Studies on hygrothermal performance of wood elements in building constructions–remarks on methodology

In general, building constructions containing wood elements are moisture sensitive. To increase the knowledge about their hygrothermal performance accompanied with assessments of risk of mold growth and other degradation mechanisms a set of analytical methods is typically used: standard calculation or more advanced mathematical models, laboratory measurements and field observations. Nevertheless, in some cases such approach seems not to be sufficient. Full size testing under controlled and long-time stable boundary conditions is needed in order to get more complex picture about the real performance and risks. In the first part, the paper informs about hygrothermal problems and mold growth modelling. The key part of the paper deals with methodology and technique available at University Centre for Energy Efficient Buildings: Full size façade openings for placing different assemblies of building envelopes with wood elements and facility with crawl-space type foundations. Furthermore, laboratory experiments and measurements together with in-situ monitoring as example are presented. The paper discusses combinations of advanced modelling used for design of experiments on one hand with expected results from full size controlled testing on the other hand. Classification of mold growth risk can represent an efficient way of expression of overall quality in this respect. First results are presented here for illustration. Paper concludes that coordinated combination of different research techniques can bring new knowledge in understanding the processes leading to deterioration of wood elements in building construction.

Some orthotropic elastic properties of Fagus orientalis as influenced by moisture content

The aim of this study was to investigate the influence of moisture content on some orthotropic elastic properties of Oriental beech (Fagus orientalis). The elastic properties investigated include EL, ER, ET, νLR, νLT, νRL, νRT, νTL and νTR under compression. Compression strength in all orthotropic directions was also studied. Specimens were cut from sapwood of beech logs and sorted into four matched MC groups. Clear wood samples were conditioned at 20°C and 50, 65, 85, 95 % RH and subjected to compression tests. A digital image correlation technique was used to capture the strains during testing. Young modulus, Poisson ratios, and compression strength were calculated and compared for all orthotropic directions. Results indicated that Young modulus and compression strength of the samples tested were strongly affected by moisture content. Poisson rations seem to less sensitive to the MC changes.

Moisture at contacts of timber-concrete element

The subject of the article is to monitor the changes of moisture on the contact surface concrete and timber part of the composite timber-concrete beam. The moisture directly affects the properties of timber and causes its volume changes and degradation processes. These effects reduce of durability and load capacity of the structures. The beam was placed at the exterior. The observed contacts of the beam are often critical on real structures, as it is difficult to repair and maintenance in the case of increasing moisture or intrusion of dirt. The experiment was used to monitor and evaluate the dependence of changing moisture in contacts depending on ambient environmental conditions.