Search

Engineered wood products (EWPs) are being increasingly used as construction materials. EWPs are currently being made using synthetic adhesives or metal fasteners, which lead to poor recyclability and reusability. Therefore, this review paper focused on emerging adhesive- and metal-free assembling techniques including wood dowels, rotary-dowel welding, wooden nails, and dovetail joining as alternative ways of making prefabricated EWPs. This will contribute towards green construction and optimising the building process to minimise its negative impact on the environment and its inhabitants, while maximising the positive aspects of the finished structure. The respective advantages and shortcomings will be compared with those of equivalent EWPs. In general, the dowel-laminated timber (DLT) provides sufficient load-bearing capacity and even better ductility than EWPs of equivalent size, but its relatively low stiffness under a bending load limits its application as a structural element. Optimised manufacturing parameters such as dowel species, dowel spacing, dowel diameter, dowel insertion angle, dowel shape, etc. could be studied to improve the stiffness. The improved mechanical properties and tight fitting due to set-recovery of densified wood support its use as sustainable alternatives to hardwood dowels in DLT to overcome problems such as the loosening of connections over time and dimensional instability. The rotary welding technology could also enhance the strength and long-term performance of dowel-type joints, but its poor water resistance needs further investigation. The main obstacles to implementing DLT products in the market are missing technical information and design guidelines based on national codes. [ABSTRACT FROM AUTHOR]

Highlights • Historical timber-framed wall system was investigated under cyclic loads. • Damage progression and post-elastic behaviour was analysed by image-based tracking method. • Plastic deformations and local damage occurred in some joints. • Observations are important for the design of strengthening or repair interventions. Abstract The scope of this paper is to analyse local phenomena associated with the damage progression and post-elastic behaviour of a historical timber-framed wall system under cyclic loads. It was assessed on series of points identified on the wall by processing time-resolved sequences of images. Dedicated methodology of image-based tracking method was developed to analyse local phenomena, such as relative displacements, rotations and deformations in the wall. It was possible to deduce that plastic deformations and local damage occurred in some joints. This type of observation is important for the design of rigorous strengthening or repair interventions. [ABSTRACT FROM AUTHOR]

The influence of the thermal modification process on wood machinability was investigated with four minor species of low economic importance. A set of representative experimental samples was machined to the form of disks with sharp and dull tools. The resulting surface quality was visually evaluated by a team of experts according to the American standard procedure ASTM D-1666-87. The objective quantification of the surface quality was also done by means of a three dimensions (3D) surface scanner for the whole range of grain orientations. Visual assessment and 3D surface analysis showed a good agreement in terms of conclusions. The best quality of the wood surface was obtained when machining thermally modified samples. The positive effect of the material modification was apparent when cutting deodar cedar, black pine and black poplar in unfavorable conditions (i.e., against the grain). The difference was much smaller for an easy-machinability specie such as Italian alder. The use of dull tools resulted in the worst surface quality. Thermal modification has shown a very positive effect when machining with dull tools, leading to a relevant increment of the final surface smoothness. [ABSTRACT FROM AUTHOR]

Wood is one of the oldest building materials and, thanks to its favorable mechanical and technological properties, one of the most versatile. Due to its biological nature, wooden artefacts can undergo some alteration during their service life that can be caused by mechanical, environmental or biological agents. Waterlogged and buried wood elements, present in wetlands and aquatic environments, are subject to modifications at the chemical and anatomical level, which also affect physical and related mechanical properties of the material. The possibility to predict long-term performance and the rate of modification of mechanical/physical properties of the wood material in specific environmental conditions is crucial for proper design and optimal maintenance of submerged load-bearing timber structures. Therefore, prediction models to estimate selected material properties were developed within this study. For this purpose Fourier Transform near-infrared (FT-NIR) spectroscopy and multivariate analysis based on partial least-squares (PLS) were used. The models proved to be effective to predict selected dynamic and physical parameters of waterlogged samples. However, in order to include the effect of water saturation in the material on site further research is indispensable. The possible detrimental effect on wood mechanical properties of waterlogging in differing environmental conditions is also discussed in this paper. Dynamic tests were performed on samples of two species, Quercus robur L. and Pinus sylvestris L., after 8 years of deposition in two differing sites. Additionally, the results obtained from fresh and archaeological samples were compared. No significant effects have been observed due to the depositional environment after short-term waterlogging. A more remarkable difference in the rate of the modification of dynamic and physical (density) properties can be attributed to differing natural features of the tested wooden species. It may be concluded that, in order to ensure a longer service-life of waterlogged timber structures, original wooden material should be properly selected, with regard to species, growth conditions, and log characteristics. [ABSTRACT FROM AUTHOR]

Arctic driftwood has reached the coast of Iceland for centuries. This material was used by the inhabitants of the island as a building material for houses, boats, churches and pasture fences. Nowadays, the driftwood is used in the furniture industry, for the finishing of internal and external walls of buildings and also by artists. The properties of driftwood differ to that of original resource due the long-term effects of exposure to Arctic Sea water and ice. This process can be considered as a natural modification, even if its effect on various wood properties and the potential use of driftwood are not yet fully understand. This research is focused on the comparison of cutting forces measured for Siberian larch (Larix sibirica L.) from Siberia provenance and driftwood found on the coast of Iceland. The cutting forces were determined directly from the cutting power signal that was recorded during the frame sawing process. A new procedure for compensation of the late/early wood ratio variation within annual rings is proposed to homogenize mechanical properties of wood. It allows a direct comparison of machinability for both types of larch wood investigated (driftwood and natural). Noticeable differences of normalized cutting force values were noticed for both wood types, which were statistically significant for two set values of feed per tooth. These results provide a new understanding of the effect of the drifting process in the Arctic Sea (natural modification) on mechanical and physical properties of wood. Such a natural modification may influence transformation processes of driftwood as well as performance of the coating systems applied on its surface. [ABSTRACT FROM AUTHOR]