Historical review of lighthouse design under wind load: the Ile Vierge lighthouse

International audienceThe purpose of the study presented here is to describe the design method used by engineers in the 19 th and early 20 th centuries to size lighthouses structures, and to compare them with current European standards. The historical information presented here is derived from two sources in particular: the archives of the Ile Vierge lighthouse, which was built at the northern tip of Brittany between 1897 and 1902, and the scientific journals, books and courses available at that time. Firstly, the article describes the structure of the Ile Vierge lighthouse which is the tallest stone lighthouse in Europe. The wind load acting on lighthouses and chimneys was formulated in France by L. Fresnel in 1825. Fresnel's work is compared to WJ M. Rankine's theory used in the UK. The safety coefficients applied with respect to the stability of the towers in France and the UK in the 19 th century are compared. On the occasion of the construction of the Ile Vierge lighthouse, the masonry strength under wind loads led to discussion among engineers of the French lighthouse authorities. They also worried about the risk of excessive oscillations of the towers, which could cause a dysfunction of the lamp. Thirdly, the standard wind action defined in Eurocode 1 is applied to the Ile Vierge lighthouse. Calculation results are given. A comparative analysis of the ancient and modern methods is presented. Overall, this historical research shows that the designers of lighthouses in the 19 th century had the same objectives as today: to build strong, durable structures in which deformations under loads are compatible with serviceability

La mécanisation de la briqueterie toulousaine Gélis (1924- 1990) d'après la description et le dessin de ses machines

International audienc

Les ponts en maçonnerie du 19è siècle Le cas d'ouvrages ferroviaires du Midi Toulousain

International audienceThe aim of research presented here is to achieve a better understanding of the technology of masonry arch bridges. The study is a historical research. It relates eleven bridges of a railway line built in 1870 in Toulouse region (South West of France). The materials and the processes used for the construction are identified. A typology of bridges is determined. It is compared with the techniques commonly used in the late 19th century, described in technical books written between 1880 and 1924. Finally, some suggestions are made in order to assess masonry arch bridges.Le but de la recherche présentée ici est de parvenir à une meilleure connaissance de la technologie des ponts en maçonnerie. L'étude, de nature historique, concerne onze ouvrages d'une ligne ferroviaire construits en 1870 en région toulousaine. Elle a permis d'identifier avec exactitude les matériaux mis en oeuvre et les procédés constructifs utilisés. Une typologie est dégagée. Elle est comparée avec les techniques couramment utilisées à la fin du 19 ème siècle et relatées dans les livres techniques contemporains de la construction. Finalement, des pistes de réflexion sont proposées concernant la conservation et la requalification des ponts en maçonnerie

La mécanisation de la briqueterie toulousaine Gélis (1924- 1990) d'après la description et le dessin de ses machines

International audienc

Les ponts en maçonnerie du 19è siècle Le cas d'ouvrages ferroviaires du Midi Toulousain

International audienceThe aim of research presented here is to achieve a better understanding of the technology of masonry arch bridges. The study is a historical research. It relates eleven bridges of a railway line built in 1870 in Toulouse region (South West of France). The materials and the processes used for the construction are identified. A typology of bridges is determined. It is compared with the techniques commonly used in the late 19th century, described in technical books written between 1880 and 1924. Finally, some suggestions are made in order to assess masonry arch bridges.Le but de la recherche présentée ici est de parvenir à une meilleure connaissance de la technologie des ponts en maçonnerie. L'étude, de nature historique, concerne onze ouvrages d'une ligne ferroviaire construits en 1870 en région toulousaine. Elle a permis d'identifier avec exactitude les matériaux mis en oeuvre et les procédés constructifs utilisés. Une typologie est dégagée. Elle est comparée avec les techniques couramment utilisées à la fin du 19 ème siècle et relatées dans les livres techniques contemporains de la construction. Finalement, des pistes de réflexion sont proposées concernant la conservation et la requalification des ponts en maçonnerie

Méthode de requalification des ponts en maçonnerie

ABSTRACTIn the French railway system, 43% of all bridges are masonry bridges. For Réseau Ferré de France and all the owners who have to maintain existing structures, the evaluation and renovation of old bridges are necessary in order to allow for a more aesthetically pleasing environment and to make adaptations to new requirements of the traffic easier. The computation and modelling of masonry bridges is one strategy available. It is unusual to compute a vault for lack of efficient realistic tool describing precisely the behaviour under service load. The aim of this thesis is to build a model allowing to analyze and understand how masonry bridges resist.The method is a three step process.It first deals with historical research and has resulted in the accurate description of the bridges built for a railway line by the Compagnie des Chemins de Fer du Midi, in the south west of France, in 1870. They were all designed using the same techniques and materials such as limestone, moulded bricks and hydraulic lime mortar. Secondly, an experimental method to test the materials used to create the structure has been worked out. It has resulted in the creation of models of their mechanistic behaviour, one for each of the three materials composing the masonries and for each of the complete masonry, by non-linear numerical homogenisation method. The interface between blocks and bonds has been modelled too.Thirdly, some calculations on one of the railway bridges by FEM have been run. The mesh is built in 3D. It describes all the parts of the bridge, including the vault, the spandrel walls, the abutments and the filling. The bridge is divided into homogenised macro-elements, tied by interface bonds which break in tension like cracks. Two types of boundaries conditions have been considered in this situation : when displacement is impossible on the ground or when the bridge is elastically supported with permitted sliding. The load applied on the bridges comes from two axles whose intensity increases until collapse. A parametric study has been made to find the factors involved in the bridge security. Finally, future developments have been proposed to enhance our knowledge of old masonry arches. Their aim is to approach the reality and variety of existing bridges.Sur le réseau ferroviaire français, 43% des ouvrages sont en maçonnerie soit environ 18000 ponts. Pour RFF et tous les gestionnaires d’un parc d’ouvrages d’art de ce type, la requalification des ouvrages anciens est donc une nécessité, dans la mesure où elle participe à l’optimisation de l’exploitation des ressources, et facilite l’adaptation à de nouveaux besoins face à un trafic qui évolue sans cesse. Le calcul des ponts en maçonnerie s’inscrit dans cette démarche. Mais il est peu utilisé faute d’outil efficace vis à vis du comportement en service. Cette thèse a pour but de construire un modèle de calcul pour mieux comprendre comment les ponts en maçonnerie résistent. La méthode de recherche est construite en trois étapes.La première étape est une recherche historique. Elle a abouti à la description précise des ponts d’une ancienne ligne de chemin de fer construite dans le département du Tarn vers 1870. Ils sont tous conçus suivant le même principe et avec les mêmes matériaux, parfaitement identifiés : pierre calcaire, brique pleine moulée, mortier de chaux hydraulique. Dans la seconde étape, ces matériaux identifiés ont été testés mécaniquement. A la suite de cette recherche expérimentale, un modèle de comportement mécanique a été proposé, pour chacun d’eux individuellement, puis pour les maçonneries dans leur ensemble, par homogénéisation non linéaire. Un modèle est également proposé pour l’interface entre les joints de mortier et les blocs. La troisième étape est le calcul de l’un des ouvrages de la ligne par la méthode des éléments finis, à l’aide du code CASTEM. Le maillage est construit en trois dimensions. Il inclut toutes les parties de l’ouvrage, culées, murs, voûte, bandeaux, remplissage. L’ouvrage est divisé en voussoirs homogénéisés, liés entre eux par des joints qui peuvent s’ouvrir en traction, comme des fissures, et glisser. Deux types de conditions aux limites sont envisagées : blocage total sur le sol, ou bien appuis élastiques glissants. Le pont est soumis au poids d’un véhicule dont l’intensité est croissante jusqu’à rupture de l’ouvrage. Une étude paramétrique est fournie pour déceler les facteurs influençant la sécurité du pont.Finalement, des développements sont proposés pour améliorer nos connaissances sur les ponts maçonnés. Ils doivent permettre de se rapprocher au mieux de la réalité et de la diversité des ponts existants

La mécanisation de la briqueterie toulousaine Gélis (1924- 1990) d'après la description et le dessin de ses machines

International audienc

Assessment method of masonry arch bridges

International audienceThe aim of the research presented here was to build an assessment method for masonry arch bridges by modelling and computing. The method was developed on a masonry vault build in 1870 in southwest of France with bricks, stones and hydraulic lime. The first step was an historic research in order to know the bridge constitution. The second step was an experimental approach whose aim was to establish the homogenized masonries mechanic behaviour law and an interface law between homogenized blocks. The interface law used "joint elements" including the mortar crack in tensile and shear behaviour. The third step was the 3D computing of the bridge, using a finite element method. Several boundary conditions were explored, blocked or slipping support, to describe the arch bridge behaviour

Structural analysis of a multi-span railway masonry bridge combining in situ observations, laboratory tests and damage modelling

International audienceThe paper presents a structural analysis by means of an orthotropic damage model of a multi-span masonry railway bridge built in the early years of the 20 th century. Its aim is to show how this type of model allows for the current bridge mechanical behaviour under service loads to be assessed and the ultimate load to be forecast. It includes a phase of research on archived documents, an in-situ investigation phase, an experimental phase carried out on core samples in the laboratory, and a computation phase. Among the different calculation steps, a simulation of the bridge history is performed in order to consider the current cracked state induced by support settlement. In a following step, the traffic loads are applied to assess the mechanical behaviour of the bridge under service loads up to failure. The mechanical behaviour of masonry is described by means of an original 3D anisotropic damage model able to consider the opening and the progressive reclosing of localized cracks. The model uses homogenized parameters considering the weakness of the stone-mortar interface. It has the capability to use material pre-damage. The calculation determines the crack pattern induced in the bridge by support displacements and loads. The support displacement study consists of an inverse analysis aimed at determining the actual present state of the structure from the cracking pattern observed on the bridge. The methodology highlights the importance of considering the whole history of a masonry structure when assessing the current state