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The development of renewable energies and the desired independence from fossil energy sources are essential for security of supply. Wind energy turbines already account for the largest share of electricity generation in Germany. As part of modular precast concepts for wind turbine towers, vertical joints now divide the segments into even smaller components. This significantly reduces transport costs and installation time. The load-bearing behaviour of these segmented concrete towers is very complex due to the horizontal and vertical joints and the resulting restrained cross-sectional deformations. In the case of thin-walled half-shell segments now used in modern wind turbine towers, cross-sectional distortion and warping can significantly reduce the load-bearing capacity. Even under pure torsional loading, there is a decrease in the horizontal joint load capacity compared to conventional thin-walled circular rings. However, there are currently no design approaches for this new construction, as the structural behaviour is neither fully understood nor reliably modeled. This cumulative dissertation deals with the modeling of the torsional behaviour of segmented concrete towers for wind turbines based on the warping theory of thin-walled bars. Transferring the complex mechanical relationships into an understandable and comprehensible bar model allows differentiated evaluation approaches. In the case of segmented concrete towers, this leads to the long-term realization of even more innovative, higher and safer tower concepts. With this calculation approach, the practical engineer always remains in control of his or her own actions. Accordingly, the results can be used as a basis for evaluation without much need for interpretation, e.g. to assess the effect of restrained sectional warping on the distribution of normal stresses. The successive derivation of an engineering approach is presented using mechanical modeling concepts and non-linear numerical investigations as we, Der Ausbau der erneuerbaren Energien und die angestrebte Unabhängigkeit von fossilen Energieträgern sind für die Versorgungssicherheit unerlässlich. Den größten Anteil an der Stromerzeugung haben in Deutschland schon heute die Windenergieanlagen. Im Rahmen modularer Fertigteilkonzepte für Türme von Windenergieanlagen teilen mittlerweile Vertikalfugen die Segmente in immer kleinere Komponenten. Auf diese Weise können die Transportkosten und der Montageaufwand erheblich reduziert werden. Das Tragverhalten dieser segmentierten Betontürme ist aufgrund der horizontalen und vertikalen Fugen sowie der daraus resultierenden behinderten Querschnittsverformungen sehr komplex. Bei dünnwandigen Halbschalensegmenten, die inzwischen im modernen Turmbau für Windenergieanlagen eingesetzt werden, können Querschnittsverzerrungen und -verwölbungen die Tragfähigkeit erheblich beeinträchtigen. Bereits bei einer reinen Torsionsbelastung ist im Vergleich zu konventionellen dünnwandigen Kreisringen eine Abnahme der horizontalen Fugentragfähigkeit zu erkennen. Es existieren zurzeit jedoch noch keine Bemessungsansätze für die neuartige Konstruktion, da weder das Strukturverhalten vollständig verstanden ist, noch verlässlich modelliert werden kann. Diese kumulative Dissertation befasst sich daher mit der Modellierung des Torsionstragverhaltens von segmentierten Betontürmen für Windenergieanlagen auf Basis der Wölbtheorie dünnwandiger Stäbe. Ziel ist die realitätsnahe Abbildung des Torsionstragverhaltens der hybriden Turmkonstruktion durch die sukzessive Entwicklung eines Ingenieurmodells. Die Übertragung der komplexen mechanischen Zusammenhänge in ein verständliches Stabmodell ermöglicht differenzierte Bewertungsansätze. Dies führt im Anwendungsfall der segmentierten Betontürme langfristig zur Realisierung noch innovativerer, höherer und sicherer Turmkonzepte. Mit diesem Berechnungsansatz behalten die in der Praxis tätigen Ingenieur:innen stets die Kontroll

Within the frame of the revision of the Eurocode 2 for concrete structures, the section devoted to strut-and-tie design has been updated to enhance its applicability, its consistency with other sections and its ease-of-use. As a result, a number of changes have been introduced. Namely, the use of stress fields and their combination with classical strut-and-tie models has been incorporated. The changes in this section can be seen as an effort to provide a more comprehensive and general tool for designers, that can be transparently applied to any structural member with sufficient reinforcement for crack control. In this paper, the consistency between the strut-and-tie and the stress field methods is clarified as well as the fundamentals of the revision performed in Eurocode 2. The paper also elaborates how the code can be used for advanced analyses, considering in an explicit manner the compatibility of deformations to obtain refined estimates of the structural resistance..

Assessing a structure’s intrinsic level of robustness is a widespread problem in the field of structural engineering and has taken on even greater importance since the attacks of September 11, 2001. Although numerous robustness approaches can be found in the literature, there is still today no consensus on which threshold makes a given structure robust or not, nor on the way to calculate this threshold. Moreover, all the existing methods are based on a numerical assessment of the structure’s aptitude for robustness once its design has been fixed. This thesis is about the development of a new type of approach to structural robustness, working on geometrical considerations only. It allows the integration of some constitutive dimensions of structural robustness – such as the aptitude for force redistributions – at the earliest steps of the design process. Based on graphic statics and strut-and-tie modelling, the method develops a visual robustness indicator showing structural aptitude for force redistributions. When implemented into parametrical software such as Rhino and its graphic algorithm editor Grasshopper, the approach also turns into an interactive tool. This interactivity may help project authors to understand the impact of design decisions on the robustness performance sought for (in terms of aptitude for force redistributions). Combined with Maxwell’s theorem of load paths, the method also allows the comparison of the efficiency of various design options in terms of the volume of material required for their implementation. The principles of the proposed geometrical method are developed in this thesis for two-dimensional structures. These principles are then illustrated by the analysis of four case studies. Two concern arched structures, the first in pure compression, the second in compression and bending. Two sets of walls are then studied, the first made of an ideal material with identical compressive and tensile strengths, the second intended to prepare th, (FSA - Sciences de l'ingénieur) -- UCL, 2019

This thesis introduces “constraint-based graphic statics”, a geometrical support for computer-aided structural design. This support increases the freedom with which the designer interacts with the plane static equilibriums being shaped. Constraint-based graphic statics takes full advantage of geometry, both its visual expressiveness and its capacity to solve complex problems in simple terms. Accordingly, the approach builds on the two diagrams of classical graphic statics: a form diagram describing the geometry of a strut-and-tie network and a force diagram vectorially representing its inner static equilibrium. Two new devices improve the control of these diagrams: (1) nodes — considered as the only variables — are constrained within Boolean combinations of graphical regions; and (2) the user modifies these diagrams by means of successive operations whose geometric properties do not at any time jeopardise the static equilibrium of the strut-and-tie network. These two devices offer useful features, such as the ability to describe, constrain and modify any static equilibrium using purely geometric grammar, the ability to compute and handle multiple solutions to a problem at the same time, the ability to switch the hierarchy of constraint dependencies, the ability to execute dynamic conditional statements graphically, the ability to compute full interdependency and therefore the ability to remove significantly the limitations of compass-and-straightedge constructions and, finally the ability to propagate some solution domains symbolically. As a result, constraint-based graphic statics encourages the emergence of new structural design approaches that are highly interactive, precognitive and chronology-free: highly interactive because forces and geometries are simultaneously and dynamically steered by the designer; precognitive because the graphical region constraining each points marks out the set of available solutions before they are even explored by the user; and chr, (FSA - Sciences de l'ingénieur) -- UCL, 2013

The shear resistance of elements without stirrups has mainly been investigated by test setups involving simply supported beams of constant thickness subjected to one- or two-point loading, and most of the formulas included in codes have been adjusted using this experimental background. It is a fact, however, that most design situations involve constant or triangular distributed loading (such as retaining walls or footings) on tapered members. Furthermore, there seems to be few shear tests involving cantilever structures subjected to distributed loading. These structures, which are common in everyday practice, fail in shear near the clamped end, where the shear forces and bending moments are maximum (contrary to simply supported beams of tests, where shear failures under distributed loading develop near the support region for large shear forces but limited bending moments). In this paper, a specific testing program undertaken at the Poly- technic University of Madrid (UPM), Madrid, Spain, in close collab- oration with Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland, is presented. It was aimed at investigating the influence of load distribution and tapered beam geometrics on the shear strength. The experimental program consists of eight slender beams without stirrups. Four specimens had a constant depth, whereas the others had variable depths (maximum depth of 600 mm [23.6 in.]). Each specimen was tested twice: one side was tested first under point loading, and then (after repairing) the other side was tested under either uniform loading or triangular loading. The setup allowed direct comparisons between point and distributed loading. The experimental results showed a significant influence of the type of loading and of tapered geometries on the shear strength. On the basis of these results, and using the funda- mentals of the critical shear crack theory, a consistent physical explanation of the observed failure modes and differences in shear str

En las losas soportadas por apoyos puntuales y en aquellas que están sometidas a importantes cargas concentradas, así como en zapatas y en otras estructuras superficiales, es necesario verificar la resistencia frente a esfuerzo cortante alrededor del soporte o de las cargas concentradas, ya que frecuentemente ésta es la condición que determina el espesor de la losa o la zapata y también las dimensiones de los soportes o los capiteles. Este fenómeno se conoce como punzonamiento. La rotura por punzonamiento en losas sin armadura de cortante se produce de manera frágil, por lo cual es particularmente indeseable y conviene prestarle gran atención tanto en la concepción como en la ejecución. De manera frecuente, la presencia de pilares de borde y esquina es elevada y su proporción respecto a las columnas interiores es grande. Es por ello que resulta necesaria una buena comprensión del fenómeno del punzonamiento en este tipo de estructuras. El punzonamiento en losas es uno de los problemas más estudiados en las estructuras de hormigón, pese a ello, resulta ser todavía parcialmente desconocido y carece de una unificación en su tratamiento. El dimensionamiento basado en la verificación de un esfuerzo cortante nominal (medido sobre un perímetro llamado crítico) comparado con una resistencia obtenida por métodos empíricos, se impone en casi todas las normativas debido a su simplicidad. Los ensayos muestran que otros parámetros como la cuantía de armadura, el tamaño de árido o el efecto escala tienen también influencia sobre la resistencia nominal. Los objetivos de esta tesina son contribuir a la comprensión del punzonamiento en losas de hormigón armado sin armadura de punzonamiento sobre pilares de borde y esquina, comparar la predicción de las diferentes normas respecto a diversas series de ensayos recogidas en la literatura y verificar el buen comportamiento de la teoría de la fisura crítica. El cálculo de la resistencia al punzonamiento según la teoría de la fisura crítica

El present treball és un anàlisi i diagnòstic de l'estructura mòbil de la Villa Girasole, edifici singular en formigó armat que fou construït en 1935 per l'enginyer civil Angelo Invernizzi a Marcellise, Verona. La principal característica d'aquest edifici resideix en la seva mobilitat: en efecte, sobre una part fixa, l'estructura principal és capaç; de girar 360 graus per orientar-se cap el sol. Una altre característica remarcable és la seva magnitud, amb més de 42 metres d'alçada i 23 d'amplada la part mòbil té un pes de 1500 T. Per tal de donar mobilitat a l'estructura, l'enginyer la construeix sobre rails i la fa girar gràcies a dos rodets motoritzats. Després la mort de l'enginyer en 1958, la Villa Girasole va quedant poc a poc deteriorada i la seva mobilitat reduïda. Actualment, gràcies a la col·laboració entre la filla de l'enginyer i l'Accademia di architettura di Mendrisio s'ha creat una fundació amb l'objectiu de recuperar i tornar a fer girar aquesta meravella de l'arquitectura. Mitjançant aquest treball es pretén analitzar l'estructura mòbil i determinar la seva conformitat segons la norma suïssa actual, SIA 2003. La motivació ve donada degut a una primera inspecció que determina en bon estat els mecanismes de rotació però assenyala problemes de cimentació com els responsables de l'aturada de la part mòbil de l'estructura. L'estudi comença amb un resum històric de la bibliografia dels autors del projecte per situar-nos dins del context. Seguidament, es compara la Villa Girasole amb la resta d'edificis giratoris existents per veure'n l'evolució i el futur d'aquestes. A continuació, el treball es centra únicament en l’anàlisi estructural de la part mòbil de la Villa Girasole. Gràcies a la recopilació de la informació existent de l'edifici i a la visita del mateix es crea un model estàtic global de l'estructura. EI primer anàlisi realitzat és a l'Estat Límit Últim utilitzant diferents models reduïts per determinar les sol·licitacions. La seguretat a flexió c

El presente proyecto tiene por objetivo crear un nuevo viaducto inscrito en las obras de la nueva autopista ( Transjurane ) de categoría 2 que unirá en el 2016 Francia (Delle) y la llanura Suiza (Bienne). El viaducto constituye una de las obras más destacadas del sector 2 entre Boncourt y Porrentruy Ouest de 13,5 kilómetros de longitud.