Méthodologie pour la requalification des ponts en maçonnerie

La conservation du patrimoine ferroviaire et l'exploitation adaptée des ouvrages est une des priorités des gestionnaires des réseaux ferroviaires. Pour cela, il convient de connaître les ouvrages d'art du réseau afin de pouvoir analyser et prédire leur état tout au long de leur vie. Cette thèse a pour objectif de développer une méthodologie globale pour l'analyse des ponts en maçonnerie s'appuyant sur un outil numérique d'aide au diagnostic des pathologies observées. Une étude bibliographique définit la typologie des ponts en maçonnerie avec leurs spécificités et inventorie les pathologies courantes et les différentes méthodes de calcul existantes. Le modèle choisi, dont le développement et l'adaptation aux maçonneries sont présentés dans cette étude, est un modèle d'endommagement avec fissuration anisotrope répartie, intégré dans un code de calcul aux éléments finis. Sans prédisposer les fissures, il est possible de retrouver le faciès de fissuration d'une structure sous diverses sollicitations. La méthodologie globale d'analyse d'un pont en maçonnerie exposée dans cette thèse inclut des investigations sur site : carottages, mesures sous trafic, relevés de fissures. Les carottages permettent de caractériser individuellement les matériaux et une méthode d'obtention des paramètres homogénéisés est proposée afin de modéliser le comportement des maçonneries constituant le pont. La méthodologie préconisée est illustrée à l'aide de l'étude du viaduc de St Ouen. Elle permet notamment de rechercher les mouvements d'appuis à l'origine de fissures observées in situ. La géométrie du pont, les chargements, les conditions aux limites et le post traitement sont facilités par une interface utilisateur développée dans le cadre de cette thèse. Les résultats obtenus sont présentés et discutés.Managers of railways need to preserve the railway heritage and maintain the structures ability to support traffic. Analyzing and predicting the structures behavior is increasingly significant. The research program aims to develop an overall methodology for the masonry arch bridges analysis. It includes a numerical tool for the diagnosis of the observed pathologies. A literature review defines the types of masonry bridges with their specificities and identifies the different existing calculation methods. The developed model is a damage model with distributed anisotropic cracking adapted to masonry and integrated into a finite element code. Without imposed cracks, it is possible to find the cracking pattern of a structure considering various loads. The overall methodology of masonry arch bridges analysis, described in this thesis, includes investigations on site: cores, measurements under traffic, existing crack pattern. The cores are used to characterize individual materials and a method for obtaining homogenized parameters is proposed in order to model the masonry behavior. The proposed methodology is illustrated with the study of a viaduct in St Ouen (close to Paris). It allows investigating different support displacements in order to retrieve the causes of the observed cracks on the structure. The bridge geometry, loads, boundary conditions and post-processing can be easily given using a user interface developed as part of this thesis. The results are presented and discussed

Methodology for masonry arch bridges assessment

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

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

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

Influence of the MASONRY VAULTS building process on their stiffness: Numerical analysis using a homogenised DAMAGE MODEL including mortar joint shrinkage and induced crack re-closure effect

International audienceThe assessment of masonry structures is more and more useful to characterize the behaviour of masonry walls, tower and bridges. The owner of these constructions would like to understand the mechanical performance of their structures. Experiments and computational methods are two essential elements to accurately study and determine the sensitive points of the edifices. This paper presents the numerical modelling of a vault in undamaged and damaged domain with a macro-homogenisation analysis. The importance of considering the building phases in order to determine the actual stiffness of the structure is highlighted. The numerical tool is a continuous finite element model based on an original anisotropic damage model considering the masonry as a homogenised continuous media. The model is implemented in a massive finite element for three dimensional formulation. It computes the localized damage and allows indicating zones of privileged crack opening in the structure. It is able to predict the cracking zones in large masonry constructions without pre-positioning joint elements. It uses a regularization method ensuring an independence of the numerical response from the mesh. The model includes also a re-closure function for cracks. This re-closure function allows simulating the progressive stiffness restitution during the crack re-closure process. The paper focuses on this aspect in relation with the crack induced by restrained shrinkage of joint mortar during the building history. First, a state of the arts is proposed, then the damage model is presented. In order to validate the model and to propose a global methodology, the damage model is applied to analyse a thin masonry vault previously tested in a laboratory. The numerical results are discussed regarding the experimental ones