La ricerca si propone di analizzare una di quelle stagioni architettoniche controverse e lontane dalle internazionali strade maestre del nascente Neues Bauen: il romanticismo-nazionale svedese riletto attraverso l’esperienza del suo massimo esponente, Ragnar Östberg (1866-1945). L’obiettivo della tesi non è solamente quello di una revisione della critica storiografica, facendo così luce su una di quelle personalità considerate marginali, quanto quello di ricavare dalla lettura comparata di due tra i suoi progetti, fino ad ora mai indagati, quegli elementi che fanno dell’architettura un “fatto urbano” in cui la collettività può riconoscersi e parallelamente un fatto di rappresentazione della stessa. L’arcipelago di Stoccolma e quel processo di “renovatio urbis” a cui fu sottoposta proprio agli albori del XX secolo furono gli scenari in cui presero vita i due progetti: il complesso formato dallo Stockholms Stadshuset e la vicina parte mai realizzata del Nämndhuset, e villa Geber. Condensano due dimensioni che la città immersa nel paesaggio contiene: la natura urbana dell’edificio municipale e quella domestica della villa urbana isolata. La ricerca intesse un itinerario di disvelamento attraverso una matrice duale di lettura: “genius loci” e memorie urbane. I capitoli cercano di dimostrare come i due casi-studio siano espressione di quella pendolarità di ricerca tra lo spirito del luogo e le rimembranze delle forme urbane della tradizione. Questa analisi ci conduce in un viaggio alla ricerca dell’atlante delle “memorie urbane”, raccolte nei viaggi e nella formazione, comprendendo così il mondo analogico di riferimenti culturali con altre architetture europee della tradizione. I due progetti sorgono in opposte aree di espansione di Stoccolma e, pur nella loro diversità di scala, sono chiara espressione di appropriatezza al luogo e di strutture formali analoghe. Stockholm Stadshuset-Nämndhuset e villa Geber esprimono il metodo di Östberg, dove i riferimenti raccolti dall’imagination passive sono tramutati ed assemblati grazie alla imagination active. / The research aims to investigate one of the controversial chapters in architecture, far from the linear evolution of the internationally nascent Neues Bauen, that is Swedish National Romanticism through the experience of the leading exponent, Ragnar Östberg (1866-1945). This study is not simply a revision to the overseas reception of the movement, but rather from a comparative analysis between two case-studies to deduce those elements that make architecture an urban fact in which the community can identify. The archipelago of Stockholm and its process of renovatio urbis at the turn of the twentieth century were the backdrop for two projects. These embrace two dimensions of living: the urban framework of the municipal centre and the domestic framework of the partially isolated villa. Therefore, the purpose of the research is to embark on a voyage of discovery approaching two instances of Östberg’s artwork through a twofold critical interpretation: genius loci and urban memories. The chapters attempt to demonstrate how the two projects inevitably oscillate between seeking the spirit of the place and harking back to urban forms of tradition. The investigation leads us to penetrate Östberg’s repertoire of urban memories, as amassed from travel and study, and trace analogies of composition with other architecture in the European tradition. The two case-studies are placed on opposite sides of developing Stockholm: the first on the outermost portion of the Kungsholmen peninsula and the second along the banks of the Djurgård canal. Although they are clearly different-scale projects, they also reveal a similar approach to composition. The Stockholm City Hall, including its nearby never-to-be realized part, the Commission Building, and villa Geber can be seen as significant examples of Östberg’s design process: how from the imagination passive studies and select references to imagination active he manages to assemble and combine his inputs.

La presente Tesi di Dottorato intende affrontare una lettura critica della Casa in Belvederestraße 60, realizzata dall’architetto Oswald Mathias Ungers (Kaisersesch, 12 luglio 1926 – Köln, 30 settembre 2007), nel 1958-’59 a Köln-Müngersdorf, come studio per sé ed abitazione per la propria famiglia. Questo primo oggetto della ricerca viene considerato evidente espressione delle convinzioni formali e compositive dell’architetto, negli anni Cinquanta e Sessanta. A differenza di altri progetti residenziali coevi ed antecedenti, frutto di un’elaborazione autonoma, la prima casa che costruisce per sé riflette una maggiore libertà di pensiero, dettata dalla coincidenza delle figure di progettista e committente; a ciò si aggiunge anche una precisa volontà dichiarativa ed ideologica. Proprio quest’ultimo aspetto permette di introdurre il secondo oggetto della Tesi: il manifesto “ideologico”, Zu einer neuen Architektur, scritto dallo stesso Oswald Mathias Ungers e da Reinhard Gieselmann, alla fine del 1960; un breve testo che espone, con toni perentori ed inappellabili, il punto di vista dei due architetti nei confronti di un panorama architettonico e critico, caratterizzato da una sterilità di pensiero dilagante, a causa dell’egemonia costruttiva funzionalista. La ricerca indaga quindi le forti reciprocità delle due opere: casa e testo, viste in chiave di “manifesto scritto e manifesto costruito”. Il primo legame tra i due soggetti è senza dubbio la concomitanza temporale, (tra il 1958 ed il 1960) associata ad un rapporto causa-effetto, tale per cui il manifesto viene redatto a difesa delle aspre critiche scaturite dalla pubblicazione della casa sulla rivista Bauwelt. Il secondo nesso è la possibilità di comprendere le accezioni effettive dei termini impiegati nella redazione del testo, attraverso le forme di una delle opere maggiormente personali dell’architetto, estraendone il senso e conferendogli un’immagine architettonica. Si vuole creare così un rapporto biunivoco di traducibilità, dell’architettura nello scritto e della semantica ungersiana in azioni compositive. / This PhD Thesis aims to treat a critical reading of the House at 60 Belvederestraße, designed by Oswald Mathias Ungers (Kaisersesch, 1926 – Cologne, 2007) in 1958-1959 in Cologne-Müngersdorf, as a studio for himself and a dwelling for his family. This first objective of this research is considered obvious expression of the architect’s formal and compositional beliefs, in the Fifties and Sixties. Unlike other previous and contemporary residential projects, result of a stand-alone processing, the first house that he builds for himself reflects a greater freedom of thought, mostly due to the fact that the designer and the client were the same person; in addition, there is also a clear declarative and ideological desire behind it. This last aspect allows the introduction of the second objective of the Thesis: the “ideological” manifesto, Zu einer neuen Architektur, written by Ungers and Reinhard Gieselmann, at the end of 1960: a short text that exposes, the views of the two architects against an architectural and critic outline, characterized by a widespread sterility of thought, due to the hegemony of the constructive functionalism. The research investigates the strong reciprocity of two works: house and text, seen as “manifesto-written” and “manifesto-built”. The first link between the subjects is undoubtedly the combination of time associated with a cause-effect relationship, such that the manifesto is realized to defend the harsh criticism arising from the publication of the home into the review Bauwelt. The second link is the possibility to understand the actual meanings of the words used in the text, through the forms of one of the most personal works of the architect, extracting the meaning and giving it an architectural image. The study wants to create a two-way relationship of translatability, from architecture into writing and from Ungers’ semantics into compositional actions.

Environmental decay in porous masonry materials, such as brick and mortar, is a widespread problem concerning both new and historic masonry structures. The decay mechanisms are quite complex dependng upon several interconnected parameters and from the interaction with the specific micro-climate. Materials undergo aesthetical and substantial changes in character but while many studies have been carried out, the mechanical aspect has been largely understudied while it bears true importance from the structural viewpoint. A quantitative assessment of the masonry material degradation and how it affects the load-bearing capacity of masonry structures appears missing. The research work carried out, limiting the attention to brick masonry addresses this issue through an experimental laboratory approach via different integrated testing procedures, both non-destructive and mechanical, together with monitoring methods. Attention was focused on transport of moisture and salts and on the damaging effects caused by the crystallization of two different salts, sodium chloride and sodium sulphate. Many series of masonry specimens, very different in size and purposes were used to track the damage process since its beginning and to monitor its evolution over a number of years Athe same time suitable testing techniques, non-destructive, mini-invasive, analytical, of monitoring, were validated for these purposes. The specimens were exposed to different aggressive agents (in terms of type of salt, of brine concentration, of artificial vs. open-air natural ageing, …), tested by different means (qualitative vs. quantitative, non destructive vs. mechanical testing, punctual vs. wide areas, …), and had different size (1-, 2-, 3-header thick walls, full-scale walls vs. small size specimens, brick columns and triplets vs. small walls, masonry specimens vs. single units of brick and mortar prisms, …). Different advanced testing methods and novel monitoring techniques were applied in an integrated holistic approach, for quantitative assessment of masonry health state.

How to evaluate the cost-effectiveness of repair/retrofit intervention vs. demolition/replacement and what level of shaking intensity can the chosen repairing/retrofit technique sustain are open questions affecting either the pre-earthquake prevention, the post-earthquake emergency and the reconstruction phases. The (mis)conception that the cost of retrofit interventions would increase linearly with the achieved seismic performance (%NBS) often discourages stakeholders to consider repair/retrofit options in a post-earthquake damage situation. Similarly, in a pre-earthquake phase, the minimum (by-law) level of %NBS might be targeted, leading in some cases to no-action. Furthermore, the performance measure enforcing owners to take action, the %NBS, is generally evaluated deterministically. Not directly reflecting epistemic and aleatory uncertainties, the assessment can result in misleading confidence on the expected performance. The present study aims at contributing to the delicate decision-making process of repair/retrofit vs. demolition/replacement, by developing a framework to assist stakeholders with the evaluation of the effects in terms of long-term losses and benefits of an increment in their initial investment (targeted retrofit level) and highlighting the uncertainties hidden behind a deterministic approach. For a pre-1970 case study building, different retrofit solutions are considered, targeting different levels of %NBS, and the actual probability of reaching Collapse when considering a suite of ground-motions is evaluated, providing a correlation between %NBS and Risk. Both a simplified and a probabilistic loss modelling are then undertaken to study the relationship between %NBS and expected direct and indirect losses.

No description available.

In this work, the Generalized Beam Theory (GBT) is used as the main tool to analyze the mechanics of thin-walled beams. After an introduction to the subject and a quick review of some of the most well-known approaches to describe the behaviour of thin-walled beams, a novel formulation of the GBT is presented. This formulation contains the classic shear-deformable GBT available in the literature and contributes an additional description of cross-section warping that is variable along the wall thickness besides along the wall midline. Shear deformation is introduced in such a way that the classical shear strain components of the Timoshenko beam theory are recovered exactly. According to the new kinematics proposed, a reviewed form of the cross-section analysis procedure is devised, based on a unique modal decomposition. Later, a procedure for a posteriori reconstruction of all the three-dimensional stress components in the finite element analysis of thin-walled beams using the GBT is presented. The reconstruction is simple and based on the use of three-dimensional equilibrium equations and of the RCP procedure. Finally, once the stress reconstruction procedure is presented, a study of several existing issues on the constitutive relations in the GBT is carried out. Specifically, a constitutive law based on mirroring the kinematic constraints of the GBT model into a specific stress field assumption is proposed. It is shown that this method is equally valid for isotropic and orthotropic beams and coincides with the conventional GBT approach available in the literature. Later on, an analogous procedure is presented for the case of laminated beams. Lastly, as a way to improve an inherently poor description of shear deformability in the GBT, the introduction of shear correction factors is proposed. Throughout this work, numerous examples are provided to determine the validity of all the proposed contributions to the field.

This thesis focuses on minor-destructive testing (MDT) techniques for the mechanical characterisation of historical mortars, as it is a fundamental task for the assessment of existing masonries. In the first part, a novel in-situ MDT technique is investigated, based on the field vane shear test for soils. The instrumentation consists in a four-winged pin (X-Drill) and a torque wrench. This research presents the results of an experimental campaign based on the comparison between standard tests and X-Drill measurements on different types of mortars. The interpretation of the test provides a possible correlation between the measured torque and the compressive strength of the material. In the second part, the thesis focuses on the extraction of samples to be tested in the laboratory. Brazilian tests can be carried out on cores including a diametral mortar joint with a defined inclination with respect to its original horizontal position. A new integrated methodology is developed for the comprehensive mechanical characterization of historical mortar based on different types of experimental tests results. This task is carried out by means of a large set of experiments performed ex-novo on lime mortar masonry walls built in the laboratory. The processing of the results from Brazilian tests on cores with inclined diametral joint is complemented with the application of the double punch tests on mortar joints that may be also extracted through core drilling. The proposed experimental methodology is then compared with the results obtained from standard tests performed on the same materials, such as compression tests, flexural tests and shear tests on triplets. Finally, the parameters obtained are used as input parameters for 2D and 3D numerical analyses based on the Continuum Damage Mechanics constitutive model. The comparison between the experimental results and the numerical analyses confirms the good prediction capacity of the proposed techniques.

In this work, the Generalized Beam Theory (GBT) is used as the main tool to analyze the mechanics of thin-walled beams. After a brief introduction to the subject, the attention is focused on the constitutive relations both for the isotropic and the orthotropic cases. In particular, a novel approach based on energetic arguments , able to automatically select appropriate constitutive relations in accordance with the GBT kinematics, is presented. Furthermore, the concept of consistency of a GBT-based model is introduced and a consistency analysis is conducted. This provides a formal basis to investigate the effects of various families of cross-section deformation modes in terms of predictive capabilities of the GBT model. Later, a new finite element for GBT beams is presented. The element is based on the hybrid complementary energy functional, involving nodal displacements and equilibrating stresses within the element as indipendent variables. Assumed stresses are rationally derived basing on the stresses associated to analytical solutions of some particular cases. The numerical results show the high performance of the proposed element. Subsequently, in the framework of cold-formed stability verification, a verification approach called Embedded Stability Analysis is shown. The verification approach, based on the GBT, is an interesting alternative to the simplified procedures provided by current standards and it is applicable in a simple and general way. A synthetic parameter allows the designer to evaluate when it is more appropriate to consider the distortional effects in thin-walled stability check. Finally, in the framework of cold-formed stability analysis, a new version of the so-called approach ECBL (Erosion of the Critical Load Bifurcation), based on the GBT, is presented. The numerical results show an excellent agreement between the new version ECBL approach and the experimental results.

L’obiettivo della ricerca è stato quello di sviluppare un metodo di calcolo semplificato per l’analisi non lineare di strutture in muratura soggette ad azione sismica, attraverso l’implementazione di un codice caratterizzato da un’elevata versatilità e semplicità di utilizzo, in grado di conseguire un bilanciato compromesso tra validità teorico-sperimentale e praticità applicativa. Il codice, sviluppato in ambiente Microsoft Excel tramite il linguaggio di programmazione Microsoft Visual Basic 6.3, punta a guidare il progettista, attraverso un’interfaccia semplice ed intuitiva, nel delicato compito di svolgere un’analisi non lineare di pareti murarie caricate nel proprio piano, fornendo, in corrispondenza di ogni singolo step di carico, una rappresentazione puntuale e intuitiva degli elementi costituenti la parete, individuandone immediatamente le possibili criticità. Attraverso un’interfaccia user-friendly l’utente ha la possibilità di inserire le caratteristiche geometriche e meccaniche della parete, giungendo agevolmente alla definizione del modello a telaio equivalente e alla definizione della curva di capacità della struttura. Attraverso il calcolo della domanda sismica e la valutazione del punto di funzionamento, il codice indirizza l’utente all’individuazione mirata degli interventi di miglioramento necessari, a seconda che si voglia diminuire la domanda o aumentare la capacità di spostamento della parete. Essendo il sottoscritto un Ufficiale del Corpo degli Ingegneri dell’Esercito Italiano, un codice di questo tipo si presterebbe ad essere utilizzato dall’Amministrazione Difesa nell’ambito delle verifiche di vulnerabilità sismica degli edifici strategici: con tale applicativo, infatti, i Reparti del Genio Militare potrebbero effettuare una prima verifica (caratterizzata da un accettabile compromesso tra la speditezza e l’accuratezza dei risultati forniti) di tali strutture, individuando le maggiori criticità relative agli immobili del demanio militare e progettando, ove necessario, i conseguenti interventi di consolidamento, per poi programmare in modo maggiormente oculato l’affidamento delle verifiche di vulnerabilità previste dalla normativa attualmente in vigore. / The aim of this thesis work is to develop a simplified method for non linear analysis of masonry structures subjected to seismic action, throughout the implementation of an high versatility and simple-use code, in order to have a balanced compromise between theoretical and experimental efficiency and practical applicability. The code, written for Microsoft Excel using Microsoft Visual Basic 6.3 programming language, aims for guiding the structural designer, through a simple and intuitive interface, in the delicate task of a non linear analysis of masonry wall loaded in its own plane, giving, in correspondence of each load step, a punctual and intuitive representation of its elements, instantly defining the critical masonry panels and their failure mode. Thanks to a user-friendly interface, the user can insert geometrical and mechanical features of masonry wall, easily arriving to define the equivalent frame model and the capacity curve. Through the calculus of the seismic request and the evaluation of performance point, the code guides the user to the focused identification of proper improvement interventions, either decreasing seismic demand or increasing seismic capacity. Since I am an Officer of Italian Army Corps of Engineers, a code like the one developed could be efficiently used by military engineers for seismic vulnerability verifications of so called strategic buildings: with this application, each military unit could carry out a first approach (characterized by an acceptable compromise between rapidity and accuracy of the supplied results) for that kind of structures, identifying the main critical issues related to military buildings and designing, if necessary, the adequate improvement interventions, in order to carefully program the externalization of seismic vulnerability analysis services provided for by actual law.

The 2012 Emilia earthquakes caused significant damages to existing precast RC structures. These buildings were found being extremely vulnerable because, being designed for vertical loads only, they featured friction-based connections between structural elements, and in particular between beams and columns. Given the large diffusion of these structures as industrial buildings, and consequently the high social and economic impact of damages, their retrofit is critical. Various techniques have been proposed in the literature; in most of them friction-based connections are removed by inserting mechanical connectors that will make beam-column connections hinged. These approaches lead to a significant increase of the base shear and therefore often require strengthening of columns and foundations. The research presents dissipative devices based on carbon-wrapped steel tubes to be used as an alternative low-damage solution for the retrofit of beam-column friction connections able to minimize structural damages. Firstly, the study presents results of experimental tests on the devices and discusses their innovative energy absorption mechanism and dissipative behaviour. Then, numerical analyses carried on to investigate the effectiveness of the introduction of dissipative devices in beam-column connections of precast structures are presented. Incremental Dynamic Analyses have been performed in order to evaluate an equivalent behaviour factor for structures with dissipative devices, by comparing the seismic response of simple frame structures with dissipative connections with equivalent elastic systems. Findings of numerical investigation show how the introduction of the dissipative devices in friction-based joints provides an effective connection between structural elements and, in addition, the capability to reduce forces transmitted to the columns, improving the seismic behaviour of the entire structure. Finally, a simplified approach to evaluate an equivalent behaviour factor for a structure equipped with dissipative devices in friction-based beam-column joints is proposed.