Engineered wood products, such as cross-laminated timber (CLT), are becoming more popular in the designs of modern sustainable buildings. This increased production of CLT requires more robust, yet less labour-intensive means to assess the material characteristics of whole CLT panels. In exploring ways of improving efficiency, this study explores multivariate image analysis (MIA) via partial least squares discriminant analysis (PLS-DA) machine learning as a means to classify CLT material features. CLT panels underwent nondestructive testing using near-infrared (NIR) hyperspectral imaging and X-ray computed tomography (CT) analysis. MIA was performed on these results to build predictive models for wood features, such as fibre alignment and knot type. The models showed that it was possible to classify material features on the surface of CLT using NIR alone; whilst when combined with X-ray data, it enhanced the predictive ability of material features throughout the CLT volume. These first results from such modelling have the potential to help map the chemical and physical material properties of CLT, improving the manufacturing efficiency of the product and allowing greater sustainability of engineered wood products.

The use of wollastonite as a natural additive for the welding of Scots pine improved the water resistance and shear strength of the welded joint. The X-ray computed tomography images revealed that the welding of Scots pine with wollastonite could postpone crack formation in the welded joints. The specimens welded for a longer time (5 s) had a more uniform distribution of wollastonite particles in welded joints. The microstructure of the wood and the thickness of the wood cell walls also had a great influence on the thickness and strength of the welded joints. Water immersion tests showed that the use of wollastonite in wood joints was able to meet the requirement of resistance to frequent short-term and long-term exposure to water.

This work evaluated the effect of timber quality features on the full-field mechanics of cross-laminated timber (CLT) panels. Panels were individuallysubjected to destructive out-of-plane loading in the principal panel orientation. A digital image correlation (DIC)-based technique was applied fornon-contact full-field measurement and analysis of panel mechanics. The results for 50 layers show that the stiffness of conventional CLT is largelyreduced by the shear resistance of transverse layers. Notably, heterogeneous timber features, such as knots, can reduce the propagation of shear.These results suggest an optimized panel assembly strategy that can be generalized: If shear is dimensioning in an area, e.g. the transverse or thecentral longitudinal layer, the use of knotty timber in that layers can reduce shear propagation. Knots in the compression zone in longitudinal layershave some negative impact, but knots have the largest negative impact in areas of longitudinal layers under tension. Therefore, it is suggested thecurrent grading criteria in the CLT standard be revised to allow the use of more knotty timber in the transverse layers of CLT; doing so could allowa more profitable use of otherwise low-grade timber while producing a stiffer product. The potential of panels constructed according to such anapproach may allow new applications for CLT in timber construction and should be further explored

Today, a large number of people are manually grading and detecting defects in wooden lamellae in the parquet flooring industry. This paper investigates the possibility of using the ensemble methods random forests and boosting to automatically detect cracks using ultrasound-excited thermography and a variety of predictor variables. When friction occurs in thin cracks, they become warm and thus visible to a thermographic camera. Several image processing techniques have been used to suppress the noise and enhance probable cracks in the images. The most successful predictor variables captured the upper part of the heat distribution, such as the maximum temperature, kurtosis and percentile values 92–100 of the edge pixels. The texture in the images was captured by Completed Local Binary Pattern histograms and cracks were also segmented by background suppression and thresholding.

The classification accuracy was significantly improved from previous research through added image processing, introduction of more predictors, and by using automated machine learning. The best ensemble methods reach an average classification accuracy of 0.8, which is very close to the authors’ own manual attempt at separating the images (0.83).

For a development of full-scale finite-element models of large objects in cultural heritage, it can be useful to mechanically test replicas of key parts to identify structural properties which would otherwise not be available. This paper presents full scale tests on a replica of a section of the hull of the 17th century warship Vasa in three load configurations. We focus on determining a displacement of the loaded replica from 3D laser measurements. Two measures were found useful: (i) 3D displacements at well-defined intersections of the wooden replica, and (ii) normal displacements of larger surfaces. Wood surfaces were preferred to steel parts of the rig since the latter showed more scatter in displacement values in their point clouds caused by their reflective properties. The measurements were verified with draw-wire sensors. Some of these sensors were attached to the steel rig supporting the replica and, therefore, measured relative displacements. The scanning data was also useful to quantify the absolute movement of the steel rig supporting the replica, which improved the precision of the measurements of replica deformation. Finally, it is discussed how the replica test results can be used in a model of the entire museum ship.

Energy efficiency is an increasing requirement in the modern construction industry. The building envelope design plays an important role for increasing energy efficiency. The main objective of this study was to evaluate different roof and wall designs for energy efficiency in order to fulfil the future requirement for a sustainable building envelope. The comparative case studies were carried out by calculation and analysis of the different building parts. Of the roofs compared, the koljern-technique worked best. During the analysis of the wall constructs, an exterior wall with polyisocyanurate (PIR) insulation showed the best results. One of the conclusions was that better insulation is needed to meet future requirements for a sustainable building envelope. Another important finding was that the construction industry should be open to new technologies, such as the koljern-technique and PIR-insulation.

Naturally seasoned, kiln-dried, and thermally modified wood has been studied by hyperspectral near-infrared imaging between 980 and 2500 nm in order to obtain spatial chemical information. Evince software was used to explore, preprocess, and analyse spectral data from image pixels and link these data to chemical information via spectral wavelength assignment. A PCA model showed that regions with high absorbance were related to extractives with phenolic groups and aliphatic hydrocarbons. The sharp wavelength band at 2135 nm was found by multivariate analysis to be useful for multivariate calibration. This peak represents the largest variation that characterizes the knot area and can be related to areas in wood rich in hydrocarbons and phenol, and it can perhaps be used for future calibration of other wood surfaces. The discriminant analysis of thermally treated wood showed the strongest differentiation between the planed and rip-cut wood surfaces and a fairly clear discrimination between the two thermal processes. The wavelength band at 2100 nm showed the greatest difference and may correspond to stretching of C=O-O of polymeric acetyl groups, but this requires confirmation by chemical analysis.

This research evaluated the mechanics of cross-laminated timber (CLT) panels with different layer orientations. A total of 20 industrially produced panels, configured with 0° longitudinal layers and transverse layers alternating at either ±45° or the conventional 90°, were tested. Each panel was subjected to destructive out-of-plane testing in the principal panel orientation to evaluate stiffness and strength in bending. Four-point bending tests showed higher stiffness and strength for panels with ±45° alternating layers compared to 90°. A non-contact full-field measurement and analysis technique based on digital image correlation (DIC) was utilised for the main mechanical analysis at different scales. DIC evaluations of 100 CLT panel layers showed that a considerable part of the stiffness of conventional CLT is reduced by the shear resistance of transverse layers. Heterogeneous wooden features, such as knots, reduce the propagation of shear fraction along the layers. These results call into question the present grading criteria in the CLT standard: It is suggested that the current lower grading limit be adjusted for increased value-yield. The overall experimental results suggest the use of CLT panels with a ±45° layered configuration would be beneficial for timber engineering construction. They also motivate the use of alternatively angled layered laminates in design and construction, especially in areas subjected to shear. Based on these results, CLT should be further explored as a suitable product to potentially facilitate the use of wooden panels in more construction applications.

MEÄN SAUNA

- Inventory of old smoke saunas in the Swedish Torne river valley using laser scanning and photogrammetry.

The cultural heritage of the Swedish Torne river valley has been dominated by the Finns. A strong manifestation of this are the numerous smoke saunas on the area. Due to the Lapland war in 1944- 45 the building stock as well as saunas where largely destroyed in Northern Finland. The smoke saunas in the Swedish side were left untouched and are representing the historical type of Finnish sauna culture and sauna buildings in Torne river valley and Lapland.

Every time a smoke sauna is warmed up there is a risk of fire, especially with old saunas. In Torne river valley there is a strong risk of cultural heritage vanishing, since no inventory of these saunas has been done on Swedish side.

In Project MEÄN SAUNA selected old smoke saunas in Swedish Torne river valley will be inventoried by researching of history, laser scanning and photogrammetry.  3D models of sauna buildings will be created and saunas will be classified. The lecture will present at least two old smoke saunas of which one is from 1720. Presentation will contain a brief historical background of saunas as well as explanation and photographs of the site. The methods for laser-scanning and photogrammetry measuring method will be explained. The smoke saunas buildings will be presented by photography, laser-scanning and technical drawings. At the lecture live use of computers and program will be displayed, to make it possible to discover the saunas within the 3D models.

Olle Hagman, PhD, Professor Wood Products Engineering, Luleå University of Technology.

Sara Porzilli, Architect, PhD Europaeus, Post Doctoral Fellow at the University of Oulu.

Markku Seppänen, BSc(Arch), Building Information Modeling Specialist, Oulu.

Mats Winsa, Architect SAR / MSA, Tärendö / Luleå. 

Increasing awareness of sustainable building materials has led to interest in enhancing the structural performance of engineered wood products. This paper reports mechanical properties of cross-laminated timber (CLT) panels constructed with layers angled in an alternative configuration on a modified industrial CLT production line. Timber lamellae were adhesively bonded together in a single-step press procedure to form CLT panels. Transverse layers were laid at an angle of 45°, instead of the conventional 90° angle with respect to the longitudinal layers’ 0° angle. Tests were carried out on 20 five-layered CLT panels divided into two matched groups with either a 45° or a 90° configuration; an in-plane uniaxial compressive loading was applied in the principal orientation of the panels. These tests showed that the 45°-configured panels had a 30% higher compression stiffness and a 15% higher compression strength than the 90° configuration. The results also revealed that the 45°-configured CLT can be industrially produced without using more material than is required for conventional CLT 90° panels. In addition, the design possibility that the 45°-configured CLT can carry a given load while using less material also suggests that it is possible to use CLT in a wider range of structural applications.