COURSE - Mechanics of heterogeneous materials: From homogenization theory to strain localization phenomena
Ottobre 24, 2024, at 2:00pm-5:30pm and Ottobre 25, 2024, at 9:00am-12:30pm
The heterogeneous nature of materials like fiber reinforced composites and grains in metallic polycrystals can be used as an asset in the design of optimized microstructures. Averaging methods will be described for stress, strain and energy in order to predict the effective properties. The proposed illustrations deal with elasticity of composites and plasticity of crystals. The concept of representative volume element for random microstructures will be presented. Computational homogenization can be used to predict the failure of materials by strain localization in the form of shear bands. Concepts of loss of uniqueness and loss of ellipticity will be applied to predict shear banding in elastic-plastic dense and porous materials. Finite element simulations of strain localization are characterized by a spurious mesh-dependence of the results. The regularization of these problems requires the introduction of internal lengths in the constitutive model. The strain gradient plasticity theory will be presented and used for this purpose.
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COURSE - Seismic Safety and Sustainability: Next Generation of Low-Damage Concrete and Timber Buildings
October 10, 15, and 23, 2024 at 10:00am-1:00pm
The 2010-2011 Canterbury (New Zealand) earthquake sequence has highlighted the severe mismatch between societal expectations over the reality of seismic performance of modern buildings. Life Safety is not enough for modern societies; a paradigm shift in performance-based design criteria and objective towards Damage Control, or low-damage, design philosophy and technologies is urgently required. The ‘bar’ has been raised significantly with the request to fast track the development of what the general public would refer to as the “ultimate” earthquake resisting (towards an “earthquake proof”) building system, capable of sustaining the shaking of a severe earthquake basically unscathed. This short course will provide an overview of recent advances through extensive research, development and implementation, carried out in the past twenty-five years, of an integrated low-damage building system including the skeleton of the superstructure and the non-structural components. Examples of real on site-applications of such low-damage technology in New Zealand and worldwide, using concrete, timber (engineered wood), steel or a combination of these materials, and featuring some of the latest innovative technical solutions developed in the laboratory will be presented as comforting example of successful transfer of performance-based seismic design approach and advanced technology from theory to practice in line with the broader objective of Building Resilience.
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SEMINAR - 3D Concrete Printing: Recent Advancements and Future Trends
September 9, 2024, 11:00am-12:30pm
3D concrete Printing (3DcP) is a digital construction technology to transform the construction industry by replacing the currently used casting-in-the-mould methods with digitally controlled layer-by-layer additive-construction technology. 3DcP removes the need for formwork (temporary moulds used for casting concrete), thus eliminating a very significant source of waste from construction. Further, the use of standard formworks limits the creativity of architects and options to build varied geometries unless expensive bespoke formworks are produced. This presentation covers the recent advancements in 3DcP technology and the printing process. It also provides information about the printable material requirements and formulations. Further, experimental and numerical techniques to model the pumping and extrusion process of printable concrete will be discussed.
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SEMINAR - The Mission to Apophis
July 16, 2024, 4:40pm-5:45pm
We will present the case for our one great shot to meet asteroid Apophis in 2029. In 2004, an asteroid the size of 5 football fields was discovered and thought to be on a path to impact Earth. It was named Apophis, after the god of Chaos, for its potential to cause widespread global devastation. Subsequent observations have shown that Apophis will barely miss hitting Earth, but on April 13, 2029, it will come so close to Earth’s surface that more than a billion people will see it shinning as brightly as a star moving rapidly across the sky with the naked eye. The event will make the closest Earth flyby of an asteroid in recorded history. While some billion will witness this once-in-a-millennium event, our mission has set sight on harnessing the opportunity to conduct a rare science expedition that would map the surface and interior of Apophis to return data critical to the Earth’s planetary defense. This type of science experiment is only possible once in a lifetime when (1) the subject of observation has been identified early enough for response, (2) is an object of great interest due to its size and trajectory in relation to Earth, and (3) most importantly, coming close enough for our constellation of spacecraft to launch in time to rendezvous with it. Our mission will return data on Apophis’s interior structure, changes in its surface formation, and a photo of the asteroid with Earth in the background.
The mitigation of a future threat is a global issue that requires immense advanced coordination and activation. A rendezvous with Apophis will be a defining moment in our collective history as a small team of scientists, technologists, explorers, and risk takers prepare humanity to meet Chaos on our own terms by demonstrating that we are equipped to defend our planet against future asteroids that threaten our existence.
With the world watching, are we prepared to meet the moment?
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COURSE - Ultrasonic bulk and guided wave propagation in classical and non-classical continua
July 17 - 10:00am-1:00pm; July 18 - 4:00pm-7:00pm; July 19 - 10:00am-1:00pm; 2:00pm-5:00pm
PART I: ULTRASONIC BULK AND GUIDED WAVE PROPAGATION (A. Pau). Being able to handle wave propagation is essential to the understanding of nondestructive evaluation techniques, which enable location and measurement of defects in structures, evaluation of constitutive material constants, and identification of the state of stress. This short course covers selected problems of wave propagation in structures, that is, waves in strings, bulk waves in 3D solids, guided waves, acoustoelasticity, and their application to the solution of materials characterization and image reconstruction problems.
PART II: NON-LOCAL CONTINUOUS FORMULATIONS FOR MATERIALS WITH MICROSTRUCTURE AND WAVE PROPAGATION (P. Trovalusci). Focus will be on non local continua with internal lengths and dispersion properties in wave propagation. Non-local continuous formulations for materials with microstructure, including topics such as: discrete-to-scale dependent continuum models, deformations, strain measures, stress measures, balance laws, constitutive equations, thermodynamic restrictions, with applications to composites and masonry, will be covered.
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SEMINAR - Real-time Hybrid Simulation and Application Towards Enhancing Multi-Natural Hazard Civil Infrastructural Resiliency
July 12, 2024 - 3:00pm-4:30pm
Stakeholders are demanding that the performance of the built civil infrastructure be more resilient to natural hazards in order to reduce their impact on society. Performance-based engineering is a means to attempt to meet performance objectives associated with prescribed levels of hazards. A viable technique to meet validation requirements for performance-engineered structural systems is to use real-time hybrid simulation to perform cyber-physical experiments. The complete system is involved in these simulations, where selected components of the system are modeled physically while others are modeled numerically using computational models. The modeling of the former in the physical domain is required because accurate computational models do not exist for these components. In such studies the response modification devices can be coupled to a system that is subjected to a prescribed hazard with a specific return period, enabling system performance under prescribed levels of realistic hazard demands to be established. The talk will present results from recent efforts that the presenter and his research team have completed to advance large-scale multi-directional real-time hybrid simulation. Topics of the talk include an overview of the development of model-based unconditionally stable dissipative explicit direct integration algorithms, explicit state-determination force-based fiber elements, and adaptive servo-hydraulic actuator control algorithms. The real-time integrated control IT architecture used to implement these develops will also be presented. The talk will conclude with applications of these developments to perform real-time hybrid simulations of nonlinear structural systems subjected to earthquake and wind hazards, including extensions to offshore wind turbines, aeroelastic response of tall buildings, and simulations with soil-structure interaction involving machine learning.
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SEMINAR - Structural Reliability under Multiple Loads and Disaster Actions
July 9, 2024 - 10:00am-11:30am
The reliability analysis of engineering structures under multiple loads and disaster actions is an unsolved problem in the development of the reliability research. Starting from the mathematical description of the principle of load coincidence, this lecture discusses in detail the analysis method of the structural response under multiple loads and disaster actions. By introducing the physical synthesis method of reliability analysis, a new approach to the structural reliability under multiple loads and disaster actions is suggested. Some specific research examples and engineering applications are presented. The development showed in the lecture make known that the third generation of structural design theory has become a realistic option in the engineering practice.
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COURSE - Fundamentals of variational calculus
July 1, 2, and 5, 2024 - 10:30am - 1:30pm
The essentials of the fundamentals of the calculus of variations will be presented, together with some examples, with particular attention to applications to mechanics.
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COURSE - Failure and Instability in Geomaterials and Geosystems
June 10, 2024, 3:00pm-7:00pm, June 11 and 12, 2024, 10:00am-2:00pm
This 3-day course introduces, at the post-graduate level, the basic principles of material stability analysis, with specific reference to geomaterials such as soil and rock. First, an introduction to the definition and use of different metrics of material instability is given, including second-order work and controllability indices. Analytical techniques to differentiate localized and diffuse failure are then discussed, along with an examination of the implications of shear banding for the numerical analysis of geotechnical problems and examples of possible computational remedies. Afterwards, diffuse instabilities of the liquefaction type and the role of the pore fluids on their initiation are addressed, stressing the role of transitions from unsaturated to saturated conditions. Finally, the relevance of geomaterial instability in the context of landslide geomechanics is addressed. Examples of application spanning from rapid shallow landslides of the flow type to deep-seated creeping landslides are shown, with the goal to highlight the feedback between material instability, inelastic deformation, and the temporal dynamics of landslide motion.
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SEMINAR - Seismic-Resilient Damage-Free Self-Centring Steel Structures
May 24, 2024, 2:30pm-4:00pm
Seismic design methods suggested by current design codes/guidelines and conventionally applied worldwide are based on energy dissipation related to construction damage, hence leading to large direct and indirect losses in extreme events. This strongly affects the overall resilience of affected communities, especially when the damaged structures include strategic facilities such as hospitals and fire stations that must remain operational in the aftermath of a damaging earthquake. To overcome this issue, several recent research works investigated innovative solutions for the design of seismic-resilient structures, chasing the objectives of minimising both seismic damage and repair time, hence allowing the definition of structures able to go back to the undamaged, fully functional condition in a short time. The seminar will present some of the recent research advancements, including experimental, numerical, analytical, and probabilistic studies on some novel technologies allowing the definition of such damage-free self-centring structures.
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COURSE - Mechanical metamaterials: conceptualization, analysis and design
May 23 and 24, 2024, 9:30am-12:30pm
The endless development of physical-mathematical formulations, powerful analytical methods and computational techniques, combined with recent extraordinary advances in high-technology microengineering and high-fidelity manufacturing, are paving the way for the emergence of an entirely new generation of microstructured materials, known as mechanical or acoustic metamaterials. The macroscopic dynamic behavior of mechanical metamaterials can be governed by appropriately designing the topology, compositeness and architecture of the periodic cellular microstructure. Proper optimization of microstructural design can enable extreme or exotic performance to be achieved, unattainable by natural or traditional synthetic materials. Consequently, the advent of mechanical metamaterials opens up completely new and revolutionary possibilities in the customization of functional and tunable systems with fascinating applications in traditional and emerging engineering fields, including shock absorption, noise cancellation, wave focusing, energy harvesting, vibration shielding and sonar invisibility, among many others. The objective of this short course is to provide an updated basic knowledge on mechanical metamaterials, organized in the following topics: 1. Introduction to mechanical metamaterials, 2. Free wave propagation in periodic materials, 3. Mechanisms of formation and manipulation of the frequency band structure, 4. Methods of wave propagation analysis in the time and frequency domain, 5. Mechanical metamaterials for sound insulation and vibration protection, 6. Dynamic phenomena in nonlinear metamaterials.
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COURSE - Some topics in continuum mechanics: crystals and foams
May 15, 2024 4:00pm-6:00pm, May 16, 2024 10:00am-12:00pm, 4:00pm-6:00pm, May 17, 2024 10:00am-12:00pm
Continuum mechanics has a long history of successes and has given fruits in manifold areas of technics and science. In particular, it has provided a paradigm to model various phenomena of the physical world as they are perceived at the macroscopic level, prompting the study of specific mathematical problems, general solutions and affordable approximation techniques. In the last part of the past century, though, within the continuum mechanics community there caught on a special interest for themes new and different. In particular, the scrutiny of reality became finer and the attention started being addressed to certain microscopic aspects of the mechanics of materials that do have effects at the macroscopic level. An important contribution to this change of perspective was given by an article of Ericksen, published in 1977, that highlighted the role of molecular elasticity and stability in certain anelastic behaviours of materials. This change of perspective has had various consequences. In particular, it has undermined some cornerstones of continuum mechanics, drawing attention to some of its limits. At the same time, it has broadened the horizon and opened the way to the study of new problems such as the modeling of a new class of materials (e.g. cellular materials, honeycombs, foams, nano-materials) and the study of growth in living tissues. The aim of these lessons is to give an account of some topics that have been faced within the framework of this change of perspective.
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COURSE - An innovative approach to static and dynamic topology optimization with practical applications
May 9 and 10, 2024, 9:00am-1:00pm
An innovative approach to topology optimization is presented that is based on the minimization of a proper norm of the input/output transfer matrix G. The singular value decomposition (SVD) of G is shown to be the key ingredient of the proposed optimization strategy that applies to static and dynamic topology optimization, with nearly no modifications. Alongside the theoretical derivations, the class is introduced to the coding of the proposed approach in the Matlab environment as far as the static regime is concerned, whereas hints are given for the extension to dynamic response. The optimization of exoskeletal systems that minimize the response of 3D framed structures to horizontal environmental actions is one of the results of practical interest that are achieved.
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COURSE - Isogeometric analysis: recent advances with applications to complex and coupled problems
April 18, 2024, 4:00pm-6:00pm and April 19, 2024, 11:00am-1:00pm
Isogeometric Analysis (IGA) is a successful simulation framework originally proposed by T.J.R. Hughes et al., in 2005, with the aim of bridging Computational Mechanics and Computer Aided Design. In addition to this, thanks to the high-regularity properties of its basis functions, IGA has shown a better accuracy per degree-of-freedom and an enhanced robustness with respect to standard finite elements in many applications - ranging from solids and structures to fluids, as well as to different kinds of coupled problems - opening also the door for the approximation in primal form of higher-order partial differential equations.
This short course aims at providing a concise introduction of the basic isogeometric concepts and at presenting an overview of some recent advances in IGA with a special focus on complex and coupled problems where the characteristics of IGA seem to be of great advantage. In particular, applications that will be discussed include, among others, the simulation of fluid-structure interaction in different contexts like, e.g., biomechanical problems, studies on the effect of mechanically-induced stresses on prostate cancer growth, thermo-mechanical simulations of additive manufacturing processes, electro-mechanical simulations for biological tissues, and the use of phase-field modeling for fracture and topology optimization problems or for predicting the polarization evolution in ferroelectric materials.
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COURSE - Random Vibrations in Offshore Structures
April 8, 2024, 3:00pm-6:00pm, April 9, 2024, 10:00am-1:00pm
In the course, elements for random vibrations in the context of structural modeling and design will be given. The course is divided into two main parts. First, fundamentals of stochastic processes in time and frequency domain are given. For instance, random variables and processes are discussed together with Fourier transforms and Spectral Density Function definitions. Second, design to avoid structural failures due to random vibrations will be discussed such as level crossing analysis and fatigue criteria. Each course section will provide theoretical as well as practical aspects of the topics with reference to current design regulations.
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SEMINAR - Monitoring the structural health and estimating the remaining strength of main cables of existing suspension bridges
March 27, 2024, 10:00am-12:00pm
Suspension bridges have become essential elements in the transportation network of major metropolitan areas. However, some of these bridges are reaching a service life of over 100 years. Main cables are the most critical elements for the overall safety of such structures; however, it is very difficult to inspect and assess the condition of a main cable of a bridge that has been in service for many years. Currently, all agencies responsible for the maintenance of suspension bridge cables base their plans mainly on previous experiences and, when possible, on visual inspections.
In this presentation, a study focused on the development of a corrosion monitoring system for main cables of suspension bridges is presented. These sensors measure corrosion rate as well as quantities like temperature and relative humidity that are directly correlated to corrosion activity. The results show that the selected sensor network system was successful in providing information on the interior environment of a main cable, helping to understand the conditions in which main cables of suspension bridges operate. Field testing of the developed monitoring system on the Manhattan Bridge in New York City was used to determine the functionality of the system in in-service conditions. In addition, having the possibility of measuring temperature and relative humidity inside the cross-section also allowed us to test the effectiveness of the cable dehumidification strategy. The information provided by sensors embedded in the main cable has been very valuable to understand the mechanical behavior of such cables when subjected to extreme temperature (e.g. external fire) and it has been used to estimate the remaining strength of a cable in service.
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SEMINAR - Vibration monitoring as a tool for rapid damage assessment in bridges
March 21, 2024 3:00pm-5:00pm
In this seminar, different methods that can be used for a rapid evaluation of the structural condition of bridges and buildings are discussed and validated using measurements of the dynamic response, both from numerical simulations and from field tests. Falling into the category of “data based” methods, such methods only need as input the time histories of the structural response measured at different locations on the structure and, when possible, in the case of seismic ground motion, the time histories of the ground acceleration, without any information on the geometry or mechanical characteristics of the structure.
Special attention will be given to methodologies that can be framed within a statistical pattern recognition framework, ideal for machine learning applications. Such methodologies focus on the recognition of certain patterns in the behavior of damage sensitive features, features that can be easily extracted from the time histories of the structural response. Quite popular in the field of speaker recognition, cepstral coefficients extracted from the time histories of the structural acceleration through simple digital signal processing are used as damage sensitive features, through the use of a Time-Delay Neural Network and of Generalized Autoencoders. These methodologies will be validated using field data from a real bridge (the Z24 bridge) that, before being demolished, went through an extensive monitoring campaign with progressive imposed damage.
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COURSE - Issues of Continuum Thermodynamics
March 13, 14, and 15, 2024 - from 4:00pm to 6:00pm
This course is addressed to mathematical modelers-to-be who are reasonably familiar with the basic concepts of Continuum Physics for as much as is necessary to deal with purely mechanical phenomena but perhaps less familiar with the manner thermal phenomena are or should be dealt with. The attendees may find perusal of my booklet [1] of some help. The intended contents are summarized below.
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COURSE - Combining Molecular Mechanics and Continuum Thermo-Mechanics
February 26th 2024 3:30pm-5:30pm, February 27th 2024 4:00pm-6:00pm, February 29th 2024 3:30pm-5:30pm
In this short course, I will introduce and discuss the fundamentals of molecular mechanics and of continuum (thermo-)mechanics, presenting them in a common framework. After bringing to the fore the complementary strengths and weaknesses of continuum field theories on one side and molecular dynamics on the other side, I will present the basics of a new conceptual and computational framework in which the macroscopic and the microscopic components, while evolving in parallel, are coupled cell-wise on an intermediate, mesoscopic length-time scale, thus enhancing their complementary strengths and mitigating their respective weaknesses.
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SEMINAR - A Journey into Innovation and Vision
February 23, 2024 at 3:00pm
Explore the architectural genius of Dante Bini, a pioneer who redefined the boundaries of modern construction with his bold vision and revolutionary technique. Delve into his captivating world, uncovering the roots of his inspiration, his most iconic projects and the lasting impact he has had on contemporary architecture. Renowned for his innovative approach to construction, Bini's work has enabled the realization of bold and futuristic structures. Through his patented technique, the Binishell, he has shown that it's possible to create eco-friendly, efficient, and aesthetically stunning buildings using local materials and harnessing the power of nature itself. We will trace the evolution of Bini's architectural vision, from early experiments to the realization of monumental works worldwide. Sharing compelling stories of challenges overcome and extraordinary successes, this journey offers an insider's view into the creative mind of one of the great innovators of our time.
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COURSE - Reverse Engineering: fundamentals, models, monitoring, digital twins
February 20, 22, and 23, 2024 at 10:00am-1:00pm
Reverse engineering (or sometimes back-engineering) is a process that is designed to extract enough data from a product or a construction and then to be able to reproduce that product or to renovate it. In this context, this 3 days course is aimed at proposing a general framework for interacting methodologies used to digitally describe existing construction for different aims such as structural safety evaluation, management, new functionalization, monitoring and retrofitting. Starting from basics in structural dynamics the flow of data coming from vibration measurements and their treatment is presented as an archetypal use of observations of the given product. The key ingredients of structural identification are introduced such as: principles of direct and inverse dynamics, output-only parametric identification and strategies of model updating. Then, issues related to the creation of advanced integrated modelling are considered, such as: 3D point cloud to building information modelling (3DPCM-to-BIM) and building information modelling to finite element modelling (BIM-to-FEM). Finally, innovative use of data coming from different sources (vibration measurements, image processing, satellite interferometry) within an integrated monitoring environment are presented as fundamental steps for the realization of digital twins of products and constructions in changing environment.
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SEMINAR - Size dependent behaviour of intact rocks: recent findings and future direction
February 19, 2024, 11:00am-12:00pm
The design of structures on or within rock masses requires an estimate of the strength of the intact rock blocks within the mass. These blocks of rock can be many orders of magnitude greater in size than laboratory samples typically tested. The properties obtained from these samples must therefore be ‘scaled’ to equivalent field values. This presentation talks about current methods for scaling strength and other rock properties and, in lieu of noted limitations, presents a constitutive model for intact rock that incorporates size effect. It also includes recent findings and works published regarding size or scale effects in intact rocks under various loading conditions.
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COURSE - Finite Element Method
February 12, 14, 2024 at 11:00am-2:00pm, February 16, 2024 at 11:00am-2:00pm, 3:00pm-6:00pm
This class introduces the fundamentals of the Finite Element Method (FEM) to handle the numerical solution of general mechanical problems, with special reference to the structural framework. The most and widely adopted numerical codes rely on the classical displacement-based formulation, then, this is illustrated in detail. Also, two- and three-field mixed FE approaches are briefly introduced. The main FEs adopted to solve 1D, 2D and 3D continuum problems are illustrated, that is truss, frame, solid, plate and shell FEs are described. Some hints concerning nonlinear formulations, numerical pathological issues and solution strategies are finally given.
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COURSE - Information literacy skills, research strategies and sharing your findings
February 5, 2024 at 10:00am-12:00pm, February 6, 2024 at 3:30pm-5:30pm
This course is intended as an introduction to using academic literature in young academic’s research. The scope is to introduce Ph.D. candidates to the principles and practice of Information Literacy as applied to research, develop those skills which will enhance the quality of their research output, expand their career opportunities in a knowledge-based society and create awareness of both quantitative and qualitative measurement tools. In a series of hands-on workshops, candidates will learn to build their research skills, improve their search strategy, and carry out a literature review.
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COURSE - Numerical modelling of geomechanical problems
January 23, 25, 26, 29, and 31, 2024 – 10:00am-1:00pm
This 15-hour course is designed to provide a comprehensive understanding, at the post-graduate level, of the key aspects of saturated soil modelling using the finite element method. It begins by introducing the field equations that govern the interaction between soil skeleton and pore fluid under static conditions, followed by their finite element discretization and solution. The course explores relevant challenges in practical applications, including considerations such as 2D versus 3D schematization, initial and boundary conditions, staged construction, and soil-structure problems, illustrated with practical examples. The course also delves into the implementation of soil constitutive laws at the level of Gauss integration points, encompassing both common explicit and implicit numerical algorithms. In the final session, the scope of the governing equations is expanded to cover dynamic conditions, offering insights into addressing earthquake geomechanical problems.
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COURSE - An introduction to the mechanics of soils
January 16, 17, and 18, 2024 - 10:00pm-4:30pm
This 3 days course is aimed at introducing, at the post-graduate level, the basic principles of the mechanics of soils by discussing some of their experimental features and constitutive modelling strategies, with particular emphasis to clayey materials. The fundamental field equations for a two-phase medium are first derived, followed by an overview of typical experimental results and their interpretation in the frame of Critical State Soil Mechanics.
The key ingredients of plasticity theory are then introduced, first under 1D conditions and then generalised to 3D ones, aiming at providing the general theoretical setting then adopted to illustrate a wide class of plasticity-based models for soils, ranging from standard perfectly plastic ones to more advanced mixed-hardening multi-surface formulations.
Finally, an alternative constitutive approach based on thermodynamics with internal variables is introduced and its merits are illustrated with reference to different forms of elasto-plastic coupling of soils.
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