06/10/2020
The Human Resources Strategy for Researchers

Thesis: Kinetics of the deformations of the roof structure of Notre Dame de Paris (M/F)

This job offer has expired


  • ORGANISATION/COMPANY
    CNRS
  • RESEARCH FIELD
    Biological sciences
    Chemistry
    Physics
  • RESEARCHER PROFILE
    First Stage Researcher (R1)
  • APPLICATION DEADLINE
    27/10/2020 23:59 - Europe/Brussels
  • LOCATION
    France › TALENCE,TALENCE
  • TYPE OF CONTRACT
    Temporary
  • JOB STATUS
    Full-time
  • HOURS PER WEEK
    35
  • OFFER STARTING DATE
    30/11/2020

OFFER DESCRIPTION

This thesis work is integrates the action of the Chantier Scientifique Notre DAme. It is based on the collaboration of several laboratories I2M, CITERES, GC2D, LRMH and a team of researchers (Greccau) from the National School of Architecture and Landscape of Bordeaux.
This research brings together expertise in structural calculation and monitoring (monitoring by structural health measurements) of a full-scale model of a span of Notre Dame.

The common calculation of ancient building structures is mainly based on the elastic behaviour of the materials. Using weighting methods (semi-probabilistic approach in design offices), the aim is to anticipate structural behaviours that could affect the safety of the systems and produce excessive strains during the service period. The basis of calculation is most often based on the individual behaviour of components and connections. The overall displacement is estimated by integration without pertinent calibration at the real scale of the structure and without taking into account potential system effects. This approach remains safe in terms of the deformations for recent constructive systems, with relatively simple load reductions and limited possibilities of load transfert. In the field of connections, models are not well informed, which can produce scatters for the predictions of the load rates. As part of cultural heritage, this type of modelling is a starting point for investigation, but the history of loading, the long term behaviour of materials remain a problem to understand better the state of health of these structures and their future evolution.
It is proposed to study a part of the roof structure of Notre Dame de Paris, in order to understand their long term displacements. Historical information (sketches, texts, point and shape surveys) highlight the hyperstatic character of the systems and reinforcement zones. Functional analysis of each element and of each connections is necessary and must be linked to the historical data. The objective of the modelling is to understand the evolution of the load in each component by considering the variability of the materials during construction and then successive repairs.
For this thesis, two strategies are proposed: the first one consists in carrying out an elastic equivalence of the structural behaviour as a function of the load levels in the elements and in the bar connections. This work is based on a study of the sensitivity of the model with its input parameters (bar geometries, frame geometry, elasticity modules, assembly stiffnesses, densities, etc.). The objective is to show which "useful or functional" mechanical properties of the components govern the overall behaviour of the structure. The second strategy is to implement the simplest and most relevant creep laws for structural calculations (in design offices), so as to reproduce the lattice deformations observed by the historical data. The objective is also to develop an "embryonic" structural diagnosis tool able to understand past evolutions and to anticipate future deformations of the structures. This work may be transposed to design offices and expertises for structural diagnosis, in order to complete the recent standard EN 17121: Conservation of cultural heritage - Historic Timber Structures - Guidelines for the On Site Assessment.
Fine modelling of the framework (elements and connections) can provide an additional dimension to the expertise of heritage specialists and design office experts (project management), since variations in displacements are assessed according to long-term loading. Substantial fluctuations of moisture content, caused by the stabilisation of wood used in green construction, or by seasonal variations, can lead to significant strains in elements. The aim is to predict the stresses in the connections according to medieval technology. Damage kinetics leading to excessive deformation of structures may be identified and recorded in relation to historical data. The aim of the thesis is to provide decision support based on the transfer of scientific models for engineering offices. It is also possible to consolidate historical knowledge by integrating the mechanical performance of medieval techniques. Investigations will be made on the characterisation of the most recurrent assemblies in order to analyse the effect of shrinkage and swelling of wood. It would exhibit whether a pre-stressing effect in the connections and possible offsets induced by drying are possible. The analysis of the elastic behaviour up to the failure is propose to understand better medieval connections.
The Bordeaux Academy Rectorate will build a part of the structure of Notre Dame at theend of 2020. In order to calibrate numarical models, a simple and pragmatic monitoring is planned in this thesis work on the site. It will enable the implementation of monitoring techniques. This action can also provide better controlled monitoring systems, thus covering a wider spectrum of monitoring of the existing situation and repairs. The partieal replic of Notre Dame proposed by the rectorate of Bordeaux (scale of 1:1) is an opportunity to make simultaneous research and educational actions, which is an originality of investigation at the level of the national territory. The monitoring should also contribute to a more rational validation of modelling hypotheses. Various measurement technologies will be studied: monitoring of markers (image correlation), local measurements of assembly slippage, theodolite surveys of connection points. A short-term loading strategy will also be implemented (winching or dead mass) to determine the temporal evolution of the instantaneous response of the structure.

More Information

Required Research Experiences

  • RESEARCH FIELD
    Physics
  • YEARS OF RESEARCH EXPERIENCE
    None
  • RESEARCH FIELD
    Biological sciences
  • YEARS OF RESEARCH EXPERIENCE
    None
  • RESEARCH FIELD
    Chemistry
  • YEARS OF RESEARCH EXPERIENCE
    None

Offer Requirements

  • REQUIRED EDUCATION LEVEL
    Physics: Master Degree or equivalent
    Biological sciences: Master Degree or equivalent
    Chemistry: Master Degree or equivalent
  • REQUIRED LANGUAGES
    FRENCH: Basic
Work location(s)
1 position(s) available at
INSTITUT DE MECANIQUE ET D'INGENIERIE DE BORDEAUX
France
TALENCE,TALENCE

EURAXESS offer ID: 565179
Posting organisation offer ID: 17935

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