Author: Shuang Peng

Publisher:

Published: 2020

Total Pages: 0

ISBN-13:

In France, a great number of historical patrimony, consists of stone masonry building, the conservation of this patrimony is a cultural and economic issue. However, the destructive tests are limited in some types of buildings, particularly at a strong architectural heritage value. The need expressed by client and the diagnostic company concerns the lack of a reliable methodology for structural assessment at material and structural scale. Therefore, it is necessary to develop an approach which can combine the CND with the mechanical calculation. This thesis tries to answer three questions: (i) how to improve the reliability of material characterization by non-destructive tests at the structures; (ii) how to improve defect detection, localization and evaluation in material; (iii) how to improve the modeling of mechanical behavior based on CND auscultation. The first objective of this thesis is to improve the reliability of assessment of material characteristics in stone masonry structure by non-destructive techniques (mechanical properties of stones and joints). The proposed methodology will take into account the uncertainties related to: (i) the measurement procedure by CND device; (ii) the material variability constituting the masonry (stones and mortar joints); (iii) the water content which represents a significant bias in the measurement of CND. The main objective of this step is to establish, based on the constitutive material of structure, possible relations between the measurable magnitude by CND and the physical and mechanical properties. The combination of these data will enable to implement an inverse tool, using the CND measurements to deduce the properties of constitutive material of structure. Some methods, as ultrasound, electricity and electromagnetics, which require further understanding, are envisaged to be used in this stage. The second part of this thesis aims to assess the potential of the CND acoustic and electromagnetic methods for the detection of defects, particularly at the level of mortar joints. An active and passive CND instrumentation will be implemented during the characterization test of mortar joints and a validation test will be also proposed at structural scale (masonry wall). In order to realize this objective, an experimental campaign of characterization and validation which will be carried out within the CIFRE thesis of Vincent VENZAL, in collaboration with AIA Ingénierie (thesis started in September 2016). These masonry walls (stones of Frontenac assembled by the lime mortar joints), constructed at demi scale, will be subjected to a vertical loading and tested in shear until the ruin. Once the nondestructive method of mechanical characterization of limestones is validated, a mapping of mechanical properties in structure cans be obtained by non-destructives measurements. This enable to identify the variability of mechanical characterization for the different studied zones and also within these zones. Firstly, this variability could probably be used to identify the partial safety coefficient of masonry in situ by verification in Eurocode 6. Secondly, a study of sensibility of variability of these mechanical properties would be realized by finite element method (damage law). These numerical mechanical tests with random draw of mechanical characteristic in relation with the variability obtained in site lead to (i) identify the real homogenized stress of elements in masonry at the structural scale and (ii) study the scale effect on the highly heterogonous structure.