COURSE - Recent developments in the design of underground constructions
December 5, 6, 7,12,13,14,15,16, 20 - 2022
Il corso propone un approfondimento di alcuni temi di notevole interesse per l’analisi del comportamento delle opere in sotterraneo e della loro interazione con l’ambiente, sia durante le fasi costruttive sia durante l’esercizio. Il sempre più intenso sviluppo delle reti infrastrutturali, anche in contesti complessi dal punto di vista geologico, idrogeologico e geotecnico, e l’innalzamento degli standard progettuali richiedono infatti la messa in campo di competenze specialistiche non ancora diffuse nella pratica tecnica e spesso ancora oggetto di studi e ricerche. Le prime lezioni sono dedicate a richiamare le conoscenze di base del settore, dalla caratterizzazione geotecnica per la progettazione di gallerie alle principali soluzioni analitiche per la valutazione dello stato tensio-deformativo nell’intorno del cavo e per l’analisi dell’interazione con le opere di rinforzo e sostegno. Vengono quindi approfonditi gli approcci tradizionali e più avanzati per il progetto di gallerie nell’ambito dello scavo in tradizionale e meccanizzato mediante macchine TBM. Infine, sono trattati, sotto forma di seminari dedicati, i seguenti argomenti: verifiche sismiche, interazione pendii-gallerie, verifiche a fuoco, effetti indotti dallo scavo di gallerie superficiali e gallerie sotto falda
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COURSE - An introduction to the mechanics of soils
November 22, 2022, 09:30am-11:30am, 12:30pm-1:30pm, 2:30pm-4:00pm - November 23-24, 2022, 10:00am-12:30pm, 2:00pm-4:00pm
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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COURSE- Seismic Safety and Sustainability:Next Generation of Low-Damage Concrete and Timber Buildings
November 15-17-18, 2022 - 10:00am-1:00pm
The severe socio-economic impact of recent earthquake events have further highlighted, on one hand, the severe mismatch between societal expectations over the reality of seismic performance of modern buildings, while confirming, on the other hand, the crucial need for a coordinated seismic risk reduction plans at a national level.
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 increased awareness by the general public/tenants, building owners, territorial authorities as well as insurers/reinsurers, of the severe economic impacts of moderate-strong earthquakes in terms of damage/dollars/downtime has indeed stimulated and facilitated the wider acceptance and implementation of cost-efficient damage-control, or low-damage, technologies.
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 years, of an integrated low-damage building system including: the skeleton of the superstructure, the non-structural components and the interaction with the soil/foundation system.
Examples of real on site-applications of such technology in New Zealand, 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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COURSE - Introduction to Nano-mechanics: Continuum Modeling and Atomistic Simulation
November 9-10-11, 2022 - 10:00am - 1:00pm
Nanotechnology deals with design, characterization and production of structures at the nano-scale. It has a broad application in different scientific sectors encompassing engineering, the automotive industry, renewable energy generation, tissue engineering and information technology. Nano-mechanics is one of the essential sub-fields of nanotechnology, focusing on the mechanical evaluation of nano-structures and nano-systems. In nano-mechanics, besides the experimental efforts, which may be formidable and expensive, there are three main approaches: (1) continuum modelling, (2) atomistic modelling, generally admitted as numerical experiments and (3) multi-scale modelling, which hybridizes the accuracy of atomistic simulation and efficiency of continuum description. In this course, first, a general overview of nano-mechanics and modelling approaches at nano-scale will be provided. The second part will present an introduction to the molecular dynamics (MD) simulations as an atomistic modelling technique. In the third part, the attendees will be acquainted with the implementation of MD in Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) open-source software.
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COURSE - Soft Mechanics and Instabilities
October 25, 26, 27, and 28, 2022 - 12:00pm-1:00pm, 2:00pm-4:00pm
Mechanics of soft materials and structures present many interesting aspects from both the point of view of the modeling and the applications. One aspect which will be stressed in the course is related to the large changes in shape which can be expected due to a class of the external stimuli which include mechano-chemical actions.
Changes in shape can be smooth or not, with respect to some key control parameter, which depends on the specific problem; when they occur instantaneously, an instability process has taken place.
The aim of the short course is to deal with a few problems characterized by instability patterns in soft structures. The course will include: introduction to fundamentals of continuum mechanics, analysis of stress-diffusion problems, introduction of some prototypes of stability loss, analysis of elastic instabilities in soft polymer-based structures driven by chemical and/or mechanical control.
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SEMINAR - Thrust Network Analysis of Masonry Vaults
October 14, 2022 - ore 4:00pm-4:45pm
We address the Thrust Network Analysis (TNA), i.e. the methodology for modeling masonry vaults as a discrete network of forces in equilibrium with gravitational loads, first contributed by O’Dwyer and fully developed by Block and coworkers. Reducing the bias by the quoted authors in favor of a graphical interpretation of the method, we reformulate the original version of the TNA in order to significantly enhance the computational performances. The proposed reformulation of the TNA is also extended in a twofold manner, i.e. by including horizontal forces in the analysis and holes or free edges in the vault. Furthermore, the coefficient matrices entering the solution scheme are obtained by assembling the separate contribution of each branch, thus avoiding ad hoc node numbering and branch orientation required by alternative implementations. Numerical examples, some of which referred to vaults having a particularly complex geometry, show the effectiveness and robustness of the proposed approach in assessing the safety conditions of existing masonry vaults or in designing new ones.
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SEMINAR - Recent Advancements in the Modeling of Hysteretic Phenomena for Mechanical Systems and Materials
October 14, 2022 - ore 5:15pm-6:00pm
The number and nature of hysteretic responses typically exhibited by mechanical systems and materials are so huge that their modeling and identification are usually carried out on an ad-hoc basis. Thus, with the aim of proposing a unified approach to the modeling of rate-independent hysteretic behavior, we first perform a detailed classification of complex generalized force–displacement hysteresis loops, ranging from the asymmetric, pinched, S-shaped, flag-shaped ones to those obtained by their arbitrary combination, since they typically span the vast majority of loops obtained experimentally. Subsequently, we formulate a novel rate-independent hysteretic model, having an exponential nature, that offers a series of advantages over other hysteretic models available in the literature. Indeed, it adopts closed form expressions for evaluating the output variable, with important benefits in terms of computational efficiency and implementation ease, and it allows for an uncoupled modeling of the generic loading and unloading phases by means of two different sets of eight parameters. In addition, it
requires the use of a simple identification procedure thanks to the clear theoretical and/or experimental interpretation of the adopted parameters. The accuracy of the proposed model is experimentally and numerically validated and its computational efficiency is demonstrated. In particular, the experimental validation is carried out by reproducing four different types of complex experimental hysteresis loops retrieved from the literature, whereas the numerical validation is performed by running some nonlinear time history analyses on a single degree of freedom mechanical system and comparing the results with those obtained by using a modified version of the celebrated Graesser–Cozzarelli model.
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SEMINAR - Out-of-plane instability of ductile reinforced concrete structural walls: Failure mechanism and key design recommendations
September 26, 2022 from 5:00pm to 6:00pm
Following observations of out-of-plane instability in slender ductile structural walls in some recent earthquakes, this mode of wall failure has been and is being investigated by several research groups. Analytical, numerical and experimental investigations have been conducted to study this failure mechanism as well as its controlling parameters. Both singly reinforced and doubly reinforced concrete walls have been studied under uni-directional and bi-directional loading. A simplified approach making use of concrete columns representing boundary zones of rectangular walls has also been used to reduce the computational and experimental costs of the research programs. This presentation provides a state-of-the-art on the research conducted on this failure mechanism and elaborates on the sequence of events resulting in its development in structural walls, including the effect of governing parameters such as wall section thickness, length, axial load, and longitudinal reinforcement ratio. Suitability of the existing requirements in the New Zealand Concrete Design Standard (NZS 3101:2006-A3) for prevention of this failure mechanism is also evaluated and several key design recommendations are discussed in light of the numerical and experimental studies conducted at the University of Canterbury.
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COURSE - Pile foundations under seismic loading
18, 20 and 21 July, 2022 - 2:30pm-5:30pm, 10:00am-1:00pm, 11:00am-1:00pm
Pile foundations are the most common deep foundations used around the world to transfer super-structure loads into competent soil strata, particularly when poor soil strata exist at the ground surface. Many buildings in the seismic regions of the world are supported on pile foundations and therefore experience strong seismic loading particularly if the ground suffers liquefaction. It is often very difficult to investigate the performance of pile foundations under such conditions.
In this course, we will cover the use of dynamic centrifuge modelling to investigate the seismic behaviour of pile foundations, particularly when soil liquefaction occurs. By using the experimental data from centrifuge tests, we will discover the failure mechanisms that can occur in single piles and in pile groups. We will look at the load the load transfer mechanisms that can occur once liquefaction of soil sets in and also the settlement of piles following soil liquefaction. We will estimate the amount of settlement that pile foundations can suffer.
Overall, this course should give you an overview of the design of pile foundations in liquefiable soils.
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COURSE - Ultrasonic wave propagation in classical and non-classical continua. Applications to material characterization, damage imaging and stress monitoring
July 12-14-15, 2022 at 3:00pm-5:00pm
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.
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COURSE - Elements of dynamic identification of structures: general issues and applications
June 22 and 24, 2022, 10:00am-1:00pm
The course deals with the peculiar aspects of the structural identification of existing buildings, taking into account both the notional issues and the related practical implications. Attention will be focused on methods encompassing dynamic data. The problems arising in this context have an inverse nature, compared to the classic direct problems of the dynamics of structures, and present some specific ‘pathologies’. These may be related to the non-uniqueness of the solution or the lack of continuous dependence of the solution on the input data. During the course we will address some of these aspects, with reference to both simple structural models and mechanical systems of greater complexity and interest in engineering applications. The aim of the course is twofold: to consolidate the basic knowledge on structural identification issues, and to stimulate interest towards research topics belonging to this area.
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COURSE - Damage Mechanics and Modelling for Materials and Structures
May 26, 2022 - 11:00am-2:00pm, May 27, 2022 - 10:00am-1:00pm,
This class introduces the fundamentals of damage mechanics and modelling procedures to describe degrading processes evolving at material and structural level. The main damage model families presented in literature are illustrated, specially focusing on those developed for brittle like materials. Also, the coupling with plasticity formulations is introduced, and isotropic and anisotropic formulations are referred to. Some hints concerning localization problems related to strain softening behavior and pathological mesh dependency of the finite element solutions are given, together with the main regularization techniques. Then, the mechanics of damaging interface is treated, illustrating the modelling approach which accounts for the interface opening in mode I, mode II and mixed mode. Moreover, the unilateral contact is considered, and the possible frictional and interlocking effects are described. Finally, structural problems in presence of degrading processes are shown.
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COURSE - Analysis and optimization of the dynamic response of linear structures and systems
May 18, 2022 from 4:00pm to 6:00pm and May 19, 2022 from 9:00am to 1:30pm
This course aims to provide a rational and rigorous procedure for the optimal design of linear structures and systems in dynamic regime. After the student is acquainted with the two main pillars on which the suggested design strategy rests, i.e.:
− Static topology optimization (among the very many available approaches we shall follow Sigmund’s formulation and implementation),
− An abstract system-theoretic view of dynamic systems that is mainly based on transfer function matrices in the frequency (Fourier and Laplace) domain,
a possible extension of static topology optimization to structures and systems experiencing dynamic effects is presented. The main ingredient is the 𝐻∞-norm of the system transfer function that is discussed in much detail. Some insight into programming issues in Matlab is given and a few representative numerical results are introduced and discussed on.
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SEMINAR - Structural behavior of masonry walls with soft layers
May 13, 2022 - 3:30pm - 4:30pm
A numerous series of static-cyclic shear tests on masonry elements (triplets), wallettes and full-scale unreinforced masonry (URM) walls with soft layer membrane placed in the bed joint to induce sliding have been performed during the last ten years at ETH Zurich within several research projects on the seismic behavior of unreinforced masonry walls with such layers. Specimens were constructed using typical perforated Swiss clay and calcium-silicate blocks and standard cement mortar. As a soft layer type, the five types were considered (rubber granulate, cork, cork-rubber granulate, extruded elastomer and bitumen). In order to develop the most suitable joint in the first phase the specimens were tested placing the soft layer in the mortar joint or between the mortar and the blocks. Based on the results, the so-called multi-layer bottom bed joint, which comprises a core soft layer protected by two layers of extruded elastomer and placed in the middle of mortar joint, was developed. As a core soft layer, the four-layer types were considered: rubber granulate, cork, cork-rubber granulate and bitumen. The following testing phase was aimed at choosing the most suitable core soft layer – rubber granulate. The final testing phase comprised five tests on story-high URM walls with rubber granulate core soft layers performed to investigate the influence of the size, the pre‐compression level and the aspect ratio on the seismic behavior of URM walls with a multi‐layer bed joint. An overview of the mentioned experimental work and corresponding analytical models will be presented. In addition, the short summary of the major findings of other research topics of the structural masonry group: deformation capacity of structural masonry, hybrid testing of masonry, advanced measurement technics, and reliability of structural masonry will be presented.
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COURSE - Virtual element Method (VEM) for Fracture Mechanics/Elements of Programming with Python and Applications with VEM
April 20 and 22, 2022 - 9:00am - 11:00am / 3:00pm - 5:00pm
In the last 10 years, a new finite element methodology, the virtual element method (VEM), has been proposed by Brezzi, Beirao da Veiga and coworkers. The VEM is more flexible than standard FEM, as it is possible to discretize the domain by polygons characterized by any number of edges, without constraints. Moreover, it has also been proved that VEM presents several advantages with respect to classical FEM, such as ability to accurately deal with complex geometries, flexibility in mesh generation, no need of a parent element, easy polynomial degree elevation, very good performances for distorted meshes.
The lectures are devoted to the development of a virtual element method with application in fracture mechanics. The basic concepts of the VEM and the construction of all operators involved in the construction of the mathematical formulation will be explained during the course. Some detail concerning the VEM implementation in a Python framework will be given in order to enable the course participants to implement a virtual element. Then, a procedure for reproducing the nucleation and propagation of fracture in 2D cohesive media, combining the virtual element technique with a splitting methodology and a minimal remeshing procedure will be discussed and possible applications will be illustrated.
Prerequisite to attend the course are basic notions of computational mechanics.
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COURSE - Modeling of Offshore Structures
March 16 and 17, 2022 - 10:00am - 1:00pm
In the course, elements for modelling offshore structures will be given. The course is divided into three parts. First, an introduction about structural modelling in offshore environment is discussed in particular how to model simple structures and wave loads. Second, structural dynamics is reviewed and structural modelling with deterministic and statistical loads is considered as well as for linear and nonlinear problems. Third, finite element models and numerical MATLAB codes are discussed for modelling offshore structures. Numerical applications are discussed by taking into account design practices and regulations.
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COURSE - Hands on Continuum Mechanics with COMSOL
March 1-3-8-10, 2022 - 3:00pm - 6:00pm
The goal of this course is to understand the fundamentals of continuum mechanics through worked examples. Participants will tackle some typical problems of continuum mechanics, and will learn to implement a given problem using the weak formulation into the COMSOL software and to discuss the solution.
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COURSE - Relazioni costitutive: modelli molecolari, modelli continui e teorie assiomatiche
February 21-23, 2022 - 3:00pm-5:00pm
Le lezioni saranno dedicate a una esposizione sommaria dei primi sviluppi delle teorie costitutive che, come è noto, si identificano con la nascita della teoria matematica (lineare) dell’elasticità. Si esamineranno i contributi di A. L. Cauchy considerando sia l’approccio ‘molecolare’ che quello continuo. Di entrambi si seguiranno gli sviluppi teorici che conducono alla individuazione delle costanti elastiche e alla determinazione del loro numero in ragione di ipotesi di simmetria materiale. Si giungerà infine, nel caso di isotropia, a mettere in evidenza i risultati che vanno sotto il nome di teoria raricostanti e multicostanti. All’approccio diretto di A. L. Cauchy seguirà quello variazionale di G. Green che, cambiando radicalmente punto di vista, muove dalla definizione di una funzione di energia di deformazione elastica. Entrambi i metodi possono considerarsi il nucleo di teorie assiomatiche e se ne discuteranno le caratteristiche, anche alla luce dei moderni sviluppi delle teorie costitutive. Il tratto caratteristico delle lezioni è costituito da una esposizione che consisterà, essenzialmente, nella lettura di brani di lavori originali sia di A. L. Cauchy che di G. Green. Questa scelta, pur se inusuale, consentirà di mettere in evidenza il processo faticoso, e talvolta tortuoso, degli sviluppi teorici che siamo abituati a esporre e leggere, per evidenti motivi di sintesi e utilità, solo nella loro forma più consolidata e condivisa dalla comunità scientifica. Sia chiaro, però, che queste lezioni non vogliono mettere in discussione l’utilità e la necessità dell’approccio sintetico ma piuttosto, proponendo un pur breve cenno allo sviluppo storico di una teoria, fornire un esempio utile a riflettere sull’evoluzione dei processi scientifici.
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COURSE - Finite Element Method
February 14-16-17-18, 2022 - 11am-2pm
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. As the most commonly used numerical codes rely on the classical displacement-based formulation, this is illustrated in detail. Also, two- and three-field mixed FE approaches are briefly introduced. The main FE families adopted to solve 1D, 2D and 3D continuum problems are dealt with, that is truss, frame, solid, plate and shell FEs are described. Some hints concerning numerical pathological issues and solution strategies are finally given.
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COURSE - Information literacy skills, research strategies and sharing your findings
February 2-3-4-7, 2022 – 10:30am-1:00pm
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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