Monika Woloszyn

Identification of the hygrothermal properties of a building envelope material by the covariance matrix adaptation evolution strategy

This paper proposes the application of the covariance matrix adaptation (CMA) evolution strategy for the identification of building envelope materials hygrothermal properties. All material properties are estimated on the basis of local temperature and relative humidity measurements, by solving the inverse heat and moisture transfer problem. The applicability of the identification procedure is demonstrated in two stages: first, a numerical benchmark is developed and used as to show the potential identification accuracy, justify the choice for a Tikhonov regularization term in the fitness evaluation, and propose a method for its appropriate tuning. Then, the procedure is applied on the basis of experimental measurements from an instrumented test cell, and compared to the experimental characterization of the observed material. Results show that an accurate estimation of all hygrothermal properties of a building material is feasible, if the objective function of the inverse problem is carefully defined.

Proper generalized decomposition for solving coupled heat and moisture transfer

This paper proposes a reduced order model to simulate heat and moisture behaviour of material based on proper general decomposition (PGD). This innovative method is an a priori model reduction method. It proposes an alternative way for computing solutions of the problem by considering a separated representation of the solution. PGD offers an interesting reduction of numerical cost. In this paper, the PGD solution is first compared with a finite element solution and the commercial validated model Delphin in an 1D case. The results show that the PGD resolution techniques enable the field of interest to be represented with accuracy, with a relative error rate of less than 0.1%. The study remains in the hygroscopic range of the material. As the numerical gain of the method becomes interesting when the space dimension increases, this resolution strategy was then used on a 2D multi-layered test case. The dynamics and amplitude of hygrothermal fields are perfectly represented by the PGD solution. Temperature and vapour pressure modelled with PGD can be used for post-processing and analysing the behaviour of an assembly.

Characterisation of concrete and mortar cracking by digital image correlation and acoustic emission

Cracks and defects in construction materials can cause an increase in their moisture permeability, and accentuate their degradation. In order to accurately assess the durability and the overall performance of building facades, one must dispose of a reliable method for the identification of the damage state of such materials. The present work aims at developing a methodology for the detection and monitoring of damage and fractures in building materials. Digital image correlation and acoustic emission monitoring were simultaneously performed during tensile loading tests of fibre-reinforced mortar samples. The optical technique was found able to reveal all ranges of cracks, from microscopic to macroscopic, and an image-processing procedure was conducted as to quantify their evolution in the course of the degradation of the samples. It was also found that the acoustic activity could be related to the optical measurements in terms of damage quantification and localisation.

Hygric and Thermal Insulation Properties of Building Materials Based on Bamboo Fibers

This study focuses on manufacturing bio-insulation fiberboards from bamboo fibers and bone glue, modified with sodium lignosulfonate. The microstructure of these boards is investigated by mercury intrusion porosimetry. The porosity and average pore size of boards are decreased; however, the specific pore surface is increased with the presence of bio-glues in boards. The hygric properties are examined through kinetics of water vapor sorption at equilibrium states. The thermal conductivity and bending properties are also studied. The thermal conductivity is dependent on relative humidity levels and moisture content of the fiberboards. The bending property is increased with 30% (w/w) of mixture glue between bone and sodium lignosulfonate in boards.