Volume 12 Issue 1

This paper deals with the change of roughness of compressed beech wood. Effects of temperature, pressure, and time on the results of pressing were examined. The surface roughness of beech wood in longitudinal and transversal directions was evaluated. Roughness was described by Ra. A contact method was applied. The results show that by increasing pressure, time, or temperature, the surface roughness of beech wood decreases. The highest roughness reduction occurred at the temperature of 150 °C, pressure 4 MPa, and time 20 min.

This article deals with the effects of various parameters on the shear bond strength (SBS) of glued wood. A four-factor analysis showed that the combination of only non-densified wood pieces achieves higher shear bond strength values than densified ones. In this case, only the piece combination was a significant factor. The other factors (glue type, wood species, and number of loading cycles) had no significant effect. Although the differences were not large, a higher SBS was achieved in beech wood glued with polyvinyl acetate (PVAc) glue. Glued wood consisting of the combination of densified and non-densified pieces had slightly lower SBS values. In this case, all the factors were statistically significant. Beech wood had a more significant impact on the SBS than aspen wood. The effect of the type of glue showed an opposite trend than that in the previous variant, i.e., a higher SBS was achieved with polyurethane (PUR) glue. Wood subjected to cyclic loading had slightly higher SBS values than non-cyclically loaded wood. The degree of densification had no significant effect. Glued wood composed entirely of densified pieces showed greater SBS variation between versions.

Binderless boards were produced from bamboo particles through a molding pressing process. The boards were investigated for the chemical and structural changes of lignin and their mechanical strengths to evaluate the mechanism of self-bonding. The structural transformations of milled wood lignin (MWL) obtained from raw bamboo and molding pressed bamboo boards were investigated by Fourier transform infrared (FT-IR), gel permeation chromatography (GPC), quantitative 13C-NMR spectra, two-dimensional heteronuclear single quantum coherence (2D-HSQC) spectra, 31P-NMR, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) techniques. Both molding press temperature and time affected the distribution and abundance of typical lignin linkages (β-O-4′, β-β′, and β-5′), as well as the S/G ratios of the lignin, demethoxylation, and the contents of attached molecules (PCE). In addition, a decrease in aliphatic OH and an increase in phenolic hydroxyl groups occurred in lignin as molding pressing proceeded. The optimal internal bonding strength (0.98 MPa) of the bamboo binderless board was obtained under the condition of 180 ºC for 20 min. Although the lignin obtained under this condition was structurally similar to the raw MWL, the decreased molecular weight, increased phenolic hydroxyl groups, and observable glass-transition temperature (thermal softening of lignin) provide some evidence to explain the acceptable internal bonding strength.

Steel and concrete are traditionally used as structural materials for non-residential and multi-housing buildings. However, wood can meet the same structural property requirements, and a variety of multi-story buildings have recently been built all over the world using this key material. In this study, the main motivations and barriers to wood adoption for structural uses in non-residential buildings are highlighted, based on an analysis of grey literature concerning some well-known buildings and on scientific literature. The motivations found were linked to sustainability, lack of expertise, costs, rapidity of erection, and aesthetic of wooden structures. In contrast, the barriers preventing its use encompass building code implementation, technology transfer, costs, material durability and other technical aspects, culture of the industry, and material availability. Furthermore, an analysis of non-residential timber building meeting minutes for nine projects is also presented to support the identification of problems and concerns related to site assembly issues, the conception of the building, the scheduling, and stakeholders’ relationships. With a better understanding of the expectations and challenges concerning wood usage in non-residential construction projects, companies will be able to adapt their business models and use the resource even more in the future to develop innovative structures.