Search

Design for disassembly using deconstructable connections facilitates recycling and reusing of building materials and, therefore, reduces waste management problems at the end of service life. In this regard, a deconstructable timber-concrete composite connector using self-tapping screws has been developed at Aalto University. In the presented research, an experimental investigation was performed to further evaluate the effectiveness of this connector in fabricating deconstructable cross-laminated timber (CLT)-concrete composite floors. For this purpose, several CLT-concrete composite beams were fabricated using 5-layer CLT and low-shrinkage concrete. Each beam contained one row of connectors to represent a strip of a full-scale floor. The vibration performance, bending properties, interface slip, failure modes, and ease of disassembly of the beams were investigated. The results were compared with the ones from a reference group of beams fabricated with regular screws. Overall, the deconstructable beams performed exceptionally well by attaining 98.5% of the average bending stiffness of the regular beams. The load-carrying capacity was also similar but governed by the CLT plate. The vibration characteristics were comparable in both groups. After the bending test, the deconstructable beams were disassembled. Although the beams had been exposed to unproportionally large deformations under the bending load, the disassembly process was performed successfully.

This study simultaneously investigates the impacts of adding aluminum foam and slip velocity on natural convection in a square mini-cavity using a numerical method based on Finite Volume Method with SIMPLE algorithm. In order to model various phenomena in the current study, the impacts of changing parameters such as Rayleigh number, slip factor, and Darcy number studies on streamlines, isotherms, and Nusselt number. Increasing Ra number improves the mixing fluid flow and makes vortexes bigger, leading to enhancing Nu number. Likewise, slip velocity affects the boundary layer and temperature distribution, increasing the portion of convection by around 57% in the best case. Furthermore, adding metal foam has various outcomes depending on Ra and Da numbers. The effect of aluminum foam in higher permeability is better in improving Nu number. Simultaneously adding metal foam with Da = 0.1 and slip velocity (λ = 0.1) in the square mini-cavity increases Nu number by approximately 130%. However, In the absence of slip velocity, Nu number decreases by around 6% at Da = 0.0001. So, it is noteworthy that the permeability of porous media has a critical amount in natural convection to be used positively.

The endeavor toward eco-friendly building materials has led to the development of dowel laminated timber (DLT), a product in which sawn timber boards are laminated using hardwood dowels. D...

Timber-concrete composite (TCC) systems are effective solutions for the construction of new structural floors and the rehabilitation of the existing ones. Nevertheless, the subject of design for disassembly of TCC floors is still an area that requires further research and development. In this paper, the concept of a deconstructable connector using self-tapping screws is presented that is aimed to be used for both prefabrication and cast-in-situ construction of TCC floors. On a total of 61 T-section glulam-concrete composite specimens , the shear properties of the deconstructable connector were evaluated and compared to equivalent permanent connectors. The experimental investigation was performed for single and cross-paired screw arrangements with various insertion angles and two different types of screws. A comprehensive failure analysis was performed and the differences between the developed connector and the permanent ones were described. Overall, the deconstructable connector demonstrated a similar shear behavior to the permanent connectors with only marginally smaller strength and stiffness properties and could therefore be used as an environmentally friendly solution for TCC connections.

Developing higher-value structural products from fast-growing eucalypt plantations - that are currently managed for woodchip production - can create new markets for these plantation resources and ensure a sustainable supply of timber for building construction. In this study, structural nail-laminated timber (NLT) panels with different span lengths were manufactured from a 16-year-old fast-grown Eucalyptus nitens plantation using a lamination system that can maximise the use of lower-grade boards in NLT production. The short-term bending performance in the elastic region and the effects of environmental conditions and structural grade of timber on long-term bending creep deflection of the panels were evaluated. The data analysis revealed that the current visual stress-grading method is incapable of estimating the actual modulus of elasticity (MOE) of the plantation Eucalyptus nitens timber. A linear regression model was proposed using the actual MOE of the boards that can predict the MOE of NLT panels with an average accuracy of 98%. The NLT panels made with higher-grade boards showed 22.4% greater MOE values than the NLT panels made with lower-grade boards. The lamination system used resulted in NLT panels with predictable and customised MOE with a remarkable average coefficient of variance of less than 2.6%. The long-term bending creep deflection of the test panels was significantly affected by daily variations in the relative humidity of the environment and structural grade of the timber used. The results of this study can be used in the development of an appropriate NLT production system from fast-grown plantation eucalypt.

Australia’s hardwood plantation estate is predominantly comprised of Eucalyptus nitens and Eucalyptus globulus, which are mainly being managed to produce woodchips—a low-value commodity export. There is an increasing interest by the timber industry in developing higher-value structural products from the low-grade timber recovered from these plantation resources. In this experimental study, for the first time, the bending performance of nail-laminated timber (NLT) and NLT-concrete composite (NLTC) floor panels constructed of the low-grade, fibre-managed Eucalyptus nitens and Eucalyptus globulus timber was evaluated. The test panels were constructed with various span lengths and cross-sectional configurations and subjected to vibration and four-point bending tests. The results indicated that the modulus of elasticity of the Eucalyptus nitens NLT panels (11,074.6 MPa) was comparable to that of NLT panels made of Eucalyptus globulus (11,203.2 MPa). The modulus of rupture of the Eucalyptus globulus panels was 13.8% higher than that of the Eucalyptus nitens ones. The bending properties of the NLT panels constructed of the two plantation species were superior to those of some commercially important mass laminated timber products reported in the literature. Under the limit state design loads, all the NLT and NLTC panels were still in the linear-elastic range. The fundamental natural vibration frequency values of the test panels were above the recommended minimum range of 8–10 Hz for residential and office floors. The two plantation timber species therefore demonstrated sufficient short-term bending performances to be used in the construction of higher-value structural floor products.

This study evaluated the termite susceptibility of Papua New Guinea (PNG) balsa (Ochroma pyramidale) against Australia's most economically important wood-destroying termite species, Coptotermes acinaciformis. Samples of envelope treated PNG balsa with the insecticide bifenthrin and non-treated balsa, radiata pine (Pinus radiata) sapwood and southern blue gum (Eucalyptus globulus) heartwood were exposed to seven different colonies of C. acinaciformis at a field site in the Northern Territory, Australia. The results indicated that balsa is susceptible to termite attack, with a mean mass loss of 30.9% (range 3.8–99.9%). Mean mass losses for radiata pine and southern blue gum were 90.3 and 98.9% respectively. It was evident that balsa can be successfully protected from termite attack with envelope-treatments of bifenthrin, with the latter proving to be highly efficacious at mass/volume retentions much lower than those specified in AS 1604.1 and typically used in the Australian timber preservation industry.

The main goal of this study was to investigate the visual characteristics, recovery rate, and flexural properties of sawn boards from a fibre-managed plantation Eucalyptus globulus resource as a potential raw material for structural building applications. The impacts of the visual characteristics, strength-reducing features, and variation in basic density and moisture content on the bending modulus of elasticity (MOE) and modulus of rupture (MOR) of the boards were investigated. The reliabilities of different non-destructive methods in predicting MOE and MOR of the boards were evaluated, including log acoustic wave velocity measurement and numerical modellings. The MOE and MOR of the boards were significantly affected by the slope of grain, percentage of clear wood, and total number of knots in the loading zone of the boards. The normal variation in basic density significantly influenced the MOE of the boards while its effect on the MOR was insignificant. The numerical models developed using the artificial neural network (ANN) showed better accuracies in predicting the MOE and MOR of the boards than traditional multi-regression modelling and log acoustic wave velocity measurement. The ANN models developed in this study showed more than 78.5% and 79.9% success in predicting the adjusted MOE and MOR of the boards, respectively.

The aim of this study was to examine the impacts of visual characteristics, strength-reducing features (SRFs), and basic density on the mechanical properties of fibre-managed plantation Eucalypt timber to create effective structural grade groups. It is the intension that the results found in this study can lead to the development of a visual stress grading method for fibre-managed plantation timber in the future and influence the development of new applications for the resource in structural elements for the built environment. The plantation specie investigated in this study was Eucalyptus Nitens–390 sawn timber boards. The most important visual characteristics and SRFs likely to influence the mechanical properties of the boards were visually identified and measured before the boards were divided into designated groups for sampling. The impacts of the visual characteristics, SRFs, and basic density of the boards within each group on modulus of elasticity (MOE) and modulus of rupture (MOR) were determined using four-point bending test. The statistical analyses suggest three structural grade groups can categorise the resource. Strong correlations were found between MOE, MOR, and basic density with the visual characteristics and SRFs of the boards in the three grade groups.

In the current study, the second law of thermodynamics and heat transfer of a power-law hybrid nanofluid in a micro-tube with a variable heat flux on the hot wall, the attendance of two porous disks and the hydrophobic wall under a magnetic field with Finite Volume Method (FVM) has been studied. The non-Newtonian nanofluid has contained water/Al2O3-TiO2 in the volume concentrations of 1.5% and 2% nano-particles. The present study has been investigated in four parts in the range of the Reynolds number (10−100) and the nanoparticles volume concentrations (1.5–2%). The first part has examined the influence of using porous disks in the Darcy number (5 × 10−4–5 × 10−6) on nano-fluid flow, cooling and entropy generation. The results showed that the porous medium improves the mean Nusselt number and decreases and increases thermal entropy generation and frictional entropy generation, respectively. In the second part, the impacts of the thermal conductivity ratio (1–16) of the porous disks were studied. Increasing this parameter caused a slight improvement in the mean Nusselt number in almost all cases and enhancing the thermal entropy generation. In the third part, the influences of the Hartmann number (0−30), which shows the strength of the magnetic field, were investigated. Increasing the magnetic force led to improvements in the mean Nusselt number. It also decremented the thermal entropy generation but increased the generation of frictional entropy and added the term's magnetic entropy. In the fourth part, the effects of the hydrophobic wall in first-order and second-order models, and the slip coefficient (0–0.1) were examined. The results determined that the hydrophobicity of the surfaces and the development of the slip factor in both models improves the mean Nusselt number and decreases in all the parameters of the thermodynamics second law, which were seen more changes in the first-order model.

This study tested the machinability of three major timber species grown in Tasmania, Australia, under different resource management schemes: plantation fiber-managed hardwood (Eucalyptus globulus Labill. and Eucalyptus nitens Maiden) and plantation sawlog-managed softwood (Pinus radiata D. Don). P. radiata was used as a control to identify significant differences in machining fibre-managed plantation timber against sawlog-managed plantation timber with numerically controlled computer technology and manually fed timber production techniques. The potential to fabricate architectural interior products such as moldings with plantation fiber-managed hardwood timber that is high in natural features was the focus of this study. Correlations between wood species, variation in moisture content, and density of individual machinability characteristics were analyzed to determine factors impacting the overall quality of plantation wood machinability. Correlations between species and within species groups from the resulting machinability tests are highlighted and discussed. The results indicate that the machinability of sawlog-managed softwood P. radiata is superior in some circumstances to fiber-managed hardwood E. globulus and E. nitens specimens, according to the American Society for Testing and Materials D1666-11.

The use of fast-growing plantation eucalypt (i.e., pulpwood eucalypt) in the construction of high-value structural products has received special attention from the timber industry in Australia and worldwide. There is still, however, a significant lack of knowledge regarding the physical and mechanical properties of the lumber from such plantation resources as they are mainly being managed to produce woodchips. In this study, the physical and mechanical properties of lumber from a 16-year-old pulpwood Eucalyptus nitens H.Deane &amp, Maiden resource from the northeast of Tasmania, Australia was evaluated. The tests were conducted on 318 small wood samples obtained from different logs harvested from the study site. The tested mechanical properties included bending modulus of elasticity (10,377.7 MPa) and modulus of rupture (53 MPa), shear strength parallel (5.5 MPa) and perpendicular to the grain (8.5 MPa), compressive strength parallel (42.8 MPa) and perpendicular to the grain (4.1 MPa), tensile strength perpendicular to the grain (3.4 MPa), impact bending (23.6 J/cm2), cleavage (1.6 kN) and Janka hardness (23.2 MPa). Simple linear regression models were developed using density and moisture content to predict the mechanical properties. The variations in the moisture content after conventional kiln drying within randomly selected samples in each test treatment were not high enough to significantly influence the mechanical properties. A relatively high variation in the density values was observed that showed significant correlations with the changes in the mechanical properties. The presence of knots increased the shear strength both parallel and perpendicular to the grain and significantly decreased the tensile strength of the lumber. The results of this study created a profile of material properties for the pulpwood E. nitens lumber that can be used for numerical modelling of any potential structural product from such a plantation resource.

The investigation of microfluidics heat transfer in recent years has been of great interest to researchers. In studies to improve the thermal performance of micro-devices, the use of nano-fluids, geometric corrections and other parameters have been investigated. In addition to examining the heat transfer of cooling systems, the research of thermodynamics second-law of these systems has been widely studied in recent years. In this study, thermodynamics second law and heat transfer of non-Newtonian nano-fluid in a micro-channel with distributing variable temperature on the wall, the presence and absence of porous blocks and slip velocity with finite volume method (SIMPLE algorithm) have been investigated. Non-Newtonian nano-fluid contains water-CMC as the basis fluid and volume fraction of 3% and 4% nano-particles of TiO2. The current study is reviewed in two sections in the Reynolds number (10−100) and nano-particles volume fraction (3–4). In the first section, it investigates the influence of slip velocity and compares first and second-order models with different slip factor (0–0.1) on heat transfer, fluid flow, entropy generation and exergy losses. The outcomes present that the slip velocity of the first-order increases the mean Nusselt number in the range of 2.02% to 12.48%, and this range is 1.91% to 7.52% for second-order. Also, the first-order and second-order slip velocities reduce the generation rate of frictional entropy by a maximum of 76.2% and 67.43%, respectively. The rate generation of thermal entropy and exergy losses exhibits variable behaviour with Reynolds number. In the second section, the Darcy number (5 × 10−3–5 × 10−5), porosity (0.75–0.95) and thermal conductivity ratio (1–15) with first-order slip velocity are examined. The Nusselt number increases locally by reducing, reducing and enhancing the Darcy number, porosity and thermal conductivity ratio, respectively. The production rate of frictional entropy also increments by more than 800% with reducing Darcy number and porosity.

We studied the effect of loose tenon dimensions on stress and strain distributions in T-shaped mortise and loose tenon (M&LT) furniture joints under uniaxial bending loads, and determined the effects of loose tenon length (30, 45, 60, and 90 mm) and loose tenon thickness (6 and 8 mm) on bending moment capacity of M&LT joints constructed with polyvinyl acetate (PVAc) adhesive. Stress and strain distributions in joint elements were then estimated for each joint using ANSYS finite element (FE) software. The bending moment capacity of joints increased significantly with thickness and length of the tenon. Based on the FE analysis results, under uniaxial bending, the highest shear stress values were obtained in the middle parts of the tenon, while the highest shear elastic strain values were estimated in glue lines between the tenon surfaces and walls of the mortise. Shear stress and shear elastic strain values in joint elements generally increased with tenon dimensions and corresponding bending moment capacities. There was consistency between predicted maximum shear stress values and failure modes of the joints.

We determined the effects of adhesive type and loose tenon dimensions (length and thickness) on bending strength of T-shaped mortise and loose-tenon joints. Polyvinyl acetate (PVAc) and two-component polyurethane (PU) adhesives were used to construct joint specimens. The bending moment capacity of joints increased significantly with increased length and thickness of the loose tenon. Bending moment capacity of joints constructed with PU adhesive was approximately 13% higher than for joints constructed with PVAc adhesive. We developed a predictive equation as a function of adhesive type and loose tenon dimensions to estimate the strength of the joints constructed of oriental beech (Fagus orientalis L.) under uniaxial bending load.

This investigation was conducted to determine the feasibility of using a two-component polyurethane (PUR) adhesive, with special waterproof properties, in constructing wooden structures. We designed and conducted tests to compare the shear strength and adhesion performance of PUR with polyvinyl acetate (PVAc) adhesive on block-shear specimens constructed of oriental beech (Fagus orientalis L.), fir (Abies alba Mill.), poplar (Populus deltoides Bartr.), white oak (Quercus alba L.), sycamore (Platanus orientalis L.) and white walnut (Juglans cinerea L.). The values of the percentage of wood failure were also determined in specimens constructed with each adhesive. The highest shear strength values of both adhesives were obtained in specimens constructed of beech, while the lowest shear strength values were obtained in fir and poplar specimens. Average shear strength of the PUR adhesive was 16.5% higher than that of the PVAc adhesive. Specimens constructed of fir, poplar and sycamore were characterised by the highest percentages of wood failure, whereas the lowest average percentages of wood failure were obtained in beech and oak specimens. With the exception of oak specimens, there was no statistically significant difference between percentage of wood failure among the PUR and PVAc adhesives. Generally, the PUR adhesive showed an acceptable adhesion performance on wood materials used in our study.

About one million hectares of plantation hardwoods, mostly eucalyptus trees of different sub-species (E. nitens and E. globulus), are annually being managed in Australia, which provides a promising resource of raw materials for fibre industries. However, the timber boards required by the Australian hardwood sector are still being either imported from other countries or harvested from the native forests. There is a need to find a practical way to use the plantation eucalyptus in the Australian timber industry. However, the fibre-managed plantation eucalyptus produces structurally low-grade timber which could not be used as individual boards for structural applications—such as building construction. Unsuitable for appearance applications, the structurally low-grade boards may be suitable for producing innovative high-mass engineered timber products. This editorial will briefly discuss drivers, opportunities, and challenges associated with conducting such a research project.

The main goal of this study was to determine the effect of wood species and loose tenon length on the withdrawal force capacity of mortise and loose tenon (M&LT) T-type furniture joints. The specimens were manufactured from oak (Quercus alba), beech (Fagus orientalis L.), poplar (Populus deltoides), sycamore (Platanus orientalis), fir (Abies alba), and white walnut (Juglans cinerea), and the tenon species selected was oriental beech (Fagus orientalis L.). The length of the tenon was determined on the basis of the length glued into the horizontal member of the joint. The lengths in the present study were 10, 20, and 30 mm. It was found that joints manufactured from beech had the highest withdrawal force capacity; this trait was lowest in joints made from the light wood of poplar and fir. The glued-in length of the tenon exerted a significant influence on the withdrawal force capacity of the joints. The greatest withdrawal force capacity increment of M&LT T-type joints was obtained when the tenon length changed from 10 to 20 mm.

The goal of this study was to introduce a method for estimating stress analysis as an efficient procedure for evaluating the strength of mitered corner joints in furniture structures. Tests were carried out to determine the effects of panel type, distance between the centers of dovetail holes and the edges of joints (10, 20, and 30 mm), and type of dovetail key on the load-carrying capacity of mitered corner joints under a diagonal tension load. Specimens were constructed of overlaid medium-density fiberboard (LamMDF) and particleboard (LamPb) and connected with butterfly and H-shaped dovetail keys. Polyvinyl acetate adhesive was used to assemble the joints. Specimens were tested under diagonal tension loads and the corresponding combined stress analysis was conducted using the following formulas: Total stress at the outer edge, Total stress at the inner edge, where sb is bending stress, sa is axial stress, P is axial failure load, L is half of the span length, and t and b are the thickness and width of the joint members. Test results showed that corner joints constructed of LamMDF were 13% stronger than joints constructed of LamPb. For the specimens constructed of both panel types, a 10-mm distance between the dovetail holes and the edges of joints gave better results than distances of 20 and 30 mm. No significant differences were observed between the 2 types of dovetail keys. Total compression stresses at the outer edge were 2 times greater than the total tension stresses at the inner edge of the joints.