Thermal instability is the one of the most important disadvantages of wood since it begins to decompose at a low temperature (˃110 °C). Many scientists, past and present, have conducted studies aimed at improving the thermal stability of wood. The aim of this study was to impregnate wood with nano-sized boron nitride (NBN) to improve its thermal stability and to investigate the changes in the properties of Scots pine, Ash and Iroco woods after the impregnation. The effects of the impregnation with NBN also were investigated on the heat-treated woods. The impregnation was conducted with using empty-cell method (the Rueping method) in a chamber under a pressure of 6 bars for 1 hr. Densities at 0% and 12% moisture content (MC), mechanical properties, color changes, thermal stability, and scanning electron microscopy (SEM/EDX) analysis were determined. The test results showed that the impregnation of wood with NBN increased generally the flexural strength and elasticity of modulus at bending, but the NBN impregnation decreased generally the compression strength except for ACI, ATWI, IC, and ICI. It was also determined that the changes in density and color were statistically different after the impregnation. According to the SEM/EDX results, deposits of nano-sized boron nitride were found inside the cell wall and on the pits. But the deposits were also determined in inside structure of the wood with EDX analysis. Thermal stability in T10% and T50% of wood was found to improve after the impregnation with NBN. TG/DTG and DTA values for some samples were found to fluctuate due to the heterogeneous dispersion of the NBN in the wood.

Cellulose nanofibrils (CNFs) and nano clay (NC) were selected to determine effects of different fillers on the characterization of poly(vinyl acetate) (PVA). Characterizations of the PVA composites obtained were studied by thermogravimetric analysis (TGA/DTG), scanning electron microscopy (SEM) and the lap joint shear strength (LJSS). The morphological studies revealed that some clumpings were observed in SEM pictures for 1%, 2%, and 4% wt loadings for CNFs and NC fillers. Dispersed particle orientation morphology and the wave sheets appear to be uniformly distributed on the surface of the composites. As seen as the effects of fillers on the thermal stability, the results showed that NC has a greater effect than CNFs, depending on the loading rates of fillers. Lap joint shear strength generally increased after adding CNFs and NC to PVA matrix. Thus, it can be said that PVA has higher bonding performance and can be used in applications requiring higher bonding strength.

Monitoring displacements and weather impact of complex structures such as a large cable stayed footbridge generates large amount of data. In order to extract, visualize and classify health-monitoring data to get a better comprehension multivariate statistical analysis is a powerful tool. This paper is a screening to evaluate if principal component analysis is useful on health monitoring data. Principal component analysis (PCA) and projections to latent structures by means of partial least squares (PLS) modeling were used to achieve a better understanding of the complex interaction between bridge dynamics and weather effects. The results show that principal component analysis (PCA) give good overview of the collected data, and PLS modeling show that winds from east and west best explain bridge movements.

Construction of modern timber bridges has greatly increased during the last 20 years in Sweden. Wood as a construction material has several advantageous properties, e.g., it is renewable, sustainable, and aesthetically pleasing, but it is also susceptible to deterioration. To protect wood from deterioration and ensure the service life, the wood is either treated or somehow covered. This work evaluates a technology to monitor the moisture content in wood constructions. Monitoring the moisture content is important both to verify the constructive protection and for finding areas with elevated levels of moisture which might lead to a microbiological attack of the wood. In this work, a timber bridge was studied. The structure was equipped with six wireless sensors that measured the moisture content of the wood and the relative humidity every hour. Data for 744 days of the bridge are presented in this paper. Results show that the technology used to monitor the bridge generally works; however, there were issues due to communication problems and malfunction of sensors. This technology is promising for monitoring the state of wood constructions, but a more reliable sensor technology is warranted continuous remote monitoring of wood bridges over long periods of time.

In this paper, a series of experimental bending and compression tests were performed on cross-laminated timber (CLT) products with ±45° alternating layers, to evaluate their performance against conventional panels of 90° orientation. Engineered wood products, such as CLT with ±45° alternating layers can provide opportunities for greater use in larger and more sustainable timber constructions. A total of 40 panels, manufactured in an industrial CLT production line with either of these two configurations, were tested and compared. Panels were evaluated in bending tests n=20 and the remaining ones in compression tests. Results showed that 35% increased the strength in the four-point bending tests for panels containing ±45° alternating layers compared with the 90° alternating layers. Compression strength was increased by 15%. Stiffness increased by 15% in the four-point bending and 30% in the compression. The results indicate that CLT containing ±45° alternating layers has increased strength and stiffness compared to 90° alternating layers. These findings suggest that further developments in CLT are feasible in advanced building applications.

Bending tests were conducted with cross laminated timber (CLT) panels made using an alternating layer arrangement. Boards of Norway spruce were used to manufacture five-layer panels on an industrial CLT production line. In total, 20 samples were tested, consisting of two CLT configurations with 10 samples of each type: transverse layers at 45° and the conventional 90° arrangement. Sample dimensions were 95 mm × 590 mm × 2000 mm. The CLT panels were tested by four point bending in the main load-carrying direction in a flatwise panel layup. The results indicated that bending strength increased by 35% for elements assembled with 45° layers in comparison with 90° layers. Improved mechanical load bearing panel properties could lead to a larger span length with less material.

Wood is a pure, sustainable, renewable material. The increasing use of wood for construction can improve its sustainability. There are various techniques to assemble multi-layer wooden panels into prefabricated, load-bearing construction elements. However, comparative market and economy studies are still scarce. In this study, the following assembling techniques were compared: laminating, nailing, stapling, screwing, stress laminating, doweling, dovetailing, and wood welding. The production costs, durability, and ecological considerations were presented. This study was based on reviews of published works and information gathered from 27 leading wood product manufacturing companies in six European countries. The study shows that the various techniques of assembling multi-layer wooden construction panel elements are very different. Cross laminated timber (CLT) exhibited the best results in terms of cost and durability. With regard to ecological concerns, dovetailing is the best. Taking into account both durability and ecological considerations, wooden screw-doweling is the best. These alternatives give manufacturers some freedom of choice regarding the visibility of surfaces and the efficient use of lower-quality timber. CLT is the most cost-effective, is not patented, and is a well-established option on the market today.

A novel fire-resistant adhesive made from polyvinyl alcohol, urea, phosphoric acid, and starch was demonstrated for use as a binder and fire retardant to produce ultra-low density fibreboard (ULDF) with clear environmental benefits. The results from Fourier transform infrared spectroscopy showed the presence of chemical bonding between fire- resistant adhesives and ULDFs. The limiting oxygen index (LOI), combustion behaviour, and thermal stability were characterized using a LOI text, cone calorimeter, and thermal analyzer, respectively. The results demonstrated that the LOI value of the fire-retardant ULDF can reach up to 34.2 with 300 mL of fire-resistant adhesive. It was established that the additive noticeably reduced the peak of heat release rate, total heat release, and total smoke release of ULDF. Their morphologies after combustion were elucidated using a scanning electron microscope, and a char layer in the condensed phase was observed. Thermal analysis showed that the thermal stability of ULDF improved dramatically and the residual weight increased 4-fold, to 48.32%. Therefore, such ULDFs will be tremendously attractive as renewable, sustainable, and bio-based insulating materials.

The preparation conditions of complex fire-retardant (FR) agents containing boron compounds (BF, X1), nitrogen-phosphorus compounds (NPF, X2), silicon compounds (SF, X3), and halogen compounds (HF, X4) for ultra-low density fiberboard (ULDF) were optimized using a response surface methodology. The effects and interactions of X1, X2, X3, and X4 on the fire properties of ULDF were investigated. An optimum char yield of 61.4% was obtained when the complex fire-retardant agents contained 33.9% boron, 27.2% nitrogen-phosphorus, 15.0% silicon, and 28.6% halogen. Compared with control fiberboard (CF), the heat release rate (HRR) profiles of all fiberboards with FRs were reduced. The peak HRR reduction in BF and NPF was more pronounced than for SF and HF at this stage. And the mixed fiberboard (MF) had the lowest pkHRR of 75.02 kW m−2. In total heat release (THR) profiles, all fiberboards with FRs were lower than the CF. Unlike the HRR profiles, HF had the lowest THR profile of 15.33 MJ/m−2. Additionally, Si compounds showed greater effectiveness in preventing ULDF mass loss than BF, NPF, and HF. MF showed the highest residual mass (40.94%). Furthermore, the synergistic effect between four FR agents showed more significant results in ULDFs.

The poly-aluminum silicate sulphate (PASS) for ultra-low density fiberboard (ULDF) was synthesized in the mixed aqueous solution of sodium silicate and aluminum silicate by sol-gel method. Their preparation conditions were optimized by using a response surface methodology. The effects and interactions of Si/Al molar ratio (X1), pH value (X2) and temperature (X3) on internal bond strength of ULDF were investigated. Research showed that the optimum internal bond strength (10.23 ± 0.64 kPa) was obtained under Si/Al molar ratio of 2:1, pH value of 8, and 50oC. Analyses of the Fourier transform infra-red spectroscopy spectra confirmed that Al-O-Si bonds were formed between polysilicate and Al or its hydrolysate. The particle size analysis showed that the average size of PASS was 7.52 μm. And the part of PASS entered the cell wall and made a contribution to the improvement of mechanical properties of ULDF.

To clarify how the mechanical properties of ultra-low density fiberboards (ULDFs) affected by Si-Al molar ratios, they were prepared with different Si-Al molar ratios. Microstructure and mechanical properties of the ULDFs were tested using scanning electron microscope, energy dispersive spectroscopy, X-ray photoelectron spectrometer, Fourier transform infrared spectrometer, X-ray diffractometer, and microcomputer control electronic universal testing machine. The results showed that Si and Al component were uniformly distributed on the fibers’ surface and the bond of Si-O-C was formed. The different microstructures and relative densities were presented with different Si-Al molar ratios. The results of the modulus of elasticity (MOE), modulus of rupture (MOR) and internal bond strength (IB) were also significantly affected by different Si-Al molar ratios; and their maximum values of 20.78, 0.17, and 0.025MPa were obtained while Si-Al compounds with Si-Al molar ratio of 2:1 was added.

The hybrid composites of polyvinyl alcohol (PVA)/Si-Al were synthesized to improve the thermostability and mechanical properties of ultra-low density fiberboard (ULDF). Their physical and chemical properties were tested by using scanning electron microscopy, Fourier transform infrared spectrometry, X-ray diffractometry, thermogravimetric analysis (TGA), and a microcomputer control electronic universal testing machine. Microstructure results indicated that the distribution of inorganic fillers on the surface of ULDF was improved by the PVA. Analysis of chemical bonds and crystallinity of materials showed that part of the PVA reacted with Si-Al sol, and the other was physically crosslinked in the composite. The thermostability of ULDF decreased with the increasing content of PVA, but the mechanical properties increased. Combined with the TGA and mechanical properties results, a reasonable content of PVA (30%) was obtained. Under this condition, the modulus of rupture, modulus of elasticity, and the internal bond strength of ULDF were 0.35, 24.86, and 0.038 MPa, respectively

Response surface methodology was used to optimize the refining conditions of Pinus massoniana cellulose fiber and to improve the mechanical properties of ultra-low density plant fiber composite (ULD_PFC). The effects and interactions of the pulp consistency (X1), the number of passes (X2), and the beating gap (X3) on the internal bond strength of ULD_PFC were investigated. The results showed that the optimum internal bond strength (91.72 ± 2.28 kPa) was obtained under the conditions of 8.0% pulp consistency, two passes through the refiner, and a 30.0 μm beating gap. Analysis of the physical properties of the fibers and handsheets showed that the fibrillation of fibers with optimum refining conditions was improved. Also, the tear index of the optimal specimen was 13.9% and 24.5% higher than specimen-1 with a lowest beating degree of 24 oSR and specimen-6 with a highest beating degree of 73 oSR, respectively. Consequently, the optimal refining conditions of the fibers are valid for preparing ULD_PFCs.

This study investigates the application of mesoporous aluminosilicate material with hierarchical porosity to ultralow density wood fiber composite (ULD_WFC) for improving their mechanical properties. A 300 nm thickness Si–Al inorganic film was applied to the surface of the fibers. The mesoporous aluminosilicate material with many mesopores ranging from 2 to 20 nm was obtained. Their total pore volume and Brunauer–Emmett–Teller surface area were 0.193 cm3/g and 355.2 m2/g, respectively. Thermogravimetric analysis indicated that the thermostability of ULD_WFCs was affected by Si–Al compounds. But the residual weight of ULD_WFC with Si–Al compounds was 23.87% greater than composite without Si–Al compounds. The X-ray diffraction analysis indicated partial conversion of SiO2 to α-SiC. These conditions attributed to improving the mechanical properties of ULD_WFC. The modulus of elasticity, modulus of rupture, and internal bond strength of composite with Si–Al compounds increased by 547.4%, 240.0%, and 400.0%, respectively, as compared with uncoated ULD_WFC.

To obtain a suitable refining process for Pinus massoniana cellulose fibers (PMCF) and China fir cellulose fibers (CFCF), the effects of the beating gap and the pulp consistency on the physical properties and the morphology of the two cellulose fibers were investigated. The results showed that the physical properties of the PMCF and the CFCF were well affected by the beating gap and the pulp consistency. The CFCF showed a smaller weight-average length and width than that of the PMCF. The CFCF exhibited smaller weight-average length, width, and kink index than the PMCF. It is easy to get the high beating degree, indicating it is more easily to be refined. Additionally, the tensile index and burst index of PMCFP and CFCFP increased with increasing beating degree, while the tear index decreased. Compared to the CFCF, the paper made from PMCF had superior strength properties. Consequently, the PMCF was suitable for refining with a high pulp consistency and a medium beating gap, whereas the CFCF had a medium pulp consistency and a big beating gap.

To improve the mechanical properties of ultra-low density plant fiber composite (ULD_PFC), a suitable beating process to improve the fibrillation of cellulose fibers and maintain their length was investigated. The physical properties of cellulose fibers and papers, surface chemical bonds, and internal bond strength (IB) of ULD_PFCs were analyzed. The results showed that the beating degrees, degree of fibrillation, and fiber fines increased with the decreasing of beating gap, except for the fiber weight-average length, width, kink index, and curl index. The tensile index and burst index of paper showed an increasing trend with an increase in beating degree, while the tear index showed a decreasing trend. FTIR results showed that intermolecular and intramolecular hydrogen bonds in ULDF were broken. A suitable beating gap of 30 μm with a beating degree of 35 °SR was obtained. The corresponding IB was 50.9 kPa, which represented an increase of 73.1% over fibers with a beating degree of 13 °SR.

Rising interest in using wood in non-residential multi-story building structures opens up new opportunities for utilising low-grade hardwoods. The primary objective of this study was to evaluate the geographic variation in modulus of elasticity (MOE) and modulus of rupture (MOR) of sugar maple and yellow birch wood in relation to stand and tree characteristics for two regions in New Brunswick, Canada. Mixed effects statistical models were developed to test the effects of stand, tree, and wood sample variables. A second objective was to examine geographic variation in heartwood discolouration in relation to stand and tree characteristics. Between-tree differences (trees nested within sites) accounted for 44% and 35% of the total variation in yellow birch (MOE and MOR, respectively) and for 69% and 60% of total variation in sugar maple. The fixed effects explained only a very small part for the variation in MOE and MOR in the sugar maple data (10% for MOE and 5% for MOR). For sugar maple, mechanical properties (MOE and MOR) at 50% of the radius were considerably lower than those close to the bark, but this radial variation was not noteworthy for yellow birch. Discoloured heartwood proportion had no significant effect on wood mechanical properties.

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.

The influence of the surface treatment of raw medium-density fiberboard on the properties of 1st ultraviolet putty coating film and the effects of primer coating arrangement on the qualities of 1st ultraviolet primer film were investigated. With regard to surface roughness and the recorded adhesion of the coating film, there were significant variations when the surface treatment was modified or when the coating arrangement was changed. The findings led to the conclusion that there was a close relationship between the surface treatment as well as the coating arrangement and properties of the coating film.

The key point of design for timber-concrete composite structure is to ensure the reliability of shear connectors. This study examined the mechanical properties of bolt-type connectors in timber-concrete composite structures theoretically and experimentally. The theoretical study was based on the Johansen yield theory (European Yield Model). Push-out specimens with different bolt dimensions were tested to determine the shear capacity and slip modulus. According to the experimental results, bolts yielded without timber or concrete cracks when the stiffness of bolts was not very great. The shear capacity and slip modulus of the bolt connectors were directly proportional to the diameter of the bolt. The strength of concrete was found to significantly affect the shear capacity of bolt connectors. Comparison between the theoretical and the experimental shear strength results showed reasonable agreement. 

The commercial feasibility of sawmilling mainly depends on the expected productionyield. At the same time, the choice of sawing method is one of primary factors affecting yield.Therefore, choosing a reasonable sawing method is also necessary in small-diameter logs sawingprocess. In this study, a novel sawing method was proposed, and a comparison was made betweenthe volume yield for the most common sawing method in China, and the yield produced by anovel sawing method. This study shows that hexagon sawing give higher yield than the othersawing methods. The mean yield for the whole diameter range is: 82.7 % for hexagon sawing,53.3 % for live sawing, 56.7 % for hexagon sawing, 63.2 % for hexagon sawing.

Hexagonal glue-laminated timber with large cross-sections, made from small diameter logs, was studied. Effects of relative humidity variations on the moisture-induced stresses were investigated to evaluate how the prediction model compared to a real outcome. The test samples were exposed to an environment with relative humidity variations from 80% to 30%. The moisture content inside the samples was measured via X-ray computed tomography scanning. A moisture transport and a hygromechanical finite element simulation model was used for the prediction of moisture content and resulting stress distribution. The results from both the test and simulation showed that the moisture content in the edge angles of the samples dropped rapidly due to a large moisture diffusion rate. The moisture gradient was generated via a different moisture transfer rate at the inner and external parts of the samples. The maximum stress perpendicular to the grain in the simulation was 8 MPa and was located at the surface near the corners. This stress peak caused cracking according to the model, which was also seen in the test samples. The results for the measured moisture content agreed with the simulated results and this indicated that the moisture transfer model was adequate for simulation.

A means for selecting the optimal process parameters for the laser cutting of recombinant bamboo, based on the design of experiments (DOE) approach, was presented. Recombinant bamboo of thicknesses of 5, 10, and 15 mm was cut with a CO2 laser. The parameters investigated were the laser power, air pressure, and cutting speed. The results were compared using a number of process responses which define the efficiency of the cut, including the upper kerf (UK) width, lower kerf (LK) width, and the ratio of upper-to-lower kerfs. Mathematical models were developed to establish the relationship between the process parameters and the kerf parameters; special graphs were drawn for this purpose. Finally, a numerical optimization was performed to find out the optimal process settings at which the upper-to-lower kerf ratio would be minimized.

To clarify how the fire performance of ultra-low density fiberboard (ULDF) can be improved by complex fire-retardants, the limiting oxygen index (LOI) and microstructure of ULDFs with different additive amounts of complex fire-retardants was analyzed. The char yield, chemical bonding, and thermostability of ULDFs treated by different temperatures were also tested. Results showed that the LOI values and compactness of ULDFs were increased with increased amounts of fire-retardants. Three steps of char yield curves in control fiberboard (CF) and mixed fiberboard (MF) were apparent. The preliminary degradation in lignin and cellulose of CF occurred at 300 °C. The cellulose had completely decomposed at 400 °C, but in the case of MF, the lignin and cellulose were not completely decomposed at 400 °C. It was shown that there are different ways to improve the fire resistance of ULDF using boron, nitrogen-phosphorus, silica, and halogen-based fire-retardants. The fiberboard with silicium compounds had the lowest mass loss in three stages and total mass loss. Compared with CF, MF had a lower mass loss. Furthermore, the exothermic peak for MF at around 400.0 °C was decreased, indicating that the fire resistance of ULDF was improved by the complex fire-retardants. 

To evaluate the quality of laminated particleboard, a typical type of laminate was used in laminating particleboard with operational parameters similar to industry operation. Pull-off tests using Elcometer 510 were conducted. In addition, panel vertical density profiles (VDP) and the pH of particleboard at different layers were tested. The results showed that the laminated panel bonded by polyvinyl acetate (PVA) glue had higher pull-off strength than that of the phenol formaldehyde (PF) glue within corresponding sanding thickness. Sanding off 0.0762 mm resulted in higher pull-off strength than sanding off 0.0254 mm. The laminates had the highest pull-off strength when the PB were sanded off 0.0762 mm and glued by PVA. This has provided a solution to improve lamination pull-of strength for industry. The test results have also shown that the laminated panels produced in the manufactures have the potential to be improved. It also indicates that Elcometer 510 is a good tool to evaluate the particleboard lamination quality.

Co-polymer systems of methylene diphenyl diisocyanate (MDI) and phenol-formaldehyde (PF) resins with different molecular weights were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The FTIR and TGA coupled with differential thermogravimetric (DTG) results showed that higher molecular weight of PF resins not only promoted the reaction of isocyanate and PF co-polymer system, but also resulted in a better thermal property of prepared co-polymers. The XRD results revealed that higher molecular weight led to a higher proportion of ordered or crosslinking structures in the hybrid resin system. The relationship between the thermal resistance, mechanical properties and the molecular weights of phenolic resins needs further study.

An ultra-low density fiberboard was made of plant fiber using a liquid frothing approach. The inflammability of the plant fiber limited its application as a candidate for building insulation materials and packaging buffering materials. Si-Al compounds were introduced into the foaming system because of the high temperature resistance of Si and Al compounds. The results from energy-dispersive spectroscopy suggested that the Si and Al relatively evenly covered the surface of the fibers, and their weight ratios in the material increased as a function of the amount of Si-Al compounds. The increasing weight ratios of Si and Al affected the fire properties of the material, reducing the released amount of heat, smoke, and off-gases such as CO and CO2, as well as decreasing the mass loss percentage, shown through the use of a Cone Calorimeter. It follows that Si-Al compounds have an evident collaborative effect on the halogen fire retardant. The system can effectively restrain the fire hazard intensity and the yields of solid and gas volatiles.

Ultra-low-density fiberboards (ULDFs) were prepared by a liquid frothing technique using plant fibers as the matrix and Si-Al compounds as the filler to be used as a versatile bio-based composite. Si-Al compounds played an important role in the fire properties of ULDFs. Fire intensity and the amount of volatiles were significantly restrained because of the Si-Al compounds. To determine the combustion mechanism of ULDFs treated by Si-Al compounds, the microstructure of burned specimens was tested by chemical analysis, X-ray diffractometer (XRD), and infrared spectrometer (IR). According to the results from gas chromatography, glucose, xylose, and mannose disappeared in the bottom ashes. After combustion, the XRD profiles of the two ashes became weaker and broader; the sharpest peaks at 18.6o (2) that represented Si-Al compounds remained; the obvious peaks at 22o (2) from cellulose were gone. The results from IR suggested the characteristic functional groups OH, CH, and C=O from carbohydrate also disappeared, and absorbance at 1200 to 400 cm-1, which attributed to the vibration of Si-O, Al-O, and Si- O-Si bonds, increased. In conclusion, fibers are almost completely pyrolyzed at 780 °C. The crystalline structure of Si-Al compounds is rearranged and more amorphous silicon oxide and aluminum oxide are generated.

The synergistic effect of two fire retardants, a Si-Al compound and chlorinated paraffin, was tested on ultra-low density fiberboards (ULDFs). To further understand the mechanism of fire retardancy, morphologies of unburned and burned ULDFs were studied using a scanning electron microscope with energy dispersive spectroscopy. It was found that as the volume of the burned ULDFs shrank, some crevices appeared. In addition, less fly ash formed on the top of specimens, and more bottom ashes remained in the original framework, with a clear network of structure built by the fibers. Carbon was almost absent in the fly ash; however, the weight ratio of C in the bottom ashes reached the maximum (> 43%) of the composition. Oxygen, Al, and Si appeared to have varying weight ratios for different ashes. Oxygen content increased with increasing Si and Al contents. Furthermore, Cl sharply decreased to less than 1% after combustion. Therefore, upon combustion, it was found that almost all of the substances in ULDFs, except for the Si-Al compound, were pyrolyzed to volatile carbon oxides and Cl compounds, especially the fly ash and lightweight C compounds.

There is a growing need for climate-conscious constructions. Exterior walls insulated with straw bales are potentially a step in this direction. The straw is locally produced, carbon neutral, and has good energy efficiency. However, the susceptibility of straw to mold is a major concern in temperate climates. The purpose of this study was to investigate the risk of mold growth in exterior walls insulated with straw bales. Through computer simulations using the software Wärme Und Feuchte Instationär (WUFI), the relative humidity and temperature in vented and unvented exterior straw bale walls were examined under southern Swedish climactic conditions. The relative humidity and temperature were then applied to three different mold models: the Isopleth, the Folos 2D-, and the Mold Resistance Design (MRD) model. A parametric study was also conducted to ascertain the most sensitive parameters for straw bales. One of the primary objectives was to investigate whether there was any construction that had no risk of mold growth. The study showed that the common design solutions for straw bale constructions were likely to incur a risk of mold growth. Ventilated, infrequently used straw bale constructions incurred less risk of mold growth.

Wall heating is an alternative method for residential heating that is used in a limited part of Europe. The goal of this study was to show the feasibility of this method for the Nordic market and to provide a comprehensive picture of wall heating and its functionality compared to traditional methods, i.e. radiators and floor heating. The study was conducted using literature reviews, calculations, and a survey. Simulations were made using the computer software EnergyPlus (US Department of Energy). Results showed that placement of wall heating panels in interior walls results in a lower heat loss than placement in outer walls, and that wall heating can have equal or better energy-efficiency compared to floor heating and conventional radiators. Wall heating provides a more comfortable indoor climate, in regard to dust allergies, and there is no need to remove air from each individual heating panel. A disadvantage is the need for hidden installation, which creates a problem for a safe water installation and difficulties in the attachment of fixtures. Also, the wall heating system has difficultly in handling cold drafts. Though wall heating could compete with floor heating and radiators, its disadvantages are sufficient to explain why the system is not yet used in Sweden.

One of the important Canadian Wood Fibre Centre’s mandates is to develop methods to facilitate the flow of information on the wood quality and quantity along the chain of forest values. Among its research projects, one entitled Enhanced Forest Inventory aims to produce tools to map the wood attributes in terms of physico-mechanical properties by using prediction models based on the attributes of the forest tree and stand. The main inputs of these models come from non-destructive measurements on standing trees (acoustic probe, resistograph, terrestrial lidar) and from spatial data (aerial lidar). Among the obtained results, the correlations are significant between acoustic velocity, drill resistance, tree and stand attributes. These results open the prospect of using the data of non destructive measurements such as acoustic probe and resistograph as complementary input with tree and stand attributes (dbh, crown, and competition index) for prescribing the intensity of thinning to a desired level of wood density.

The block shear strength of Norway spruce (Picea abies (L.) Karst.) glulam joints was tested under low temperatures. Glulam samples were glued with the three of the most common outdoor structural adhesives. The cold temperatures tested were 20, -20, -30, -40, -50, and -60 degrees C. Within the temperature test range, the block shear strength of the glulam joints was resistant to the effect of temperature. As the temperature decreased, the joints' block shear strength did not show any significant change. In most cases, phenol-resorcinol-formaldehyde (PRF) adhesive yielded the strongest block shear strength, while melamine-formaldehyde (MF) adhesive yielded the weakest block shear strength. Melamine-urea-formaldehyde (MUF) adhesive yielded similar results to those of MF adhesives for all temperatures tested. The block shear strengths of the glulam joints with PRF, MUF, and MF adhesives were not sensitive to temperature change. The results indicated that PRF, MUF, and MF adhesives are stable for outdoor structural engineered wood construction in cold climates. The results also suggest that the SS-EN 14080 (2013) standard for the block shear method may not be the proper standard for testing differences in shear strength at different temperatures. The EN 302-1 (2011) standard could be more suitable for this purpose.

This is the second part of a two-part study aimed at examining the effect of extreme adhesive pH on bond durability. The first part dealt with short-term exposure and this second part dealt with long-term exposure. This part also included an examination of wood degradation by adhesive pH.Nine structural wood adhesives [four high pH phenol formaldehyde (PF), one intermediate pH phenol-resorcinol formaldehyde (PRF), two low pH melamine formaldehyde (MF), and two low pH melamine-urea formaldehyde (MUF)] were studied in terms of their pH effect on wood-adhesive bond durability using Douglas-fir wood substrate with specimens tested in block shear. The block shear specimens were initially subjected to vacuum-pressure treatment under water, followed by exposure, while wet, at 50°C for 0, 4, 8, 12, and 17 months. At each exposure period, the specimens were dried to their original moisture content prior to testing for shear strength and evaluation of wood failure.Indications of the extent of degradation of the wood layer adjacent to the bond line due to adhesive pH during the long-term exposure were also examined by the 1% sodium hydroxide solubility test. There were indications that the wood layer closest to the bond line, which contained included glue, had higher solubility compared to those farther from the bond line. This suggests that wood degradation and/or adhesive decomposition occurred and was considered to be induced by the adhesive alkalinity or acidity under the long-term exposure conditions.The PF showed the best durability performance followed, in decreasing order, by PRF and MF/MUF. The latter adhesives degraded completely after an exposure period of 8 to 17 months.The four PF adhesives passed the shear strength and wood failure requirements of the well-known North American structural wood adhesive standards indicating that their high pH had no significant detrimental effect on the wood-adhesive bond durability after the 17-month exposure period despite their being subjected to multiple cyclic tests. This observation was not apparent for the PRF, and the pH effect was considered inconclusive for the MF/MUF since they degraded during the exposure period.The results of this study provide support to wood adhesive standards that do not impose restriction on the upper spectrum of the pH range, and would be useful to adhesive standard developers. These results also serve as background information for adhesive companies in their formulation of wood adhesives as well as for bonded wood product manufacturers in their use of adhesives and for builders in their use of bonded wood products.

As wood construction increasingly uses engineered wood products worldwide, concerns arise about the integrity of the wood and adhesives used. Bondline strength is a crucial issue for engineered wood applications, especially in cold climates. In this study, Norway spruce (Picea abies) joints (150 mm × 20 mm × 10 mm) were bonded with seven commercially available adhesives: polyurethane (PUR), polyvinyl acetate (PVAc), emulsion-polymer-isocyanate (EPI), melamine-formaldehyde (MF), phenol-resorcinol-formaldehyde (PRF), melamine-urea-formaldehyde1 (MUF1), and melamine-urea-formaldehyde2 (MUF2). Each adhesive was tested at six temperatures: 20, −20, −30, −40, −50 and −60 °C. Generally, within the temperature test range, temperature changes significantly affected the shear strength of solid wood and wood joints. As the temperature decreased, the shear strength decreased. PUR adhesive in most cases resulted in the strongest shear strength and MUF adhesive resulted in the weakest. MF and PRF adhesives responded to temperature changes in a similar manner to that of the PUR adhesive. The shear strengths of wood joints with PVAc and EPI adhesives were more sensitive to temperature change. At low temperatures, the variability of shear strengths increased with all adhesives. Percent wood failures of joints bonded with different adhesives in most cases were not sensitive to temperature changes

The impact of cold temperatures on the shear strength of Scots pine (Pinus sylvestris) joints glued with seven commercially available adhesives was studied in this work. The cold temperatures investigated were: 20, −20, −30, −40, and −50 °C. Generally, within the temperature test range, the shear strength of Scots pine solid wood and wood joints were more resistant to the effect of temperature than those of Norway spruce. As the temperature decreased, only some of the joints’ shear strength significantly decreased. In most cases, PUR adhesive yielded the strongest shear strength and MUF adhesive yielded the weakest shear strength. MF adhesive responded to temperature changes in a similar manner to that of PUR and PVAc adhesives. The shear strengths of wood joints with PRF and EPI adhesives were more sensitive to temperature change. For dynamic tests of shear strength, the values for 12-h and 6-day tests under temperature cycles (−20 and 0 °C) were compared. The values for 6-day tests were lower than those for 12-h tests. Therefore, the duration of the samples subjected to the same temperature had a significant impact on shear strength. Our results indicate that PUR adhesive is the most stable; whereas the stability of MUF and PRF adhesives decreased significantly.

As wood constructions increasingly use engineered wood products worldwide, concerns arise about the integrity of the wood and adhesives system. The glueline stability is a crucial issue for engineered wood application, especially under cold climate. In this study, Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) joints (150mm x 20mm x 10mm) were bonded with seven commercially available resins (PUR, PVAc, EPI, MF, MUF1, PRF and MUF2) and tested at six temperatures (20, -20, -30, -40, -50 and -60 °C), respectively. Generally, for both species, temperature changes significantly affected shear strength of wood joints. As temperature decreased, the shear strength decreased. PUR resin resulted in the strongest shear strength at all temperatures tested. MF resin responded to temperature changes in a similar ways as the PUR resin. The shear strength of wood joints with EPI resins was sensitive to temperature change. MUF, PRF and PVAc resins demonstrated different characters with Norway spruce and Scot pine. At room temperature, all types of adhesive showed relative stability, in terms of shear strength variation. While at low temperature, the shear strength varied considerably. More specimens need to be tested in further work to more completely present the issue. The EN 301 and EN 302 may need to be specified based on wood species.

The ability of wood to buffer and mitigate the effects of strongly acidic or alkaline environ- ments produced near the glue line by extreme pH structural adhesives was evaluated. The pH values of wood, cured adhesives, and mixtures of the two in water slurries were determined for different wood types. The pHs of slurries of seven highly alkaline phenol–formaldehyde adhesives were lowered when the adhesive was cured in the presence of wood dust with effects increasing with the proportion of wood in the mixture. The “acidities” or amounts of alkali needed to adjust the slurries to pH 12.5 were relatively high for all species because of weak acid groups in wood that dissociate at pH greater than 8. This explains the ability of wood to buffer highly alkaline adhesives. The pHs of slurries of two acidic melamine–urea–formaldehyde adhesives increased in the presence of wood, but the effect was less significant compared with the alkaline adhesives. Similarly, the “alkalinities” or amounts of acid required to adjust the slurries to pH 3 were relatively low. Aspen veneer samples had a greater effect on adhesive pH than spruce and Douglas-fir. These effects will help mitigate potentially adverse effects of strongly alkaline or acidic adhesives on wood adhesive bond strength.

This study evaluated the fatigue performance of T-shaped, end-to-side, metal-plated joints made of 18-mm (23/32-in) structural oriented strandboard (OSB) to obtain the static-to- fatigue moment capacity ratios. A total of 80 joints with metal plates of different configurations were subjected to one-side cyclic stepped bending loads. Test results showed that assem- blies with OSB metal-plates would fail within 25,000 cycles when a stepped load level exceeded 63 percent of their static moment capacity. The passing static-to-fatigue ratios aver- aged 2.5 with a COV of 22 percent. In all metal-plated joints, the dominating failure mode was metal-plate yield; the rest was shear-out of OSB.

Metal-plate connectors are commonly used to connect critical joints in upholstered furniture frames due to their high load resistance, rapid assembly, and easy connection of members with uniform thickness. To successfully introduce oriented strand- board (OSB) into furniture frames, basic data for metal-plated joints constructed of OSB is needed. In this study, static moment capacity of T-shaped joints with metal-plates was determined experimentally for different configurations. The moment capacity and stiffness of the joint with one pair of metal-plates increased in proportion with the width of the metal-plate up to 6-in (152 mm). When the metal-plate was equal the full width of the OSB member, too many teeth cut into it, making the assembly weaker. Metal-plated joints with two pairs of plates were nearly 50 percent stronger and stiffer than those with a single pair of metal-plates covering the same area.

The main objective of this study was to characterize localized density effects on some common fasteners’ holding capacities in wood-based panels. Oriented strand board (OSB) of three different thicknesses, medium density fiberboard (MDF), and particle board (PB) were tested for screw and staple withdrawal from face and edge, head pull-through, and for screw lateral resistance. The fastener holding capacities were correlated with localized density of the panels. Test results indicated that in the OSB panels, density variation had a significant effect on the screw withdrawal, head pull-through, and lateral resistances, but the effects were less evident for the staple withdrawal and head pull-through. For PB, density variation had a significant effect on the screw withdrawal and head pull-through resistances, but the effects were less pronounced for screw lateral resistance, staple withdrawal and head pull-through. For MDF, no significant correlations were found; this could be attributed to the low density variation in these panels. The data will be used for the optimization of furniture frames, and to provide recommendations to the panel industry on the use of the fasteners with their products.

To improve our understanding of localized density effects in wood-based panels on the holding capacities of fasteners commonly used in furniture, a comprehensive study was conducted using static and cyclic tests of withdrawal and head pull-through of screws and staples and lateral resistance of screws in oriented strandboard (OSB), medium density fiberboard (MDF), and particleboard. In this paper, results of cyclic tests are presented and comparisons are made with the static test results reported in Part 1. Similarly to static tests, cyclic test data indicated that density variation in OSB panels had a significant effect on screw withdrawal, head pull-through, and lateral resistances, but the effects were less evident with staple withdrawal and head pull-through. For particleboard, density variation had a significant effect on screw and staple face withdrawal and head pull-through resistances, but the effects were less pronounced for screw and staple edge withdrawal and screw lateral resis- tances. For MDF, no significant correlations were found, which was likely due to the low density variation in these panels. The data from this study will be useful to the panel industry and furniture manufacturers for optimizing use of panel products and fasteners in furniture frames.

Gusset-plate and metal-plated connectors are commonly used in joints of upholstered furniture frames due to their high load resistance. To successfully introduce oriented strandboard (OSB) into furniture frames, basic data on the performance of the joints constructed of OSB members is needed. In this study, out-of-plane static moment capacity and rotational stiffness of T-shaped joints with gusset-plates and metal-plate connectors (MPC) were determined experimentally for different configura- tions. On average, gusset-plate joints exhibited about 80 percent higher out-of-plane static moment capacity than MPC joints. The rotational stiffness of gusset-plate joints without glue was similar to that of MPC joints; however, the stiffness of glued gusset-plate joints was, on average, 70 percent higher. Among MPC joints tested, those with two pairs of 2- by 6-in metal plates showed the highest unit resistance. For gusset-plate joints, an increase in length of the gusset plate from 4 to 8 inches increased the moment capacity for both glued and unglued joints, but a further increase of the length did not result in any significant increase in the strength. It can be concluded that for the studied joint geometry, the 8-in gusset-plate presented the optimum design. Comparisons with previous in-plane bending tests on the joints of the same type and configurations showed that the in-plane moment capacity was 4 to 6 times higher than that out-of-plane.

Power-driven staples are commonly used to join framing members in upholstered furniture construction because of their quick and easy installation. To successfully introduce oriented strandboard (OSB) into upholstered furniture as frame stock, moment capacity data for stapled gusset-plate joints constructed of OSB are needed. In this study, the static moment capacity of T-shaped, end-to-side joints with two gusset-plates was determined experimentally and analytically for gusset-plates of different lengths (4, 6, 8, 10, and 12 inches) attached with 1.0-inch- and 1.5-inch-long staples with and without adhesive. The moment capacity of the joint increased in proportion with the length of the gusset-plate until the strength of the gusset exceeded that of the main joint member. Analytical prediction of the moment capacity of an unglued stapled joint was found satisfactory. Ap- plication of glue to the connection surface changed the failure modes of the joints and increased their moment resistance capacity.

In order to obtain the ratios of static-to-fatigue moment capacity, the fatigue performance of T-shaped, end-to-side gusset- plate joints made of oriented strandboard (OSB) was investigated. A total of 108 stapled and glued-stapled joints with gusset- plates of different lengths (6, 8, and 10 in) were subjected to one-side cyclic stepped bending loads. Test results showed that assemblies with OSB gusset-plates would fail within 25,000 cycles when a stepped load level exceeded 63 percent of their static moment capacity. The passing static-to-fatigue ratio averaged 2.1 with the COV of 12 percent. In the stapled joints, the higher ratios were associated with the staple withdrawal as dominating failure mode. In the glued-stapled joints, lower ratios were associated with in-plane shear and the higher ratios with the rupture of the OSB panels.

Engineered wood is increasingly used in large structures in Europe, though little is known of its behavior in cold climate. This paper presents the structural health monitoring (SHM) system of a newly built suspension bridge with a deck of glulam timber as well as a bond stability study regarding cold climate performance of engineered wood. The bridge is located in Skellefteå in northern Sweden, and it connects two parts of the city situated on opposite shores of the Skellefteå river. In this ongoing study of the timber-bridge, a structural health monitoring system is employed to verify structural design and long-term performance. This 130m-span bridge is monitored using GNSS receivers, MEMS accelerometers, laser positioning systems, wireless moisture content sensors, strain gauges and weather stations. Data from the monitoring systems is analyzed regarding accuracy, complexity, costs and reliability for long time use. Engineered wood application in bridges, sports centers and timber buildings are discussed. Bond stability of glulam structures in cold climate is also examined in a range of experiments ranging from small glued wood joints to full size glulam bridge performance over time. From an engineered wood material point of view, the study is relevant to cold regions such as Scandinavia, Canada, Alaska, Russia, and the northern parts of China and Japan etc. The engineered wood constructions in these areas will be exposed to low temperature in a quite long period each year. The goal is to determine how engineered wood behaves when exposed to temperatures between 20 °C to -60 °C.

This study is one part of a whole project called "Impact of Extreme pH of Structural Adhesives on Bond Durability." The objective of this study was to evaluate effects of pH on wood-adhesive bond strength and chemical change in aspen (Populus tremuloides Michx) wood caused by extreme pH exposures. Aspen veneer lap-shear samples were tested for maximum stress (N/mm2) and wood failure (%) after exposure to soaking in different buffered solutions (pH = 2.0, 2.5, 3.0; water, 10.0, 11.0, 11.5, 12.0, and 12.5) for 1, 4, and 7 mo. One set of samples stored in laboratory conditions was also tested as a control at each test time. Results indicated that bond strength and wood failure decreased after 4- and 7-mo exposures to acidic conditions but did not change significantly under alkaline exposures. However, the buffered acidic solutions (pH = 2.0 and 3.0) did not cause a measurable chemical change in aspen wood, whereas losses in hemicellulose and lignin were found after aspen wood specimens had been exposed to pH > 11.0 buffered solutions.

Using response surface methodology, the pretreatment conditions of kenaf fibers were optimized to improve the tensile strength of kenaf phloem insulation cotton (KPIC). The effects and interactions of three parameters—sodium hydrate concentration (X1), soaking time (X2), and beating time (X3)—on the tensile strength of the kenaf fibers were investigated. The chemical structure of the specimens was characterized by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Sodium hydrate concentration had the greatest effect on kenaf fibers. The maximum tensile strength of 117.6 N resulted from a sodium hydrate concentration of 4%, soaking time of 50 h, and beating time of 12 min. As shown by FTIR and XRD, optimized pretreatment generated surface functional groups and increased the tensile strength of fibers. In conclusion, the pretreatment of kenaf fiber significantly improves the tensile strength of KPIC and also improves the retention rate of the chemicals used during the preparation of KPIC.