Search

Numerical and experimental methodologies are presented in order to evaluate thermal and moisture buffering properties of hygroscopic masonry walls composed of unfired clay bricks. An original full-scale instrumented wall is subjected to various transient scenarios on both faces, using a double climatic chamber device. This equipment allows a separated thermodynamic balance in the two rooms for the determination of heat and mass flows through the wall. The development of a coupled heat and mass transfer process implemented in the Cast3M finite element software is outlined as well. The material's input parameters for the model are first identified on samples at a decimeter scale. Among them, a continuous dependence law governing vapor permeability vs. moisture content is established, by exploiting the kinetics of sorption steps in both cubic and half-brick samples. Based on these experimental characterizations, all parameters are introduced for the simulation of a full-scale wall through different scenarios of hydric loading. Comparisons drawn between simulation and the experimental evolutions of moisture and temperature show a good accuracy at this scale. The moisture balance quantities derived in both cells are also verified, proving the model's effectiveness in terms of mass transfer simulation. Finally, the thermal effect of sorption heat is also discussed, experimentally as well as numerically. For realistic scenarios, it is shown to be limited to about 0.5 K.

This paper presents a methodology for probabilistic assessment of masonry vaults bearing capacity with the consideration of existing defects. A comprehensive methodology and software package have been developed and adapted to inspection requirements. First, the mechanical analysis model is explained and validated by showing a good compromise between computation time and accuracy. This compromise is required when probabilistic approach is considered, as it requires a large number of mechanical analysis runs. To model the defect, an inspection case is simulated by considering a segmental vault. As the inspection data is often insufficient, the defect position and size are considered to be unknown. As the NDT results could not provide useful and reliable information, it is therefore decided to take samples with the obligation to minimize as much as possible their number. In this case the main difficulty is to know on which segment the coring would be mostly efficient. To find out, all possible positions are studied with the consideration of one single core. Using probabilistic approaches, the distribution function of the critical load has been determined for each segment. The results allow to identify the best segment for vault inspection.

Timber frame construction with earth brick infill is a sustainable design that is promising in the building construction field. However, cracks form at the interfaces of the bricks and frame with temperature and humidity fluctuations. A geopolymer binder can create stronger bonds between these two materials than traditional mortar, potentially preventing crack formation. This study focuses on the pull-out and shear mechanical behavior of laboratory assemblies of wood, geomaterial binder and two different types of earth brick. The full-field displacements of double-shear test samples were also obtained by digital image correlation (DIC) to better describe and understand the mechanical behavior of the system. The results show that the geopolymer binder provides good adhesion of approximately 1.5 MPa or 2 MPa, depending on the type of brick. Failure localization is also different for each assembly, occurring inside the brick and binder or only inside the binder. This result is confirmed by DIC analysis. The microstructure of the brick has been correlated with the mechanical behavior of the assembly. First results show that the geopolymer binder can be used as a joint in wood and earth masonry.

The interface mechanical behavior in asphaltic pavement structures represents a key parameter for the computational design. Several degradation mechanisms are observed in surface layers due to the de-bonding despite the implementation of tack coats or reinforcing systems. The interface modeling becomes more important in the pavement field during the last ten years, even if this concept is widely studied in composites, masonry structures… Furthermore, the experimental research highlights the sensitivity of the imperfect interface behavior in respect to the underlayer roughness. Due to these concerns, parametrical studies are proposed in this paper, by using a macro scale cohesive zone model. This model allows taking into account the damage behavior of the interface, in pure or mixed mode. Damage mechanisms are governed by internal variables. The numerical results based on a finite element method are compared with experimental tensile and shear data. The geometrical periodic roughness (triangular, crenel) and the mixed mode failure are investigated under monotonic loading. A parametric numerical analysis is presented and shows clearly the roughness influence of these structures.

In the field of construction based on raw clay, there is an active search for less costly stabilising materials, where exploitation of natural resources for construction has become a major concern due to the common problems of degradation of stabilised earth blocks such those used in Ksour constructions. However, despite the technical, economic and ecological advantages reported using the stabilised earth blocks (SEBs), they remain associated with numerous disadvantages due to the lack of research data in this field. This study contributes to a better understanding of the SEBs used in the Kenadsa site, specifically, which are characterised by a mixture of vegetation fibres such as date palm fibres. An analysis is conducted to studying the mechanical properties of specimens prepared from clay collected on the site and mixed to different amounts of fibres and to two different types of stabilisers (cement and/or lime).

This paper focuses on the characterization of the hydric properties of a new construction system in masonry structures composed of extruded earth bricks, geopolymer binder and wooden frame. The study was based on experimental tests such as the sorption desorption isotherms, the water vapor permeability tests on the different materials and the hydric test on a real size wall. The obtained results show the good properties of several materials, particularly in the storage of humidity. The different solicitations applied on the wall allowed to appreciate the ability of a earth brick wall to regulate humidity inside a house.

International audience; In this paper an interface model accounting for roughness and micro-cracks is presented and applied to masonry-like structures. The model is consistently derived by coupling a homogenization approach and arguments of asymptotic analyses. A numerical procedure is introduced and numerical results, based on a finite element formulation, are successfully compared with experimental data , obtained on masonry samples undergoing to shear tests. Finally, a parametric numerical analysis is proposed, highlighting the influence of the roughness features on the interface response.

International audience; Construction system using timber frame with earth brick infill shows the formation of cracks at their interface with the fluctuation of temperature and humidity. Geopolymer binder has been identified to create good adhesion between these two materials. The aim of the study is to characterize the pullout and shear mechanical behavior of laboratory masonry assemblies of wood, geomaterial binder and extruded earth brick. Compression test on the brick were also performed. Full-field deformation of double shear test sample werecarried-out by digital image correlation (DIC) in order to better describe and understand the mechanical behavior. The geopolymer binder show good adhesion properties with mean shear test results around 1.5 MPa and pullout test result around 0.82MPa. © (2013) Trans Tech Publications, Switzerland.

International audience; The aim of this study was to model the mechanical behavior of interfaces in masonry structures. In the first part, the characteristics of the materials and interfaces involved are determined experimentally. In the second part, a model based on the adhesion intensity is developed. This model can be used to describe the interfaces between mortar and full or hollow bricks and to describe the damage occurring in the mortar. The mechanical behavior predicted by this model is compared with previously obtained experimental data. The model is then tested in the case of some classical masonry structures (small walls, diagonal compression tests).