CORSO - Recenti sviluppi nella progettazione di opere in sotterraneo
5, 6, 7,12,13,14,15,16, 20 dicembre 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
CORSO - An introduction to the mechanics of soils
22 novembre 2022, 09:30-11:30, 12:30-13:30, 14:30-16:00; 23-24 novembre 2022, 10:00-12:30, 14:00-16:00
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.
CORSO - Seismic Safety and Sustainability:Next Generation of Low-Damage Concrete and Timber Buildings
15-17-18 novembre 2022 - 10:00-13:00
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.
CORSO - Introduction to Nano-mechanics: Continuum Modeling and Atomistic Simulation
9-10-11 novembre 2022 - 10:00-13:00
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.
CORSO - Soft Mechanics and Instabilities
25, 26, 27 e 28 ottobre 2022 - 12:00-13:00, 14:00-16:00
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.
SEMINARIO - Thrust Network Analysis of Masonry Vaults
14 ottobre 2022 - ore 16:00-16:45
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.
SEMINARIO - Recent Advancements in the Modeling of Hysteretic Phenomena for Mechanical Systems and Materials
14 ottobre 2022 - ore 17:15-18:00
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.
SEMINARIO - Out-of-plane instability of ductile reinforced concrete structural walls: Failure mechanism and key design recommendations
26 settembre 2022 dalle 17:00 alle 18:00
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.
CORSO - Pile foundations under seismic loading
18, 20 e 21 luglio 2022 - 14:30-17:30, 10:00-13:00, 11:00-13:00
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.
CORSO - Ultrasonic wave propagation in classical and non-classical continua. Applications to material characterization, damage imaging and stress monitoring
12-14-15 luglio 2022 - 15:00-17:00
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.