Oriented Strand Board Panels Research Articles

Thermal modification of consolidated oriented strandboards: effects on dimensional stability, mechanical properties, chemical composition and surface color

The objective of this paper was to propose a thermal post-treatment to improve the dimensional stability of oriented strandboard (OSB). Commercial OSB panels were obtained from an industrial batch and thermally treated in a single opening hot-press at two temperature levels (190 and 220 °C) and three duration times (12, 16 and 20 min). Dimensional stability, mechanical properties, chemical composition and surface color were studied. The results pointed-out that the proposed treatment can be applied to significantly improve the OSB dimensional stability by reducing thickness swelling, water absorption, and equilibrium moisture content in comparison to the untreated board. The mechanical properties were partially affected with reduction in modulus of rupture and without any adverse effect on the other properties. Chemical degradation occurred, mainly in relation to hemicelluloses contents, reducing equilibrium moisture content. The board surface became darker and this characteristic was correlated with the observed properties improvement. Dimensional stability properties were affected by both temperature and duration of the treatment, while the others mainly by temperature. The proposed thermal treatment can be recommended as a post-treatment to improve the OSB performance.

Efeito do tratamento térmico sobre a resistência ao cisalhamento da linha de cola em painéis OSB.

As pesquisas sobre o tratamento térmico em painéis OSB (oriented strandboard) vêm buscando reduzir a higroscopicidade dos painéis, bem como aliviar as tensões geradas durante o processo de prensagem. Entretanto, o tratamento térmico acima de 160ºC pode causar inativação da superfície da madeira, tornando-a mais lisa, diminuindo a penetração do adesivo e por conseqüência, reduzindo a qualidade da adesão. O lixamento da superfície de painéis OSB pode tornar a superfície mais rugosa aumentando a qualidade da adesão e a resistência na linha de cola. O presente estudo teve como objetivo avaliar a resistência na linha de cola de painéis OSB tratados termicamente, assim como a influência do lixamento na qualidade da colagem dos painéis. Foram obtidos, aleatoriamente painéis comerciais de OSB que foram tratados termicamente em prensa laboratorial segundo dois níveis temperaturas (190 e 220ºC), três tempos de duração (12, 16 e 20 minutos). Foram cortados 84 corpos-de-prova (CP) sendo que a metade foi lixada. O ensaio de resistência ao cisalhamento da linha de cola foi conduzido segundo ASTM D1037, sendo avaliado o adesivo resorcinol-formaldeído na gramatura de 360 g/m². Os resultados mostraram que o tratamento térmico teve influência na resistência, diminuindo-a levemente em comparação ao material não-tratado. Foi identificado efeito interativo entre a temperatura e o tempo de tratamento. Entretanto, com a operação de lixamento esse efeito foi removido e as diferenças com a testemunha foram diminuídas. Observou-se que os ganhos na resistência com o lixamento foram de até 15%. Sendo assim, o tratamento térmico apresentou pouca influência na resistência da linha de cola e o efeito do lixamento apresentou-se como um processo benéfico, melhorando a qualidade da adesão dos painéis OSB.

Effect of panel properties on the concentrated static load (CSL) performance of oriented strand board (OSB)

The relationship between concentrated static load (CSL) performance of oriented strand board (OSB) and panel thickness, local density, and some mechanical properties (including modulus of elasticity (MOE), modulus of rupture (MOR), and interlaminar shear strength in both major and minor directions) was investigated using both a simple linear regression method and a stepwise multi-linear regression technique. The sample boards were laboratory manufactured OSB panels consisting of eighteen combinations of different strand geometries (length, width, and thickness), strand orientations, and fines contents. Simple linear regression analysis showed that MOE (major direction), MOR (major direction), shear strength (major direction), local thickness, average board density and local density were all significantly and negatively correlated with the CSL deflection; however, in the stepwise multi-linear regression analysis only MOE (major) and local thickness were retained as significant factors possibly due to inter-correlation amongst the variables. Shear strength (major direction), MOR (major direction), average board density, MOE (major direction), MOR (minor direction), local thickness, average board thickness, local density, and shear strength (minor direction) were all found to be significantly and positively correlated with the CSL ultimate load in the simple regression analyses, but only shear strength (major) and local panel thickness were retained in the stepwise multi-linear regression model for the CSL ultimate load.

Effect of mat structure on modulus of elasticity of oriented strandboard

A model to predict bending stiffness of oriented strandboard (OSB) was tested with pilot plant experimental data. The experimental procedure developed in this study is unique in that it allows the model to be tested for extensive vertical configurations of strand angle distribution. After validation, the model was used to simulate a typical three-layer cross-oriented OSB panel with a vertical density profile and strand angle distribution measured on industrial panels. Analysis of the simulated vertical distribution of modulus of elasticity (MOE) indicated that the layers near the panel surfaces contributed much more to the effective parallel panel MOE than those close to the panel thickness center, with 80% of parallel MOE coming from the top 41% of weight and 32% of thickness. The effectiveness of methods to increase parallel bending stiffness through improving mat structure was evaluated. Increasing face/core weight ratio from 54/46 to 66/34 resulted in a 3.7% increase in simulated parallel MOE. Alignment of strands in face layers was identified having a greater potential to increase parallel MOE. Simulations with three improved strand angle distributions showed gains of 5.7, 12.0 and 19.8% in parallel MOE compared with a typical strand angle distribution of industrial OSB panels.

Evaluación de Propiedades Físicas y Mecánicas de Tableros OSB Utilizando Técnica de Ensayo No Destructiva

The efficiency of ultrasound techniques to estimate physical and mechanical parameters of commercial Oriented Strand Board (OSB) panels manufactured in Brazil, has been investigated. Among engineered wood products, the OSB is the one that has been increasingly used in building subsystems, all around the world. Also, nondestructive methods are frequently preferred to be applied to wood based materials. Structural OSB/3 panels were tested, being one 15mm thick and the other 25mm thick. The mean velocity values obtained in panels OSB in longitudinal and transversal directions, as well as the significant linear correlation between some physical and mechanical properties, the velocity and dynamic constants suggest the possibility of using ultrasound techniques in OSB quality control.

Comparison between oriented strand boards and other wood-based panels for the manufacture of furniture

The use of oriented strand boards (OSB) is relatively uncommon in the design of furniture. Yet, their excellent mechanical performance, especially with regard to bending, could make them an ideal material for certain applications. In this study, experiments were carried out to compare OSB panels with other wood-based panels, widely used in the furniture industry, such as medium-density fibreboard and particle boards, as regards to their resistance to bending, the defects that appear as a result of the application of the coating, their economic costs and their aesthetic properties.

Effect of radiata pine juvenile wood on the physical and mechanical properties of oriented strandboard

This work analyzes the impact of radiata pine (Pinus radiata D. Don) juvenile wood on the physical and mechanical properties of oriented strandboards (OSB). Radiata pine logs were obtained from 10 trees of a 26-year old managed stand located in the 8th Region of Chile. The experimental design considered the proportion of juvenile wood and strand orientation as independent variables. OSB panels of 0.4 m×0.4 m×12 mm were produced and tested. The results show that the juvenile wood proportion has a significant impact on the physical and mechanical properties of OSB. Strands orientation had a significant impact on all the properties studied with the exception of the modulus of elasticity in bending. However, this impact was small in all cases and would not change panel grade with the exception of linear expansion. In this case, panels made from tangential strands showed a higher linear expansion. According to these results, radiata pine juvenile wood can be used for the manufacturing of OSB up to a proportion of 70% of the oven-dry wood weight without significant losses of the physical and mechanical properties if the juvenile wood strands are located in the surface layers.

Use of fungal metabolites to protect wood-based panels against mould infection

Wood-based composites such as oriented strand board (OSB) are principle framing elements in building construction in North America. However, these materials are often affected by moulds in wet or humid environmental conditions. A common control method for prevention of mould growth on panels is preservative treatment of panels with various pesticides or chemicals. In recent years, environmentally friendly pest control methods are required because of environmental issue. This research aimed to develop a biological technology to protect OSB against mould infection by post-treatment of panels with natural extracts from fungal antagonists. In this study, the culture metabolites of a fungal antagonist, Phaeotheca dimorphospora DesRochers & Ouellette, were extracted, and the antibiotic activity of the extracts was tested in Petri plates against various moulds and decay fungi. The OSB panels were then dip-treated with the extracts and exposed to a humid environment for mould growth testing in a period of 8 weeks. The results showed that the mycelia growth of all fungi tested (moulds, white-rot and brown-rot fungi) was inhibited by the extracts of P. dimorphospora on agar plates. Panel samples dipped with the fungal extracts in acetone got little mould growth on them, whereas untreated control panels and those samples treated with acetone alone were seriously affected by various moulds.

Empirical Punching Shear Failure Theory for Oriented Strand Boards: Preliminary Study

In characterizing the mechanical properties of oriented strand boards (OSBs), the punching shear capacity is not normally determined. Any attempt at developing a failure theory for punching shear from the planar shear strengths and a hypothetical shear perimeter that is similar to the approach in concrete should be most welcome by OSB designers. Fortunately, the planar shear strengths of OSBs are gradually being documented. The planar shear strengths and the punching shear capacities under a 25-mm-diameter load applicator of six OSB panels with thicknesses ranging from 9 to 18 mm have enabled a preliminary assessment of the optimum position of the hypothetical shear perimeter in an empirical punching shear failure theory for OSB. It is shown that a hypothetical shear perimeter that is a distance equal to the thickness away from the boundary of the loaded area enables the prediction of punching shear capacities that are roughly 75% of the measured punching shear capacity for one panel and within 10% of the measured punching shear capacities for the other five panels. Given that punching shear capacity of OSBs is rarely documented, and subject to future validation by other OSB panels, this empirical failure theory could be potentially useful for estimating the punching shear capacity of oriented strand board.

Performance of Wood Shear Walls Sheathed with FRP-Reinforced OSB Panels

This study addresses the development and structural testing of a hybrid sheathing panel designed to improve the lateral resistance of light wood-frame shear walls. The panel consists of thin outer sheets of oriented-strand board (OSB) bonded to strips of fiber-reinforced polymer (FRP) that are sandwiched between the OSB panels at the edges. The FRP-reinforced panel material selection and fabrication are summarized. Monotonic and cyclic tests were conducted to assess the performance of single-connector sheathing-to-framing connections using both OSB and FRP-reinforced OSB. Twenty-four full-scale shear walls were tested under monotonic and cyclic racking loads to determine the benefits of FRP-reinforced OSB to wall lateral load resistance. For a 102 mm perimeter nail spacing, FRP-reinforced OSB-sheathed walls exhibited increases in peak capacity and energy dissipation under cyclic loading of 27 and 73%, respectively, compared to walls sheathed with conventional OSB. Based on these experimental results, FRP-reinforced OSB panels appear to have significant potential for increasing the energy dissipation capacity and lateral load resistance of wood-frame structures subjected to extreme lateral loads. However, their full utilization will require higher strengths for critical shear wall components such as tension ties and framing interconnections, as well as improvements in sheathing-to-framing fastener performance.

Contact thermal post-treatment of oriented strandboard to improve dimensional stability: A preliminary study

The oriented strandboard (OSB) has less dimensional stability than plywood, but they are competitive panels and have been used for similar ends. The wood-water relation variables, such as thickness swelling and water absorption, express this OSB dimensional instability and can be explained by two main factors: wood hygroscopicity and imposed hot-pressing stresses. The objective of this present paper was to propose a thermal post-treatment as a method to improve OSB dimensional stability by decreasing wood hygroscopicity and releasing hot-pressing stress. OSB panels from Pinus taedawood were produced in laboratory, and their characteristics were: single layer, 0.8 g/cm3; 8% phenolic resin and without wax. The OSB panels were treated in a laboratory press at 250 °C for about 4, 7 and 10 minutes. The wood-water relation variables, thickness swelling (TS), water absorption (WA), equilibrium moisture content (EMC) and springback or permanent thickness swelling (PTS) were determined and compared with untreated panels. The results showed that the proposed thermal treatment was effective to reduce TS, EMC and PTS, but didn’t affect WA which was affected by panel density reduction. The longer the treatment the higher the dimensional stability, and panel weight loss could be used as predictive variable for the efficiency of the treatment.

CREEP BEHAVIOR OF SOLID-SAWN AND WOOD I-JOIST FLOORS

The creep responses of twelve individual I-joists and six wood-framed floor systems were measured for a duration of approximately 120 days. The I-joists and floor systems were divided into two sets, each having six individual I-joists and three floor systems. The study I-joists were fabricated with laminated veneer lumber (LVL) flanges and oriented strand board (OSB) webbing. The floor systems included one floor framed with No. 1 Southern yellow pine floor joists, which served as a control, and two floors constructed with wood I-joists. All floors were sheathed with OSB panels, nailed and glued to the top edges of the joists, and were designed to carry a total dead plus live load of 2.40 kPa (50 psf). A sustained load of 0.96 kPa (20 psf) was applied for the duration of the experiment. Relative humidity and temperature were maintained between 34% and 60% and between 22°C and 26°C (72°F and 79°F), respectively. The overall average creep ratios (total deflection/instantaneous deflection) of the I-joists, I-joist floor systems, and solid-sawn floor systems were 1.66, 1.53, and 1.71, respectively. The creep ratios of the I-joist and solid-sawn floors were not significantly different (p > 0.05). Observed creep ratios of the solid-sawn floors were greater than those reported by prior studies for nailed solid-sawn floors; observed creep ratios for the I-joist floors were lower than those reported by prior research for a similar, but not identical, I-joist floor system.

Bending-Punching Shear Interaction in an Oriented Strand Board

Concentrated load capacities of 18-mm thick one-way simply supported oriented strand board panels together with the mechanical properties of the panels have enabled an assessment of the effect of bending-punching shear interaction on the panel’s concentrated load capacity. Concentrated load capacities of 5.04, 4.44, and 4.29 kN were obtained for 300-, 450-, and 600-mm span panels, respectively. Punching shear capacity of the panels was 6.04 kN. Load capacities based on bending theories of failure were roughly sixty percent of the measured load capacities. An empirical bending-punching shear interaction equation expressed in terms of the bending and planar shear properties and a hypothetical shear perimeter is proposed that enables the load capacities of the panels to be calculated to within roughly 10% of the measured load capacities. Minimal differences between the load capacities of the simply supported and corresponding dowel-fastened panels suggest that the interaction equation is satisfactory for bot...

Image analysis and bending properties of model OSB panels as a function of strand distribution, shape and size

The technique of image analysis has been used to assess the quality of model oriented strand board panels by investigating the relationships between shape and size of strands, the distribution of strands and bending properties. A batch of commercial strands was analysed by image analysis and the distribution of the shape and size of strands was quantified. The strands were categorised into five strand types as a function of size and aspect ratio. In general, strand shapes were observed to be mostly rectangular and there was also a wide variation in strand dimensions in commercial material. Bigger area strands had low aspect ratios and small strands had high aspect ratios. Half of the commercial strands were longer than 100 mm. Model OSB panels were manufactured in the laboratory by hot pressing strand mats formed from each of the five strand types. Strands were laid up by hand into the forming mat and following pressing the orientation and shape of strands was evaluated by image analysis and the panels were tested in a three point bending. Large area (type 3) strands with high aspect ratios produced model panels with optimum strand orientation and mechanical properties. Type 3 panels were also fabricated from strands dropped through a slotted forming device in order to simulate the delivery of strands to the forming line under factory conditions. As the height of strand delivery increased from 0 to 100 to 200 mm the disorientation of strands in the pressed panels progressively increased and as a result mechanical properties in bending were reduced. Image analysis is therefore a powerful tool for evaluating the distribution of commercial strand shapes and the relationship between strand geometry, strand orientation and the mechanical properties of oriented strand board.

Assessment of test-piece size for punching shear capacity of orthotropic panels: Case study of OSB

The punching shear capacity of a wood-based panel is useful in the assessment of its suitability in flooring. A test method for determination of the punching shear capacity of particleboard is given in British Standard BS 5669. The suitability of the span of test piece specified in BS 5669 for punching shear capacity characterisation of oriented strand board (OSB) has been assessed from concentrated load tests of 15 and 18-mm thick OSB panels under 25 and 50-mm diameter load applicators. Elliptical fan-shaped crack envelopes with major axes that were roughly of the same order as the spans of the test pieces characterised the failure of the test pieces under the 25-mm diameter load applicator. However, when the test pieces were loaded via the 50-mm diameter load applicator, the spans of the test pieces appeared too small to simulate the characteristic elliptical crack envelope. An expression for the test-piece span for characterisation of punching shear capacities under both 25 and 50-mm diameter load applicators has been proposed. The proposed expression is a useful starting point in the determination of suitable test-piece span for punching shear capacity characterisation of OSB.

Failure modes and trend curves for load capacity and stiffness of OSB panels subjected to concentrated load

The determination of the concentrated load performance of floor panels from concentrated load tests is useful in their load capacity and stiffness ratings by floor-panel manufacturers. Concentrated load tests of 18-mm thick one-way spanning simply supported oriented strand board (OSB) panels with ratios of span to thickness of 16.7, 25.0 and 33.3 have been carried out in order to characterise the trends in the stiffness, load capacity and type of failure of the panels. The panels exhibited punching shear-type failures. Linear equations have been fitted to the graphs of stiffness versus ratio of thickness to span squared and to the load capacity versus ratio of thickness to span. Linear relationships between stiffness versus ratio of thickness to span squared and load capacity versus ratio of thickness to span are predicted for continuous and fixed-edge panels. In the light of the extensive use of computerised design programmes and the preference for formulae in new design Standards and Codes, the determination and publication of these concentrated load capacity and stiffness formulae for floor panels should be invaluable to designers.

Timber shear walls with large openings: experimental and numerical prediction of the structural behaviour

A numerical model based on the finite element method is presented for prediction of the cyclic response of wood frame structures. The model predicts the cyclic response of shear walls. Nonlinear phenomena are assumed to be concentrated in the connections that are modelled through elements linking the structural elements including the posts, beams, and sheathing panels. Identification of model parameters relies on tests on individual connections. Connection tests on different nail lengths were conducted under monotonic and cyclic lateral loads. Based on the results from past studies that indicate the pull-through failure is an important failure mode in common nail connections with lumber and oriented strand board (OSB), washers were considered as a means to reinforce the connection. The influence of reinforced nailing on the static and dynamic performance of full-size wood frame shear walls with large openings, sheathed with OSB panels, was evaluated experimentally. Combinations of parameters were studied, such as the number of hold-downs, the panel shapes, the nail distribution, and the bracing systems. Comparisons of the dissipated energy per cycle revealed a higher capacity for walls using nails with washer reinforcement than without. Results from numerical simulations of the monotonic and cyclic tests performed on the walls are presented.Key words: timber shear wall, connections, finite element, dissipated energy.

Capacity of Oriented Strand Board Shear Walls with Overdriven Sheathing Nails

Eight shear wall specimens sheathed with 11 mm structural oriented strand board panels were assembled with overdriven sheathing nails and tested using a pseudo-dynamic procedure. Specimens used 38389 mm Douglas Fir-Larch framing members and 8d cooler, gun-driven sheathing nails. Four overdriven nail depths were considered: flush, 1.6, 3.2, and 4.8 mm. Nails were spaced at 76 mm on center along the edges and 305 mm on center along intermediate supports. Edge nailing distance was 9.5 mm. Two specimens were constructed for each aforementioned overdriven depth. To determine a lower bound on capacity, 100% of the sheathing nails in a specimen were driven to the specified depth. Results from this study indicate that any level of sheathing-nail overdrive will reduce the capacity of a shear wall. Compared to specimens with flush-driven nails, specimens with nails overdriven 1.6 mm suffered 5% loss in strength and gained 1% in displacement capacity. Specimens with nails overdriven 3.2 mm had strength and displacement capacity reduced by 12 and 22%, respectively. Specimens with nails overdriven 4.8 mm fared poorly; strength was reduced 24%, and displacement capacity was reduced 56%.

Monitoring fiber orientation in OSB during production using filtered image analysis

The orientation of oriented strand board (OSB) mats has been practically measured on a commercial factory production line to demonstrate the practical capabilities of the filtered image analysis (FIA) technique. Samples have been cut from OSB panels at a range of angles to the panel axis and these samples have been tested in bending. The factory data and the experimental data have been compared in order to investigate the relationship between the practical condition of fiber orientation in the factory and the bending properties as a function of orientation. The following conclusions can be drawn. Fiber orientation in the production line is good and stable irrespective of position across the width of the production line, time of day and changing line speed. The average value for the orientation angle of the forming mat on the production line is approximately 25°. The general shape of the fiber orientation distribution is similar to a normal distribution, however, at the centre of the fiber mat the sharpness of the distribution is greater than a normal distribution. The average orientations of fibers in commercial board lie at 25° and 60° to the longitudinal and perpendicular directions, respectively. The results suggest that there is potential to improve the mean fiber orientation angle of commercial OSB to improve longitudinal values of MOR and MOE, especially where perpendicular properties are not critical.

Evaluation of the arrangement of wood strands at the surface of OSB by image analysis

The objective of this paper is to evaluate the arrangement of wood strands at the surface of oriented strand board (OSB) by image analysis. Two-dimensional image analysis enables the number of strands and the area of each strand to be computed. In addition, the fiber direction of each strand may be measured manually by recording the acute angle between the fiber direction and the longitudinal axis of the specimen. The image analysis results suggest the following: the average strand area is proportional to the reciprocal of the number of strands. Samples containing many smaller strands exhibit a larger variation in strand size. The average strand area does not correlate with the distribution of the strand area represented by the coefficient of variation. However, there is a reasonable correlation between the number of smaller strands in the range 0 to 1 cm2 and the coefficient of variation of strand area. At low average fiber orientations, i.e. better orientation with the principal panel axis, there is smaller variability in orientation. The upper side and lower side of OSB exhibit a different relationship between average fiber orientation and strand area. The upper side of the specimens contains larger strands and exhibits better fiber orientation than the lower side. This is thought to be a function of the production process. The lower side strands fall on a smooth moving substrate, whereas the upper side strands fall on a stable substrate of strands. The number of strands is lower on the upper side of the OSB panel because small size strands tend to migrate to the lower side of the OSB during production. The small particles tend to be vibrated through the strand mat to the lower face before pressing.