Contribution to assessing the stiffness reduction of structural elements in the global stability analysis of precast concrete multi-storey buildings

This study deals with the reduction of the stiffness in precast concrete structural elements of multi-storey buildings to analyze global stability. Having reviewed the technical literature, this paper present indications of stiffness reduction in different codes, standards, and recommendations and compare these to the values found in the present study. The structural model analyzed in this study was constructed with finite elements using ANSYS® software. Physical Non-Linearity (PNL) was considered in relation to the diagrams M x N x 1/r, and Geometric Non-Linearity (GNL) was calculated following the Newton-Raphson method. Using a typical precast concrete structure with multiple floors and a semi-rigid beam-to-column connection, expressions for a stiffness reduction coefficient are presented. The main conclusions of the study are as follows: the reduction coefficients obtained from the diagram M x N x 1/r differ from standards that use a simplified consideration of PNL; the stiffness reduction coefficient for columns in the arrangements analyzed were approximately 0.5 to 0.6; and the variation of values found for stiffness reduction coefficient in concrete beams, which were subjected to the effects of creep with linear coefficients from 0 to 3, ranged from 0.45 to 0.2 for positive bending moments and 0.3 to 0.2 for negative bending moments.

Influence of chest wall on lung mechanics during inspiration

RATIONALE: The interaction between lungs and chest wall influences lung volume, that determines lung history during respiration cycle. In this study, the influence of chest wall mechanics on respiratory system is assessed by the evaluation of inspiration pressure-volume curve (PV curve) under three different situations: closed-chest, open-chest and isolated lung. The PV curve parameters in each situation allow us to further understand the role played by different chest wall elements in the respiratory function. Methods: Twenty-four male Wistar rats (236 ± 29 g) were used. The animals were weighted and then anesthetized with xylazine 2% (O,SmL/kg) and ketamine 10% (0,9mL/kg), exsanguinated and later tracheostomies with a metallic cannula (14 gauge).The cannula was connected to an automatic small animal insufflator. This setup was connected to a pressure transducer (32 samples/s). The 24 animals were randomly separated in three groups:(i) closed chest,(ii) open chest and (iii) isolated lung. The rats were insufflated with 20mL quasi-statically (constant speed of 0,1mUs). lnsufflated volume and measured pressure data were kept and PV curves were obtained for all animals. The PV curves were fitted (non-linear least squares) against the sigmoid equation (1) to obtain the sigmoid equation parameters (a,b,c,d). Elastance measurements were obtained from linear regression of pressure/volume measurements in a 0,8s interval before and after the calculated point. Results: The parameters a,b and c showed no significant change, but the parameter d showed a significant variation among the three groups. The initial elastance also varied between open and closed chest, indicating the need of a higher pressure for the lung expansion, as can be seen in Table 1. Conclusion: A supporting effect of the chest wall was observed at the initial moments of inspiration, observed as a higher initial elastance in open chest situations than in closed chest situations (p=0,00001). The similar initial elastance for the isolated lung and closed chest may be explained by the specific method used for the isolated lung experiment. As the isolated lung is supported by the trachea vertically, the weight of the tissue may have a similar effect of the residual negative pressure in the thorax, responsible for maintaining the residual volume.

Influence of chest wall on lung mechanics during inspiration.

RATIONALE: The interaction between lungs and chest wall influences lung volume, that determines lung history during respiration cycle. In this study, the influence of chest wall mechanics on respiratory system is assessed by the evaluation of inspiration pressure-volume curve (PV curve) under three different situations: closed-chest, open-chest and isolated lung. The PV curve parameters in each situation allow us to further understand the role played by different chest wall elements in the respiratory function. Methods: Twenty-four male Wistar rats (236 ± 29 g) were used. The animals were weighted and then anesthetized with xylazine 2% (0,5mL/kg) and ketamine 10% (0,9mL/kg), exsanguinated and later tracheostomized with a metallic cannula (14 gauge). The cannula was connected to an automatic small animal insufflator. This setup was connected to a pressure transducer (32 samples/s). The 24 animals were randomly separated in three groups: (i) closed chest, (ii) open chest and (iii) isolated lung. The rats were insufflated with 20mL quasi-statically (constant speed of 0,1mL/s). Insufflated volume and measured pressure data were kept and PV curves were obtained for all animals. The PV curves were fitted (non-linear least squares) against the sigmoid equation (1) to obtain the sigmoid equation parameters (a,b,c,d). Elastance measurements were obtained from linear regression of pressure/volume measurements in a 0,8s interval before and after the calculated point. Results: The parameters a, b and c showed no significant change, but the parameter d showed a significant variation among the three groups. The initial elastance also varied between open and closed chest, indicating the need of a higher pressure for the lung expansion, as can be seen in Table 1. Table 1: Mean and Standard Deviation of parameters obtained for each protocol. Protocol: Closed Chest – a (mL) -0.35±0.33; b (mL) 13.93±0.89; c (cm H2O) 21.28±2.37; d (cm H2O) 6.17±0.84; r²** (%) 99.4±0.14; Initial Elastance* (cm H2)/mL) 12.72±6.66; Weight (g) 232.33±5.72. Open Chest - a (mL) 0.01±0.28; b (mL) 14.79±0.54; c (cm H2O) 19.47±1.41; d (cm H2O) 3.50±0.28; r²** (%) 98.8±0.34; Initial Elastance* (cm H2)/mL) 28.68±2.36; Weight (g) 217.33±7.97. Isolated Lung - a (mL) -0.09±0.46; b (mL) 14.22±0.75; c (cm H2O) 21.76±1.43; d (cm H2O) 4.24±0.50; r²** (%) 98.9±0.19; Initial Elastance* (cm H2)/mL) 7.13±8.85; Weight (g) 224.33±16.66. * Elastance measures in the 0-0,1 mL range. ** Goodness of sigmoid fit versus measured data Conclusion: A supporting effect of the chest wall was observed at the initial moments of inspiration, observed as a higher initial elastance in open chest situations than in closed chest situations (p=0,00001). The similar initial elastance for the isolated lung and closed chest may be explained by the specific method used for the isolated lung experiment. As the isolated lung is supported by the trachea vertically, the weight of the tissue may have a similar effect of the residual negative pressure in the thorax, responsible for maintaining the residual volume.

Creep and damage models for the service behaviour of structural members

Deformability is often a crucial to the conception of many civil-engineering structural elements. Also, design is all the more burdensome if both long- and short-term deformability has to be considered. In this thesis, long- and short-term deformability has been studied from the material and the structural modelling point of view. Moreover, two materials have been handled: pultruded composites and concrete. A new finite element model for thin-walled beams has been introduced. As a main assumption, cross-sections rigid are considered rigid in their plane; this hypothesis replaces that of the classical beam theory of plane cross-sections in the deformed state. That also allows reducing the total number of degrees of freedom, and therefore making analysis faster compared with twodimensional finite elements. Longitudinal direction warping is left free, allowing describing phenomena such as the shear lag. The new finite-element model has been first applied to concrete thin-walled beams (such as roof high span girders or bridge girders) subject to instantaneous service loadings. Concrete in his cracked state has been considered through a smeared crack model for beams under bending. At a second stage, the FE-model has been extended to the viscoelastic field and applied to pultruded composite beams under sustained loadings. The generalized Maxwell model has been adopted. As far as materials are concerned, long-term creep tests have been carried out on pultruded specimens. Both tension and shear tests have been executed. Some specimen has been strengthened with carbon fibre plies to reduce short- and long- term deformability. Tests have been done in a climate room and specimens kept 2 years under constant load in time. As for concrete, a model for tertiary creep has been proposed. The basic idea is to couple the UMLV linear creep model with a damage model in order to describe nonlinearity. An effective strain tensor, weighting the total and the elasto-damaged strain tensors, controls damage evolution through the damage loading function. Creep strains are related to the effective stresses (defined by damage models) and so associated to the intact material.

Kinematic description of the rupture from strong motion data: strategies for a robust inversion

We present a non linear technique to invert strong motion records with the aim of obtaining the final slip and rupture velocity distributions on the fault plane. In this thesis, the ground motion simulation is obtained evaluating the representation integral in the frequency. The Green’s tractions are computed using the discrete wave-number integration technique that provides the full wave-field in a 1D layered propagation medium. The representation integral is computed through a finite elements technique, based on a Delaunay’s triangulation on the fault plane. The rupture velocity is defined on a coarser regular grid and rupture times are computed by integration of the eikonal equation. For the inversion, the slip distribution is parameterized by 2D overlapping Gaussian functions, which can easily relate the spectrum of the possible solutions with the minimum resolvable wavelength, related to source-station distribution and data processing. The inverse problem is solved by a two-step procedure aimed at separating the computation of the rupture velocity from the evaluation of the slip distribution, the latter being a linear problem, when the rupture velocity is fixed. The non-linear step is solved by optimization of an L2 misfit function between synthetic and real seismograms, and solution is searched by the use of the Neighbourhood Algorithm. The conjugate gradient method is used to solve the linear step instead. The developed methodology has been applied to the M7.2, Iwate Nairiku Miyagi, Japan, earthquake. The estimated magnitude seismic moment is 2.6326 dyne∙cm that corresponds to a moment magnitude MW 6.9 while the mean the rupture velocity is 2.0 km/s. A large slip patch extends from the hypocenter to the southern shallow part of the fault plane. A second relatively large slip patch is found in the northern shallow part. Finally, we gave a quantitative estimation of errors associates with the parameters.

Expressions- und Funktionsanalysen von Neuroglobin und Cytoglobin

Im Rahmen der vorliegenden Dissertation wurden Untersuchungen zur Expression und Funktion der respiratorischen Proteine Neuroglobin (Ngb) und Cytoglobin (Cygb) in Vertebraten durchgeführt. Beide Globine wurden erst kürzlich entdeckt, und ihre Funktionen konnten trotz vorliegender Daten zur Struktur und biochemischen Eigenschaften dieser Proteine bisher nicht eindeutig geklärt werden. Im ersten Abschnitt der vorliegenden Arbeit wurde die zelluläre und subzelluläre Lokalisation von Neuroglobin und Cytoglobin in murinen Gewebeschnitten untersucht. Die Expression von Ngb in neuronalen und endokrinen Geweben hängt offensichtlich mit den hohen metabolischen Aktivitäten dieser Organe zusammen. Insbesondere im Gehirn konnten regionale Unterschiede in der Ngb-Expression beobachtet werden. Dabei korrelierte eine besonders starke Neuroglobin-Expression mit Gehirnbereichen, die bekanntermaßen die höchsten Grundaktivitäten aufweisen. In Anbetracht dessen liegt die Funktion des Neuroglobins möglicherweise im basalen O2-Metabolismus dieser Gewebe, wobei Ngb als O2-Lieferant und kurzfristiger O2-Speicher den vergleichsweise hohen Sauerstoffbedarf vor Ort sicherstellen könnte. Weitere Funktionen in der Entgiftung von ROS bzw. RNS oder die kürzlich publizierte mögliche Rolle des Ngb bei der Verhinderung der Mitochondrien-vermittelten Apoptose durch eine Reduktion des freigesetzten Cytochrom c wären darüber hinaus denkbar. Die Cygb-Expression im Gehirn beschränkte sich auf relativ wenige Neurone in verschiedenen Gehirnbereichen und zeigte dort vorwiegend eine Co-Lokalisation mit der neuronalen NO-Synthase. Dieser Befund legt eine Funktion des Cytoglobins im NO-Metabolismus nahe. Quantitative RT-PCR-Experimente zur mRNA-Expression von Ngb und Cygb in alternden Säugern am Bsp. der Hamsterspezies Phodopus sungorus zeigten keine signifikanten Änderungen der mRNA-Mengen beider Globine in alten im Vergleich zu jungen Tieren. Dies widerspricht publizierten Daten, in denen bei der Maus anhand von Western Blot-Analysen eine Abnahme der Neuroglobin-Menge im Alter gezeigt wurde. Möglicherweise handelt es sich hierbei um speziesspezifische Differenzen. Die im Rahmen dieser Arbeit durchgeführte vergleichende Sequenzanalyse der humanen und murinen NGB/Ngb-Genregion liefert zum einen Hinweise auf die mögliche Regulation der Ngb-Expression und zum anderen eine wichtige Grundlage für die funktionellen Analysen dieses Gens. Es konnte ein minimaler Promotorbereich definiert werden, der zusammen mit einigen konservierten regulatorischen Elementen als Basis für experimentelle Untersuchungen der Promotoraktivität in Abhängigkeit von äußeren Einflüssen dienen wird. Bioinformatische Analysen führten zur Identifizierung des sog. „neuron restrictive silencer element“ (NRSE) im Ngb-Promotor, welches vermutlich für die vorwiegend neuronale Expression des Proteins verantwortlich ist. Die kontrovers diskutierte O2-abhängige Regulation der Ngb-Expression konnte hingegen anhand der durchgeführten komparativen Sequenzanalysen nicht bestätigt werden. Es wurden keine zwischen Mensch und Maus konservierten Bindestellen für den Transkriptionsfaktor HIF-1 identifiziert, der die Expression zahlreicher hypoxieregulierter Gene, z.B. Epo und VEGF, vermittelt. Zusammen mit den in vivo-Daten spricht dies eher gegen eine Regulation der Ngb-Expression bei verminderter Verfügbarkeit von Sauerstoff. Die Komplexität der Funktionen von Ngb und Cygb im O2-Stoffwechsel der Vertebraten macht den Einsatz muriner Modellsysteme unerlässlich, die eine sukzessive Aufklärung der Funktionen beider Proteine erlauben. Die vorliegende Arbeit liefert auch dazu einen wichtigen Beitrag. Die hergestellten „gene-targeting“-Vektorkonstrukte liefern in Verbindung mit den etablierten Nachweisverfahren zur Genotypisierung von embryonalen Stammzellen die Grundlage zur erfolgreichen Generierung von Ngb-knock out sowie Ngb- und Cygb-überexprimierenden transgenen Tieren. Diese werden für die endgültige Entschlüsselung funktionell relevanter Fragestellungen von enormer Bedeutung sein.

Comparison between analytical and numerical methods for the assessment of masonry arch bridges: Case study of Clemente Bridge on Savio river

This research has focused on the study of the behavior and of the collapse of masonry arch bridges. The latest decades have seen an increasing interest in this structural type, that is still present and in use, despite the passage of time and the variation of the transport means. Several strategies have been developed during the time to simulate the response of this type of structures, although even today there is no generally accepted standard one for assessment of masonry arch bridges. The aim of this thesis is to compare the principal analytical and numerical methods existing in literature on case studies, trying to highlight values and weaknesses. The methods taken in exam are mainly three: i) the Thrust Line Analysis Method; ii) the Mechanism Method; iii) the Finite Element Methods. The Thrust Line Analysis Method and the Mechanism Method are analytical methods and derived from two of the fundamental theorems of the Plastic Analysis, while the Finite Element Method is a numerical method, that uses different strategies of discretization to analyze the structure. Every method is applied to the case study through computer-based representations, that allow a friendly-use application of the principles explained. A particular closed-form approach based on an elasto-plastic material model and developed by some Belgian researchers is also studied. To compare the three methods, two different case study have been analyzed: i) a generic masonry arch bridge with a single span; ii) a real masonry arch bridge, the Clemente Bridge, built on Savio River in Cesena. In the analyses performed, all the models are two-dimensional in order to have results comparable between the different methods taken in exam. The different methods have been compared with each other in terms of collapse load and of hinge positions.

Störungstheoretische Behandlung relativistischer Korrekturen zu Gleichgewichtsstrukturen im Rahmen der Coupled-Cluster-Theorie

Quantenchemische Untersuchungen von Atomen und Molekülen haben in den letzten Jahren durch die systematische Erweiterung der Methoden und Computerresourcen zunehmend für die Interpretation und Vorhersage experimenteller Ergebnisse an Bedeutung gewonnen. Relativistische Effekte in der Chemie werden zum Beispiel für die gelbe Farbe von Gold und den flüssigen Aggregatzustand von Quecksilber verantwortlich gemacht und müssen daher in quantenchemischen Rechnungen berücksichtigt werden. Relativistische Effekte sind bei leichten Elementen oft so klein, daß sie in vielen quantenchemischen Betrachtungen vernachlässigt werden. Dennoch sind es gerade diese Beiträge, die verbleibende Abweichungen von noch so genauen nichtrelativistischen Rechnungen von ebenso genauen experimentellen Ergebnissen ausmachen können. Relativistische Effekte können auf viele Arten in quantenchemischen Rechnungen berücksichtigt werden. Eine Möglichkeit ist die Störungstheorie. Ein derartiger Ansatz ist die Mass-velocity-Darwin-Näherung, ein anderer die Direkte Störungstheorie. Hier entspricht die relativistische Energiekorrektur erster Ordnung der ersten Ableitung der Energie nach einem relativistischen Störparameter. Für eine Bestimmung der Gleichgewichtsstruktur eines Moleküls müssen die Kräfte auf die Atomkerne bestimmt werden. Diese entsprechen einer ersten Ableitung der Gesamtenergie nach den Kernkoordinaten. Eine Einbeziehung der relativistischen Effekte auf diese Kräfte erfordert daher die gemischte zweite Ableitung der Energie nach dem relativistischen Störparameter und den Kernkoordinaten. Diese relativistischen Korrekturen wurden in dem quantenchemischen Programmpaket ACES2 implementiert. Ein Resultat dieser Arbeit ist, daß nun erstmalig eine Implementierung analytischer Gradienten für die Berechnung relativistischer Korrekturen zu Strukturparametern mit Hilfe der relativistischen Störungstheorie für den Coupled-Cluster-Ansatz bereit steht. Die Coupled-Cluster-Theorie eignet sich besonders gut für die hochgenaue Vorhersage von molekularen Eigenschaften, wie der Gleichgewichtsstruktur. Im Rahmen dieser Arbeit wurde die Basissatzabhängigkeit der relativistischen Beiträge zu Energien, Strukturparametern und harmonischen Schwingungsfrequenzen im Detail untersucht. Für die hier untersuchten Moleküle sind die relativistischen Effekte und Effekte aufgrund der Elektronenkorrelation nicht additiv, so verkürzt die Berücksichtigung relativistischer Effekte bei Hartree-Fock-Rechnungen die Bindung in den Hydrogenhalogeniden, während die Einbeziehung der Elektronenkorrelation durch CCSD(T)-Rechnungen zu einer verlängerten Bindung im Fluorwasserstoff und weniger stark ausgeprägten Korrekturen im Chlor- und Bromwasserstoff führt. Für die anderen hier untersuchten mehratomigen Moleküle findet sich kein einheitlicher Trend; dies unterstreicht die Notwendigkeit expliziter Rechnungen. Damit steht ein leistungsfähiges und vielseitiges Werkzeug für die Berechnung relativistischer Korrekturen auf verschiedenste molekulare Eigenschaften zur Verfügung, das mit modernen, systematisch verbesserbaren quantenchemischen Methoden verknüpft ist. Hiermit ist es möglich, hochgenaue Rechnungen zur Vorhersage und Interpretation von Experimenten durchzuführen.

Fluid-structure interaction by a coupled lattice Boltzmann-finite element approach

In this thesis, a strategy to model the behavior of fluids and their interaction with deformable bodies is proposed. The fluid domain is modeled by using the lattice Boltzmann method, thus analyzing the fluid dynamics by a mesoscopic point of view. It has been proved that the solution provided by this method is equivalent to solve the Navier-Stokes equations for an incompressible flow with a second-order accuracy. Slender elastic structures idealized through beam finite elements are used. Large displacements are accounted for by using the corotational formulation. Structural dynamics is computed by using the Time Discontinuous Galerkin method. Therefore, two different solution procedures are used, one for the fluid domain and the other for the structural part, respectively. These two solvers need to communicate and to transfer each other several information, i.e. stresses, velocities, displacements. In order to guarantee a continuous, effective, and mutual exchange of information, a coupling strategy, consisting of three different algorithms, has been developed and numerically tested. In particular, the effectiveness of the three algorithms is shown in terms of interface energy artificially produced by the approximate fulfilling of compatibility and equilibrium conditions at the fluid-structure interface. The proposed coupled approach is used in order to solve different fluid-structure interaction problems, i.e. cantilever beams immersed in a viscous fluid, the impact of the hull of the ship on the marine free-surface, blood flow in a deformable vessels, and even flapping wings simulating the take-off of a butterfly. The good results achieved in each application highlight the effectiveness of the proposed methodology and of the C++ developed software to successfully approach several two-dimensional fluid-structure interaction problems.

Morphology and charge transport in conjugated polymers

To assist rational compound design of organic semiconductors, two problems need to be addressed. First, the material morphology has to be known at an atomistic level. Second, with the morphology at hand, an appropriate charge transport model needs to be developed in order to link charge carrier mobility to structure.rnrnThe former can be addressed by generating atomistic morphologies using molecular dynamics simulations. However, the accessible range of time- and length-scales is limited. To overcome these limitations, systematic coarse-graining methods can be used. In the first part of the thesis, the Versatile Object-oriented Toolkit for Coarse-graining Applications is introduced, which provides a platform for the implementation of coarse-graining methods. Tools to perform Boltzmann inversion, iterative Boltzmann inversion, inverse Monte Carlo, and force-matching are available and have been tested on a set of model systems (water, methanol, propane and a single hexane chain). Advantages and problems of each specific method are discussed.rnrnIn partially disordered systems, the second issue is closely connected to constructing appropriate diabatic states between which charge transfer occurs. In the second part of the thesis, the description initially used for small conjugated molecules is extended to conjugated polymers. Here, charge transport is modeled by introducing conjugated segments on which charge carriers are localized. Inter-chain transport is then treated within a high temperature non-adiabatic Marcus theory while an adiabatic rate expression is used for intra-chain transport. The charge dynamics is simulated using the kinetic Monte Carlo method.rnrnThe entire framework is finally employed to establish a relation between the morphology and the charge mobility of the neutral and doped states of polypyrrole, a conjugated polymer. It is shown that for short oligomers, charge carrier mobility is insensitive to the orientational molecular ordering and is determined by the threshold transfer integral which connects percolating clusters of molecules that form interconnected networks. The value of this transfer integral can be related to the radial distribution function. Hence, charge mobility is mainly determined by the local molecular packing and is independent of the global morphology, at least in such a non-crystalline state of a polymer.

Behaviour and applications of elastic waves in structures and metamaterials

The present thesis focuses on elastic waves behaviour in ordinary structures as well as in acousto-elastic metamaterials via numerical and experimental applications. After a brief introduction on the behaviour of elastic guided waves in the framework of non-destructive evaluation (NDE) and structural health monitoring (SHM) and on the study of elastic waves propagation in acousto-elastic metamaterials, dispersion curves for thin-walled beams and arbitrary cross-section waveguides are extracted via Semi-Analytical Finite Element (SAFE) methods. Thus, a novel strategy tackling signal dispersion to locate defects in irregular waveguides is proposed and numerically validated. Finally, a time-reversal and laser-vibrometry based procedure for impact location is numerically and experimentally tested. In the second part, an introduction and a brief review of the basic definitions necessary to describe acousto-elastic metamaterials is provided. A numerical approach to extract dispersion properties in such structures is highlighted. Afterwards, solid-solid and solid-fluid phononic systems are discussed via numerical applications. In particular, band structures and transmission power spectra are predicted for 1P-2D, 2P-2D and 2P-3D phononic systems. In addition, attenuation bands in the ultrasonic as well as in the sonic frequency regimes are experimentally investigated. In the experimental validation, PZTs in a pitch-catch configuration and laser vibrometric measurements are performed on a PVC phononic plate in the ultrasonic frequency range and sound insulation index is computed for a 2P-3D phononic barrier in the sonic frequency range. In both cases the numerical-experimental results comparison confirms the existence of the numerical predicted band-gaps. Finally, the feasibility of an innovative passive isolation strategy based on giant elastic metamaterials is numerically proved to be practical for civil structures. In particular, attenuation of seismic waves is demonstrated via finite elements analyses. Further, a parametric study shows that depending on the soil properties, such an earthquake-proof barrier could lead to significant reduction of the superstructure displacement.

Citta' e territorio: La formazione della citta' romana nell'ager gallicus

La presente ricerca affronta lo studio della formazione delle realtà urbane nell'area dell'antico Ager Gallicus, grossomodo corrispondente all'attuale territorio delle Marche settentrionali. Nel quadro della colonizzazione romana il fenomeno urbano rappresenta, infatti, l'elemento cardine nell'organizzazione di un territorio. Per tale ragione, si è scelto di condurre un lavoro finalizzato alla comprensione dei tempi e dei modi che portarono alla formazione dei municipi e delle colonie nella strutturazione romana del territorio, cercando anche di comprendere le scelte insediative alla base delle singole forme strutturali. L'analisi della genesi e dello sviluppo del fenomeno urbano nell'ager Gallicus ha come obiettivo ultimo l'approfondimento della conoscenza sulla colonizzazione e romanizzazione in area medio adriatica. La ricerca si articola in: uno stato dell'arte delle più recenti interpretazioni storiografiche; una sintesi sulle cosiddette “forme della conquista” (frequentazioni “precoloniali”, realtà santuariali, fondazioni coloniarie, realtà proto-urbane legate all'agro); una dettagliata e aggiornata schedatura storico-archeologica e urbanistico-topografica delle singole realtà urbane dell'ager Gallicus (le colonie di Sena Gallica, Pisaurum, Fanum Fortunae e Aesis, e i municipi di Forum Sempronii, Suasa e Ostra, e Sentinum); una parte conclusiva dove, mettendo a confronto gli elementi alla base della definizione urbana delle realtà esaminate, vengono delineati e sintetizzati i principali modelli di formazione delle città nell'ager Gallicus così individuati (fondazione coloniaria; fondazione coloniaria preceduta da una fase precoloniale nella forma di conciliabulum; nucleo di aggregazione precedente (conciliabulum) scelto quale polo di riferimento del popolamento sparso nel territorio al momento delle distribuzioni viritane; centro di servizio creato in funzione di assegnazioni di terre ai coloni). Infine, viene tracciato un quadro complessivo della romanizzazione dell'ager Gallicus, che, in estrema sintesi, si configura come un processo progressivo di occupazione del territorio rispecchiato dallo sviluppo stesso del fenomeno urbano, ma che si differenzia dalle aree limitrofe o dall'area cisalpina per alcune importanti dinamiche etnico-demografiche.

Measurement of LSP-induced residual stresses and fatigue life on thin-walled aluminium alloys specimens

This thesis work encloses activities carried out in the Laser Center of the Polytechnic University of Madrid and the laboratories of the University of Bologna in Forlì. This thesis focuses on the superficial mechanical treatment for metallic materials called Laser Shock Peening (LSP). This process is a surface enhancement treatment which induces a significant layer of beneficial compressive residual stresses underneath the surface of metal components in order to improve the detrimental effects of the crack growth behavior rate in it. The innovation aspect of this work is the LSP application to specimens with extremely low thickness. In particular, after a bibliographic study and comparison with the main treatments used for the same purposes, this work analyzes the physics of the operation of a laser, its interaction with the surface of the material and the generation of the surface residual stresses which are fundamentals to obtain the LSP benefits. In particular this thesis work regards the application of this treatment to some Al2024-T351 specimens with low thickness. Among the improvements that can be obtained performing this operation, the most important in the aeronautic field is the fatigue life improvement of the treated components. As demonstrated in this work, a well-done LSP treatment can slow down the progress of the defects in the material that could lead to sudden failure of the structure. A part of this thesis is the simulation of this phenomenon using the program AFGROW, with which have been analyzed different geometric configurations of the treatment, verifying which was better for large panels of typical aeronautical interest. The core of the LSP process are the residual stresses that are induced on the material by the interaction with the laser light, these can be simulated with the finite elements but it is essential to verify and measure them experimentally. In the thesis are introduced the main methods for the detection of those stresses, they can be mechanical or by diffraction. In particular, will be described the principles and the detailed realization method of the Hole Drilling measure and an introduction of the X-ray Diffraction; then will be presented the results I obtained with both techniques. In addition to these two measurement techniques will also be introduced Neutron Diffraction method. The last part refers to the experimental tests of the fatigue life of the specimens, with a detailed description of the apparatus and the procedure used from the initial specimen preparation to the fatigue test with the press. Then the obtained results are exposed and discussed.

Numerical analysis of the relation between interactions and structure in a molecular fluid

Coarse graining is a popular technique used in physics to speed up the computer simulation of molecular fluids. An essential part of this technique is a method that solves the inverse problem of determining the interaction potential or its parameters from the given structural data. Due to discrepancies between model and reality, the potential is not unique, such that stability of such method and its convergence to a meaningful solution are issues.rnrnIn this work, we investigate empirically whether coarse graining can be improved by applying the theory of inverse problems from applied mathematics. In particular, we use the singular value analysis to reveal the weak interaction parameters, that have a negligible influence on the structure of the fluid and which cause non-uniqueness of the solution. Further, we apply a regularizing Levenberg-Marquardt method, which is stable against the mentioned discrepancies. Then, we compare it to the existing physical methods - the Iterative Boltzmann Inversion and the Inverse Monte Carlo method, which are fast and well adapted to the problem, but sometimes have convergence problems.rnrnFrom analysis of the Iterative Boltzmann Inversion, we elaborate a meaningful approximation of the structure and use it to derive a modification of the Levenberg-Marquardt method. We engage the latter for reconstruction of the interaction parameters from experimental data for liquid argon and nitrogen. We show that the modified method is stable, convergent and fast. Further, the singular value analysis of the structure and its approximation allows to determine the crucial interaction parameters, that is, to simplify the modeling of interactions. Therefore, our results build a rigorous bridge between the inverse problem from physics and the powerful solution tools from mathematics. rn

Il dimensionamento delle sovrastrutture stradali non pavimentate

A comparison between main design methods for unpaved roads is presented in this paper. An unpaved road is made up of an unbound aggregate base course lying on a usually weak subgrade. A geosynthetic might be put between the two in reinforcing and separating function. The goal of a design method is to find the appropriate thickness of the base course knowing at least traffic volume, wheel load, tire pressure, undrained cohesion of the subgrade, allowable rut depth and influence of the reinforcement. Geosynthetics can reduce the thickness or the quality of aggregate required and improve the durability of an unpaved road. Geotextiles contribute to save aggregate through interaction friction and separation, while geogrids through interlocking between his apertures and lithic base elements. In the last chapter a case study is discussed and design thicknesses with two design methods for the three possible cases (i.e. unreinforced, geotextile reinforced, geogrid reinforced) are calculated.