; the simplest example is the velocity distribution (i.e., the universal logarithmic law). This thesis aims at improving the knowledge of turbulence structure developed over a highly rough bed in OCFs by varying the relative submergence. According to the relative submergence definition given before, it can be changed by modifying the water depth for a fixed roughness or varying the roughness keeping the water depth constant. The choice settled on the second strategy, because of the measurement instrument configuration. It will be described in detail in the chapter “Experimental equipment and procedures”. The relative submergence varied in the range from 3.13 to 10.07. Three long-duration experiments (each one with a given coarse sediment size) were performed in uniform flow conditions by using a 100 Hz ADV down-looking probe, in order to record the 3D velocity vector in each point of a given grid of measurements. The contribution of the Reynolds stress, the viscous and the form-induced shear stress was analysed, as well as the averaged velocity profiles, second- and third-order moments . A statistical tool will be proposed to verify the frozen-in Taylor hypothesis by comparing two typical time-scales, namely the large scale advection time and the characteristic nonlinear time. The proposed method based on the characteristic eddies timescales is more restrictive with respect to the classic frozen-in Taylor hypothesis, in which a simple comparison of the flow velocity and the fluctuation magnitude is made. Furthermore, one-point temporal correlations analysis will be performed in order to give a first indication of the integral scales lengths along the channel varying the relative submergence. Spectral analysis is introduced both in the frequency and in wavenumber domain. In experimental practice it is quite hard to obtain direct measures, which can allow computing directly a wavenumber spectrum. Temporal velocity signals are commonly recorded in a single point, and they are used to compute the frequency spectrum and then converted to wavenumber spectrum through the Taylor frozen-in hypothesis. Hence, the k−5/3 slope is investigated in the longitudinal velocity spectra. k is the wavenumber. Spectral analysis will be introduced in order to test the observed k−5/3 slope, in order to confirm that the inertial subrange is well visible at the investigated Re numbers. Furthermore, the validity of the −5/3 scaling region will be also tested by using the third-order longitudinal velocity structure function, which is expressed as a function of the turbulent kinetic energy (TKE) dissipation rate. The third-order longitudinal velocity structure function will be also used to provide an estimate of the magnitude of the TKE dissipation rate. In addition, in order to quantify the energy contribution of different eddyscales, premultiplied spectra will be employed. Thanks to this analysis, the Large Scales (LSs) and the Very Large Scale (VLSs) will be investigated. These scales will be associated with a characteristic wavenumber and intensity. ADV velocity measurement also allows exploring the longitudinal-vertical velocity co-spectra. In order to locate the normalized wavenumber associated with the peak in the premultiplied spectra, a systematic procedure to find the correct position of the peaks based on the center of mass concept will be proposed. Moreover, the peak distribution over the water depth will be plotted in inner and outer coordinates.Item <> modello di gestione delle reti idriche in condizioni di emergenza(2017-06-16) Caruso, Olga; Furgiuele, Franco; Fiorini Morosini, AttilioItem On the use of mechanistic modeling for the numerical analysis of low impact developments techniques(2017-06-16) Brunetti, Giuseppe; Furgiuele, Franco; Piro, PatriziaThe increasing frequency of flooding events in urban catchments related to an increase in impervious surfaces highlights the inadequacy of traditional urban drainage systems. Low-impact developments (LIDs) techniques have proven to be valuable alternatives for stormwater management and hydrological restoration, by reducing stormwater runoff and increasing the infiltration and evapotranspiration capacity of urban areas. However, the lack of diffusion of adequate modelling tools represents a barrier in designing and constructing such systems. Mechanistic models are reliable and accurate tools for analysis of the hydrologic behaviour of LIDs, yet only a few studies provide a comprehensive numerical analysis of the hydrological processes involved and test their model predictions against field-scale data. Moreover, their widespread use among urban hydrologists suffers from some limitations, namely: complexity, model calibration and computational cost. This suggest that more research is needed to address these issues and examine the applicability of this kind of models. Thus, the main aim of this thesis was to investigate the benefits and the limitations in the use of mechanistic modelling for LIDs analysis. In this view, the mechanistic modelling approach has been used to simulate the hydraulic/hydrologic behaviour of three different LIDs installed at the University of Calabria: an extensive green roof, a permeable pavement and a stormwater filter. Each case study was used to examine a particular modelling aspect. The morphological and hydrological complexity of the green roof required the use of a three-dimensional mechanistic model, which was validated against experimental data with satisfactory results. The measured soil hydraulic properties of the soil substrate highlighted important characteristics, accounted in the simulation. The validated model was used to carry out a hydrological analysis of the green roof and its hydrological performance during the entire simulated period as well as during single precipitation events. Conversely, a one-dimensional mechanistic model was used to simulate the hydraulic behaviour of a permeable pavement, whose parameters were calibrated against experimental data. A Global Sensitivity Analysis (GSA) followed by a Monte Carlo filtering highlighted the influence of the wear layer on the hydraulic behaviour of the pavement and identified the ranges of parameters generating behavioural solutions in the optimization framework. Reduced ranges were then used in the calibration procedure conducted with the metaheuristic Particle swarm optimization (PSO) algorithm for the estimation of hydraulic parameters. The calibrated model was then validated against an independent set of data with good results. Finally, to address the issue of computational cost, the surrogate-based modelling technique has been applied to calibrate a two-dimensional mechanistic model used to simulate the hydraulic behaviour of a stormwater filter. The kriging technique was utilized to approximate the deterministic response of the mechanistic model. The validated kriging model was first used to carry out a Global Sensitivity Analysis of the unknown soil hydraulic parameters of the filter layer. Next, the Particle Swarm Optimization algorithm was used to estimate their values. Finally, the calibrated model was validated against an independent set of measured outflows with optimal results. Results of the present thesis confirmed the reliability of mechanistic models for LIDs analysis, and gave a new contribution towards a much broader diffusion of such modelling tools.