Laminated Veneer Lumber Research Articles

Fiber bundle recombination and gradient uniform lamination to process high-strength and tough bamboo engineering materials

In addition to high strength and stiffness, advanced structural engineering materials and components should also have designability and structural stability. Green building structural materials developed using bamboo face challenges in terms of durability and stability. In this work, we utilize fiber reorganization and gradient uniform lamination a high-strength, high-toughness, uniform and durable outdoor bamboo engineering material- Bamboo Bundle Laminated Veneer Lumber（BLVL) was prepared by the method of. The unique interlayer tight laminated interlocking occlusal structure and the glue nails enhance the interface bonding performance enhanced BLVL performance. The BLVL specific strength, specific modulus, and impact toughness were 267.70 MPa cm3 g−1, 20.73 GPa cm3 g−1, and 13.8 J/cm2, respectively. The density uniformity and dimensional stability were 2.47 and 2.24 times higher than those of the bamboo scrimber (BS), respectively. This work demonstrates the potential to produce lightweight durable structural engineering materials with controllable properties and designable structures from abundant sustainable fast-growing bamboos.

Wood and wood-jute laminates manufactured by vacuum infusion

Unidirectional (called laminated veneer lumber - LVL), which could be applied for structural purposes depending on the adhesive properties. However, these laminates have numerous limitations due to both physical, mechanical and interfacial properties. Thus, this study addresses the vacuum infusion processing of wood and wood-jute laminates and their characterization. Balsa wood veneers, jute fabrics, and a polyester resin were employed in the bicomponent and hybrid laminates with up to nine layers. The analyses were density, water absorption, and tensile, compressive, flexural and short beam testing. The bicomponent (wood/polyester) laminates presented poor mechanical performance due to the insufficient resin impregnation as noticed from the morphology analysis. However, the insertion of intermediate jute fabrics increased density (70–75%), short beam strength (62–67%), flexural modulus (51–116%) and strength (49–82%), tensile modulus (67–78%) and strength (19–47%), which were ascribed to the higher amount of impregnated resin among the jute layers. Also, the higher the number of layers, the poorer the interlaminar properties, especially for the bicomponent wooden laminates.

Experimental study on the vibration of poplar LVL orthogonal ribbed box floor

In this paper, a new type of Popular Laminated Veneer Lumber (LVL) orthogonal ribbed box floor is proposed. Six full-scale specimens of box-shaped floors were tested using the natural excitation method and the human induced excitation method in order to examine the dynamic characteristics and vibration response. The results indicate that the box-type floor specimens with the thickness of the cladding plate, the height of the rib beam, and the distance between the short rib beams of 18.3, 285, and 600 mm exhibit the largest fundamental natural vibration frequency and damping ratio, as well as the best dynamic characteristics. With increasing cladding panels and higher rib beams, peak acceleration decreases, whereas it increases with increasing thickness and shorter rib spacing. The peak acceleration of the floor gradually increases as stride frequency and walking number increase. With the same stride frequency, the peak acceleration of the floor when a single person jumps is greater than when stepping or walking continuously. Combined with related specifications, the root mean square acceleration, peak acceleration, and acceleration vibration level were used to evaluate the vibration comfort of the floors. The methods are presented to predict the fundamental natural frequency and the peak acceleration of the Popular LVL orthogonal ribbed box floor under single walking or jumping conditions, and the predicted results agree well with the experimental results. The research results provide designers with theoretical support for solving the vibration comfort problem on wooden floors.

Economic and environmental life cycle perspectives on two engineered wood products: comparison of LVL and GLT construction materials.

The embodied carbon of building materials and the energy consumed during construction have a significant impact on the environmental credentials of buildings. The structural systems of a building present opportunities to reduce environmental emissions and energy. In this regard, mass timber materials have considerable potential as sustainable materials over other alternatives such as steel and concrete. The aim of this investigation was to compare the environment impact, energy consumption, and life cycle cost (LCC) of different wood-based materials in identical single-story residential buildings. The materials compared are laminated veneer lumber (LVL) and glued laminated timber (GLT). GLT has less global warming potential (GWP), ozone layer depletion (OLD), and land use (LU), respectively, by 29%, 37%, and 35% than LVL. Conversely, LVL generally has lower terrestrial acidification potential (TAP), human toxicity potential (HTP), and fossil depletion potential (FDP), respectively, by 30%, 17%, and 27%. The comparative outcomes revealed that using LVL reduces embodied energy by 41%. To identify which of these materials is the best alternative, various environmental categories, embodied energy, and cost criteria require further analysis. Therefore, the multi-criteria decision-making (MCDM) method has been applied to enable robust decision-making. The outcome showed that LVL manufacturing using softwood presents the most sustainable choice. These research findings contribute to the body of knowledge about the use of mass timber in construction.

Impact of Facility Location on the Financial Performance of Integrated and Distributed LVL Production in Subtropical Eastern Australia

In subtropical eastern Australia, the declining availability of traditional, large hardwood native forest logs has motivated hardwood sawmills to explore potentially utilising small logs in the manufacture of veneer-based engineered wood products (EWPs), such as laminated veneer lumber (LVL). An aspatial mathematical model that maximises net present value (NPV) over a 30-year project life has been applied to estimate the financial performance of LVL manufacture in this region. Of particular interest was how facility location affected financial performance, and whether distributed production of veneer (close to the log resource) and LVL (distant from the log resource) may be more profitable than integrated production under some circumstances. While integrated production of veneer and LVL near the resource maximised NPV, distributed production was found to be more profitable than integrated production in situations where the LVL manufacturing facility had to be located relatively far from the resource. Nevertheless, the level of value-adding and processing scale had a greater impact on financial performance than facility location. The analysis also highlighted that log procurement strategy substantially affected financial performance. Encouragingly for forest growers and wood processors, utilising large volumes of small diameter logs, was important for maximisation of NPV of larger-scale LVL facilities.

Mechanical performance of poplar laminated veneer lumber truss joints

ABSTRACT Poplar laminated veneer lumber (LVL) offers many advantages such as high strength and small variability. This study explored the application of poplar LVL for making light timber trusses in China. A total of 12 poplar LVL truss joint specimens were designed and constructed, including truss support joints and ridge joints connected by bolts and tooth plates. The mechanical properties of the poplar LVL truss joints were experimentally tested and theoretically calculated. It was found that (1) the average bearing capacity of 10-mm bolted joints was 12.98%–22.62% higher than that of 8- or 12-mm bolted ones; (2) the average bearing capacity of ridge joints with 133 mm × 75 mm tooth plates was 23.03% and 28.22% higher than those with 152 mm × 75 mm and 152 mm × 50 mm tooth-plate connected ones; (3) the average bearing capacity of the bolted joints was higher than that of the tooth-plate connected ones when the shape of both joints were the same; (4) The damage of LVL dowel grooves and pull-out of tooth-plates from LVL were observed in the bolted and tooth-plate connected joints, respectively; and (5) The calculated values were, in comparation with the experimental results, were conservative for bolted joints and were in good agreement with the tooth-plate connected ones.

Experimental study of the behavior of box floor with orthogonal ribbed beams by poplar LVL

Considering the unidirectional layout of ribbed beams and simple structure in traditional wooden floors, it is not suitable for large-span wooden buildings. Six groups of floor ribbed beams with plane size of 4.8 m×3.6 m were designed and manufactured by using poplar laminated veneer lumber (LVL), among which five floor specimens were orthogonal ribbed beams and the other one was traditional. A bending performance test was carried out to analyze the influence of different ribbed beam spacing and high span ratio on the mechanical performance of poplar LVL orthogonal ribbed beams, and its results were compared with that of the traditional floor with ribbed beams. The results showed that the box floors with orthogonal ribbed beams had good integrity during the bending process. Moreover, the change of the high span ratio had an important influence on the bending performance of the box floors with orthogonal ribbed beams, and the change of the spacing of the ribbed beams had a relatively small influence on the flexural performance of the box floors with orthogonal ribbed beams. Under the same conditions, the bending performance of the box floors with orthogonal ribbed beams was better than that of traditional floor.

KIZILAĞAÇ VE KAVAKTAN ÜRETİLEN TABAKALI KAPLAMA KERESTELERİN MEKANİK VE FİZİKSEL ÖZELLİKLERİ ÜZERİNE TABAKA KOMBİNASYONUNUN ETKİSİ

Laminated veneer lumber (LVL) is an engineering product material used as girders, beams, joist, headers, panels, etc. in construction. In this study, the effect of ply combination on oven-dry specific gravity, equilibrium moisture content, thickness swelling and water absorption, tensile-shear strength, modulus of rupture, modulus of elasticity and compression strength parallel to grain of LVL manufactured from alder and poplar was investigated. Alder veneer, poplar veneer and urea formaldehyde glue were used in LVL production. LVLs were produced in a total of 10 different combinations. Oven-dry specific gravity, equilibrium moisture content, thickness swelling and water absorption, tensile-shear strength, modulus of rupture, modulus of elasticity and compression strength parallel to grain of test samples were determined according to TS 2472, TS 2471, TS EN 317, EN 314-1, TS 2474 and TS 2595, respectively. Based on this study, the highest modulus of rupture, modulus of elasticity, compression strength and oven dry specific gravity values were obtained with alder veneers used in all plies. On the other hand, the highest tensile-shear strength values were obtained with poplar veneers used in all plies. With the rising in the use of poplar veneer in LVL production, an increase in the amount of thickness swelling and water absorption was observed. It was also observed that as contribution rate of alder veneer in lamination increases, oven dry specific gravity, modulus of rupture, modulus of elasticity and compression strength values were increased.

Monotonic and cyclic pull-pull tests on dowel-nut connector in laminated veneer lumber made of European beech wood

The findings from tests on steel dowel-nut connector in Laminated Veneer Lumber (LVL) bar are reported. Test specimens were prepared using LVL members made of European beech wood (Fagus sylvatica L.), showing a square cross-section of side length 50 mm and veneers arrangement comprised of 18 layers with the grain oriented in the bar longitudinal direction. The tested connection consisted in a 12 mm-diameter longitudinal threaded rod of class 12.9 steel (nominal yield strength fyb = 1080 MPa) screwed into a transverse 20 mm-diameter (=d), 50 mm-long dowel-nut. Three monotonic compression tests and 42 pull-pull tests were carried out. Among these latter, 22 were monotonic and the remaining 20 were cyclic. The dowel-nuts were also made of class 12.9 steel, with the exception of those used in ten cyclic tests, which were of grade S355 steel (fyk = 355 MPa).Preloading the connection with a controlled tightening increased both tension and compression stiffness. Greater tensile strength and smaller results scatter were found for dowel-nut axis orthogonal to the veneers. Load-carrying capacities obtained for dowel-nut end distances of 2.5d and 5d were 33% and 100%, respectively, those obtained for 7.5d. In cyclic tests, no significant increase in the strength degradation was observed due to cyclic loading. In the case of grade S355 dowel-nut, evident plastic deformations were achieved in the connector for end distances 5d and 7.5d. However, this did not influence neither strength nor corresponding displacement.

Design and manufacture of laminated veneer lumber packaging boxes and pallets and evaluation of their mechanical properties

Wooden packaging boxes and pallets are used in a wide range of applications. In this work, LVL from the same source and batch were used as the base material. After dynamic detection and grading, they were divided into two grades (A and B), according to their differences in elastic modulus. The packaging boxes and pallets of the same specifications were designed and manufactured as the research objects. Four mechanical properties studies and related analyses were performed. The three mechanical tests showed different deflection values of the two packaging boxes A and B, and the maximum error was 6.93%. In the rotational edge drop test, the edges of the nether end rails of the two grades of LVL boxes were damaged to varying degrees. Additionally, the nails at the connection between the middle longitudinal beam and the bottom plate also appeared to be pulled out, and the parts made of B-grade LVL were more obvious. The results show that the dynamic detection and quality grading for LVL can effectively distinguish the material grade. The grading results were consistent with the mechanical properties of the LVL packaging boxes and pallets of corresponding grades, which are suitable for use in production lines.

Application of holistic and integrated LCSA: Case study on laminated veneer lumber production in Central Germany

PurposeWe have to transform our societies and economic systems towards social, ecological, and economic (holistic) sustainability. Bioeconomy (BE) can contribute to sustainable development by substituting fossil-based products with renewable ones; however, sustainability is not intrinsic to BE.MethodsTherefore, we developed a holistic and integrated life cycle sustainability assessment (HILCSA) method containing 91 indicators, implemented in openLCA, using the Ecoinvent and SoCa database, and addressing 15 out of 17 Sustainable Development Goals. We applied it for the first time to show its capabilities by assessing the holistic sustainability of laminated veneer lumber (LVL) relative to hot-rolled steel beams.Results, discussionOur results indicate that renewable bio-based construction materials can have a better holistic sustainability than fossil-based products for nearly all indicators, by less stressing the environment, having a less negative impact on society and being economically more efficient. However, fossil-based components of LVL such as phenolic resin are main contributors of negative impacts and should be reduced and replaced. Renewable resources from agriculture and forestry have significant impacts on land use (change).ConclusionsHILCSA demonstrates to be able to provide comprehensive sustainability assessments as well as aggregated results. BE substitutes indeed can improve sustainability; however, sustainability assessments and HILCSA need to be further developed to allow conclusions to be drawn about absolute sustainability of BE.

Nonlinear Finite Element Analysis of Flexural Laminated Veneer Lumber (LVL) Sengon Slender Beam

Laminated Veneer Lumber (LVL) is one of the engineered wood products consisting of wood veneers that are glued and pressed together. In this study, the behavior of LVL Sengon slender beam is numerically investigated by means of nonlinear finite element analysis (FEA), where only half of the experimental beam was modeled due to symmetry of the load configuration. The LVL Sengon wood material used Hill failure criterion with isotropic hardening rules, and its mechanical properties in both tension and compression are modelled according to its mechanical properties in tension obtained from the clear specimen test. The contact analysis is defined for each contacting and contacted elements. The FEA results well agreed with the experimental results in term of the load-deflection curve and failure mode of the beam. It is found that the lateral support has no effect on the stiffness of the beam. The beam stiffness and ultimate load increase by the increase of beam height-to-width ratio (𝑑/𝑏).

Design considerations for robotically assembled through-tenon timber joints

This research investigates the robotic assembly of timber structures connected by wood–wood connections. As the digitization of the timber construction sector progresses, digital tools, such as industrial robotic arms and Computer Numerical Control machines, are becoming increasingly accessible. The new-found ease with which wood can be processed stimulates a renewed interest in traditional joinery, where pieces are simply interlocked instead of being connected by additional metallic parts. Previous research established a computational workflow for the robotic assembly of timber plate structures connected by wood–wood connections. This paper focuses on determining the physical conditions that allow inserting through-tenon joints with a robot. The main challenge lies in minimizing the clearance between the tenon and the mortise in order to keep the connections as tight as possible. An experimental protocol has, therefore, been developed to quantitatively assess the performance of the insertion according to different geometric parameters. Robotic insertion tests have been carried out on over 50 samples of 39 mm Laminated Veneer Lumber. Results showed the interest of tapering the joint with a 5 degrees angle, in addition to introducing an offset of 0.05 mm, to minimize friction forces during the insertion. This configuration was confirmed by successfully assembling a 2,50 m long box girder with the same parameters.

Bonding performance of hot-bonded acetylated beech (Fagus sylvatica L.) laminated veneer lumber (LVL)

ABSTRACT This study demonstrates acetylation with acetic anhydride, one of the few industrial wood modification techniques on the market, to increase the dimensional stability and durability of laminated veneer lumber (LVL) made from beech wood (Fagus sylvatica L.). After being acetylated, veneers were hot-bonded to LVL using phenol-formaldehyde resin (PF) or phenol-resorcinol-formaldehyde resin (PRF). The bonding performance (bonding shear strength (BSS) and wood failure (WF)) was tested under the following three conditions: 20°C and 65% RH, water immersion, and rigorous boiling-drying-boiling cycle. Additionally, using the same specimen sizes on a second sample set, the moisture content (MC) and dimensional stability were determined. Results indicate that the PRF resin provided the strongest bonding performance on acetylated LVL and references. Acetylated LVL had higher BSS in wet conditions than untreated controls, especially after boiling in water, which could be attributed to less wood-water interaction at the cell wall level after acetylation.

Strengthening of Full-Scale Laminated Veneer Lumber Beams with CFRP Sheets.

This paper presents the results of experimental research on full-size laminated veneer lumber (LVL) beams unreinforced and reinforced with CFRP sheets. The nominal dimensions of the tested beams were 45 mm × 200 mm × 3400 mm. The beams were reinforced using the so-called U-type reinforcement in three configurations, differing from each other in the thickness of the reinforcement and the side surface coverage. An epoxy resin adhesive was used to bond all the components together. A four-point static bending test was performed according to the guidelines in the relevant European standards. The effectiveness of the reinforcement increased with the level of coverage of the side surface and the level of reinforcement. The average increases of bending resistance were 42%, 51% and 58% for configurations B, C and D, respectively. The average value of bending stiffness increased for the beams of series B, C and D by 15%, 31% and 43%, respectively. Their failure mode changed from brittle fracture initiated in the tensile zone for unreinforced beams to more ductile fracture, initiated in the compression zone. The influence of the coverage of the side surface by the CFRP sheet and reinforcement ratio on the mechanism of failure and effectiveness of strengthening was studied in the article.

Creep behavior of orthogonal rib box floor of poplar laminated veneer lumber

Poplar laminated veneer lumber (LVL) orthogonal rib box floor is a new type of floor composed of orthogonal LVL rib beams and oriented strand board (OSB). To study the creep performance of the box floor, four 3600 mm × 4800 mm floor specimens were designed and manufactured. The creep tests of the box floor with local damage, repeated load, and different stress ratio loads were conducted. The creep of the floor increased with ambient temperature and humidity. Because of the local damage of the box floor, the creep increased. Repeated loading increased the creep deformation of the floor, and increasing the load accelerated the creep of the floor. Combined with the creep mechanism of wood materials, a creep theoretical calculation formula of the box floor with LVL orthogonal ribs was established. Comparing the creep model analysis with the test data, it was found that the modified Burger mode can well simulate the creep performance of LVL box floor. Therefore, the modified Burger model can be used to calculate the creep deformation of the box floor.

Experimental study on flexural behavior of box floors with orthogonal rib beams made of poplar laminated veneer lumber

This study examined the flexural behavior of the poplar laminated veneer lumber (LVL) box floor with orthogonal rib beams. Four 3.6 m × 4.8 m box floor samples made of poplar LVL orthogonal rib beams and oriented strand board (OSB) plates were tested under vertical uniform loading, from which the bearing capacity, stiffness, and failure characteristics were analyzed. There was no damage in all box floor samples at the normal service load of 2.5 kN/m2, and the maximum deflection was far less than the allowable value. When the maximum load was applied, the load-displacement curve of each floor sample exhibited a linear relationship without obvious failure. However, localized failure was manifested as the dislocation slip of the rib beams relative to the upper and lower floor slabs at the corner nodes and the joint expansion and staggered floors at the bottom plate, with obvious failure signs. The rib beam height had the most significant impact on the floor stiffness, followed by the spacing of short-side rib beams, whereas the OSB plate thickness had lest impact. The mid-span deflections of poplar LVL orthogonal ribbed box floor samples, which were calculated using the analog slab method, were in good agreement with the experimental results with an error being less than 10%.

Durability-related performance of reinforced bondline by phenol formaldehyde/nano SiO2 composite in Laminated Veneer Lumber (LVL)

The development of bonding performance and cohesion of the constituent members is of great interest in the wood-based composites production process. This work presents an investigation for assessment of bondline in reinforced laminated veneer lumber. Phenol-formaldehyde was modified with silicon dioxide nanoparticles (SiO2-NPs), before applying as the binder. Experimentally, the bonding quality and durability were investigated based on penetration parameters, shear strength, apparent cohesive wood failure, and delamination ratio. Results verified that SiO2-NPs had catalytic impacts on the polymerization mechanism of phenol-formaldehyde resin. Bondline morphology was affected by SiO2-NPs presence, in a way that the penetration parameters were reduced under the influence of the viscosity rising and polymerization behavior of phenol-formaldehyde/nano SiO2 composite. With the shorter hot-pressing time, the brittle resin failed cohesively in the bondline, while the reinforced bondline by phenol-formaldehyde/nano SiO2 composite failed by delamination in the wood fibers. The highest shear strength in the core layer was recorded when 2% SiO2-NPs were presented in the bondline. The optimum shear strength and delamination ratio were observed at ≈ 135 and 330 μm penetration depth for effective penetration and maximum penetration, respectively. The SiO2-NPs promoted the bonding durability performance of the bondline, especially in the core layer of the laminated veneer lumbers with shortened hot-pressing time. This reinforced product indicated applicability of being used as a building material in high humid/exterior conditions.

Experimental Investigation on Bending Behavior of Innovative Poplar LVL Floor Diaphragms

Poplar laminated veneer lumber (poplar LVL) is made of fast-growing poplar veneer and structural adhesive, which owns the advantages of sustainability and stable quality. Here an innovative poplar LVL floor diaphragm is presented, mainly made up of orthogonal rib beams fitted together using L-shape steel connectors. The paper mainly deals with an experimental study on the bending behavior of the floor under transverse uniform load. Full-scale testing on eight 3.6 m × 4.8 m specimens shows that the damage phenomena of the floor mainly exhibited as the separation between the rib beams and pulling out from the rib beam for the tapping screw. Though some local damage phenomena appeared before the preset maximum loading level, the load-deflection curves basically kept linear for most of the specimens. Under the service load level of 2.5 kN/m2, the distribution of deflection and strain for the full-length rib beam substantially exhibited the characteristic of a two-way slab. In contrast, for the segmented rib beam, the situation was much more complex. Due to the parametric design of the specimens, testing results illustrated that the rib beam height played the most important role in floor stiffness. Next was the sheathing panel, while the role of segmented rib beam spacing was relatively unremarkable. At last, a revised pseudo-plate method was proposed to evaluate the maximum deflection of the novel floor, which considered the composite action by rigidity factors.

The effects of using different adhesive on the thickness swelling ratio of LVL produced from scotch pine

Most wood properties are affected by changes in moisture content below the wood fiber saturation point. In this study, the thickness swelling ratios of laminated veneer lumber (LVL) produced from Scotch pine (Pinus sylvestris L.) bonded by using polyvinyl acetate (PVAc), polymeric diphenyl methane diisocyanate (pMDI), and a mixture of them were evaluated. Thickness swelling of the samples was calculated after different waiting times under water. While the lowest thickness swelling ratio (1.65%) was determined from bonding with PVAc 92%- pMDI 8%, for 2 hours, the highest thickness swelling ratio (6.35%) was observed from bonding with PVAc 98%- pMDI 2% adhesive for 96 hours. As a result, adding pMDI to the PVAc adhesive reduced the rate of swelling of the test specimens. For this reason, the material can be used potentially in wet or humid places.