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20 records – page 1 of 2.

Cyclic Load Behaviour of Beam-to-Column Glulam Joints Combining Glued-in Rods with Steel Brackets

https://research.thinkwood.com/en/permalink/catalogue2028
Year of Publication
2018
Topic
Connections
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)

Ductility of Dowelled New Zealand Douglas-Fir CLT Connections Under Monotonic and Cyclic Loading

https://research.thinkwood.com/en/permalink/catalogue2114
Year of Publication
2019
Topic
Connections
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Author
Ottenhaus, Lisa-Mareike
Li, Minghao
Brown, J.
Ravn, C.
Scott, B.
Organization
University of Canterbury
Year of Publication
2019
Country of Publication
New Zealand
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Topic
Connections
Keywords
Multi-Story
Douglas-Fir
Dowel-Type Connections
Dowels
Language
English
Conference
Pacific Conference on Earthquake Engineering
Research Status
Complete
Online Access
Free
Resource Link
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Durability of Structural Lumber Products after Exposure at 82C and 80% Relative Humidity

https://research.thinkwood.com/en/permalink/catalogue784
Year of Publication
2005
Topic
Mechanical Properties
Moisture
Material
LSL (Laminated Strand Lumber)
LVL (Laminated Veneer Lumber)
Solid-sawn Heavy Timber
Author
Green, David
Evans, James
Hatfield, Cherilyn
Byrd, Pamela
Organization
Forest Products Laboratory
Year of Publication
2005
Country of Publication
United States
Format
Report
Material
LSL (Laminated Strand Lumber)
LVL (Laminated Veneer Lumber)
Solid-sawn Heavy Timber
Topic
Mechanical Properties
Moisture
Keywords
Aspen
Douglas-Fir
Modulus of Elasticity
Modulus of Rupture
Southern Pine
Poplar
Relative Humidity
SPF
Temperature
Flexural Properties
Language
English
Research Status
Complete
Summary
Solid-sawn lumber (Douglas-fir, southern pine, Spruce– Pine–Fir, and yellow-poplar), laminated veneer lumber (Douglas-fir, southern pine, and yellow-poplar), and laminated strand lumber (aspen and yellow-poplar) were heated continuously at 82°C (180°F) and 80% relative humidity (RH) for periods of up to 24 months. The lumber was then reconditioned to room temperature at 20% RH and tested in edgewise bending. Little reduction occurred in modulus of elasticity (MOE) of solid-sawn lumber, but MOE of composite lumber products was somewhat reduced. Modulus of rupture (MOR) of solid-sawn lumber was reduced by up to 50% after 24 months exposure. Reductions in MOR of up to 61% were found for laminated veneer lumber and laminated strand lumber after 12 months exposure. A limited scope study indicated that the results for laminated veneer lumber in edgewise bending are also applicable to flatwise bending. Comparison with previous results at 82°C (180°F)/25% RH and at 66°C (150°F)/20% RH indicate that differences in the permanent effect of temperature on MOR between species of solid-sawn lumber and between solid-sawn lumber and composite lumber products are greater at high humidity levels than at low humidity levels. This report also describes the experimental design of a program to evaluate the permanent effect of temperature on flexural properties of structural lumber, with reference to previous publications on the immediate effect of temperature and the effect of moisture content on lumber properties.
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Effective Bonding Parameters for Hybrid Cross-Laminated Timber (CLT)

https://research.thinkwood.com/en/permalink/catalogue1368
Year of Publication
2017
Topic
Mechanical Properties
Connections
Material
CLT (Cross-Laminated Timber)
Author
Larkin, Blake
Organization
Oregon State University
Year of Publication
2017
Country of Publication
United States
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Topic
Mechanical Properties
Connections
Keywords
North America
Low-Grade
Adhesives
Bond Integrity
Polyurethane
Phenol-Resorcinol Formaldehyde
Lodgepole Pine
Douglas-Fir
Hemlock
Manufacturing
Language
English
Research Status
Complete
Summary
Cross-laminated timber (CLT) is a massive engineered wood product made of orthogonally bonded layers of solid-sawn lumber, and is intended for roof, floor, or wall applications. Although it was developed in Europe in the early 90s, CLT is relatively new to North America. CLT products must be certified for structural use. First North American product standard stipulating test methods and qualification criteria for benchmark structural properties and adhesive bond integrity in structural CLT is ANSI/APA PRG320-2012. These methods and criteria have been adapted from existing laminated timber products (glulam), sometimes disregarding substantial differences between parallel laminates and CLT, in which layers are perpendicular to each other. From the point of view of long term sustainability of the CLT industry in North America, the critical questions are: 1. Is it possible to use low-grade timber harvested in the Pacific Northwest region in CLT products without compromising critical engineering parameters? Utilization of low- grade lumber, which is typically under-valued, in value-added engineered products should reduce the pressure on the high end structural lumber supply and may also provide a substantial outlet for lower-grade lumber timber species, including beetle-killed pine (BKP) harvested in the affected areas. 2. Can alternative adhesive systems, currently used in related engineered wood products and manufactured by domestic industry, be successfully used in CLT production? This is an important question, and is related to the fact that polyurethane (PUR) is the primary adhesive currently used by CLT manufacturing industry, and is supplied worldwide by a single Europe-based company. This adhesive is optimized for the species commonly used in CLT products to-date. ANSI/APA PRG320-2012 standard allows alternative adhesive types (PRF and EPI are specifically named), but to-date, only one alternative (MUF) has been used in commercial products. The objective of this project is to determine effective adhesive systems and bonding pressures for the hybrid cross-laminated timber (CLT) combinations. A secondary objective is to evaluate the testing methods prescribed in PRG 320-2012 for cross-laminated bond integrity. Integrity of hybrid CLT layups was evaluated on small specimens derived from CLT billets fabricated in-house using test procedures and qualification criteria specified in ANSI/APA PRG 320-2012 section 8.2.3. Test results were compared to prescribed qualification criteria. The Hybrid CLT combinations for this study include both structural grade lumber and low-grade lumber. For a reference species, lodgepole pine was selected, since it is a member of the US-SPF group closely related to the European species commonly used for CLT construction. The structural-grade, local species will be represented by Douglas-fir, while the low-grade species will be represented by low-grade lodgepole Pine, Douglas-fir, and Western Hemlock. The two adhesive systems investigated were 1) polyurethane-based PUR (currently the most common adhesive used by the CLT industry), which will serve as a reference system, and 2) phenol-resorcinol formaldehyde (PRF), which will represent a potential domestic alternative. PRF was chosen because it is a cold setting adhesive commonly used by the engineered wood products industry in North America; however, no CLT manufacturers utilize this adhesive system. The variables included species combinations (6), adhesive types (2), and clamping pressures (3), with repetition of 9 specimens per combination coming from at least three different CLT billets. The specimen’s bond integrity was assessed by the qualification panel requirements in PRG 320-2012 section 8.2. The qualification tests are block shear and cyclic delamination. A combination must pass both of the test requirements to qualify. The results of the study show that, of the 36 combinations, six failed the block shear test requirements and twenty-five failed the delamination test requirements. The 10 variable combinations that passed both requirements were DDL10F, DDL40F, DPL40F, PPH10F, PPH69F, PPH10U, PPH40U, PPL10U, PPL69U, and PHL69U. Initial inspection of test results show that no single variable that seems to make a significant impact on the bond integrity. It did reveal that no combinations with the use of Douglas-fir as a face material and PUR as an adhesive met the requirement, and only one combination with western hemlock as a core material met the requirements. It is evident that the delamination test was the major restriction on whether or not a combination passes the bond qualification. We believe that the adaption of a delamination test standard designed for layers with parallel grains makes the passing requirement too strict for an orthogonally bonded product. In conclusion, there were 10 combinations that passed both bond integrity test requirements. It was unclear whether the species and/or grade combination, adhesive system, or clamping pressure made the biggest impact on the bond integrity. Relative to the reference adhesive (PUR), and species combination (lodgepole pine), the hybrid panels performed similarly and showed that certain species and/or grade combinations could pass the qualification requirements for specific requirements. The knowledge gained by this screening study will allow further qualification testing of the passing combinations per PRG320-2012. This also has the potential to supply the CLT manufacturing community with greater flexibility of manufacturing techniques and materials, as well as offer value to underutilized lumber.
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Effectiveness of Several NDE Technologies in Detecting Moisture Pockets and: Artificial Defects in Sawn Timber and Glulam

https://research.thinkwood.com/en/permalink/catalogue778
Year of Publication
2016
Topic
Serviceability
Material
Glulam (Glue-Laminated Timber)
Solid-sawn Heavy Timber
Application
Bridges and Spans
Author
Wacker, James
Senalik, Christopher
Wang, Xping
Jalinoos, Frank
Year of Publication
2016
Country of Publication
Austria
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Solid-sawn Heavy Timber
Application
Bridges and Spans
Topic
Serviceability
Keywords
Decay
Douglas-Fir
Moisture Pockets
Non-Destructive Evaluation
Scanning
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria
Summary
Several nondestructive evaluation (NDE) technologies were studied to determine their efficacy as scanning devices to detect internal moisture and artificial decay pockets. Large bridge-sized test specimens, including sawn timber and glued-laminated timber members, were fabricated with various internal defects. NDE Technologies evaluated in this research were ground penetrating radar (GPR), microwave scanning, ultrasonic pulse velocity, ultrasonic shear wave tomography, and impact echo methods. Each NDE technology was used to evaluate a set of seven test specimens over a 2-day period and then raw data scans were processed into two-dimensional, internal defect maps. Several parameters were, compared including the relative size, orientation, and moisture conditions of the internal defect. GPR was the most promising NDE technology and is currently being more rigorously evaluated within the laboratory. The study results will be useful in the further development of a reliable NDE scanning technique that can be utilized to inspect the primary structural components in historic covered timber bridges.
Online Access
Free
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Effect of Inclined Self-Tapping Screws Connecting Laminated Veneer Lumber on the Shear Resistance

https://research.thinkwood.com/en/permalink/catalogue2479
Year of Publication
2019
Topic
Connections
Mechanical Properties
Material
LVL (Laminated Veneer Lumber)

Enhancing Thermal and Mechanical Performance of Engineered Wood Product Adhesives using Novel Fire Retardant Nanoclays

https://research.thinkwood.com/en/permalink/catalogue2810
Year of Publication
2021
Topic
Mechanical Properties
Fire
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Oguzlu-Baldelli, Hale
Yu, Jason
Lee, George
Lam, Frank
Jiang, Feng
Organization
University of British Columbia
Year of Publication
2021
Country of Publication
Canada
Format
Report
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Mechanical Properties
Fire
Keywords
Adhesive
PUR
Bond Strength
Halloysite
pMDI
Douglas-Fir
SPF
Bonding Shear Strength
Language
English
Research Status
Complete
Summary
One component PUR adhesive is widely used in engineered wood products applications, such as cross-laminated timber (CLT). However, the dramatic deterioration of PUR adhesive bond strength at elevated temperature can out tremendously threat for tall wood building, especially under fire. In this project, we are aiming to improving the bond strength of the PUR adhesive at high temperature by incorporating chemically modified halloysite to improve the poor interface between inorganic fillers and the polymer matrices. To improve the interaction with PUR (Loctite UR20 by Henkel®), the halloysite was chemically grafted with polymeric diphenylmethane diisocyanate (pMDI) (pMDI-H). The effect of adding pMDI modified halloysite to the PUR adhesives was investigated in terms of nanofiller dispersibility, thermal and mechanical properties of the pMDI-halloysite-PUR composite film, and the bonding shear strength of the glued Douglas fir and Spruce-Pine-Fir (SPF) shear blocks under different temperature. Significant improvement of the bond shear strength can be observed with the addition of 5 and 10% of pMDI-modified PUR adhesive, and the key research findings are summarized as below, a. pMDI can be successfully grafted onto hydroxylated halloysites to improve its dispersibility in one-component PUR adhesive; b. Addition of pMDI-H into PUR adhesive can lead to improved glass transition temperature and storage modulus. In contrast, no significant enhancement was observed in h-H added PUR films due to the poor dispersibility; c. Addition of up to 10% h-H and pMDI-H did not show significant change of the shear strength at 20 °C for both Douglas Fir and SPF; d. Significant enhancement of shear strength at elevated temperature (60-100 °C) can be observed for 5% and 10% pMDI-H modified PUR adhesive, showing 17% improvement for Douglas Fir and 27-37% for SPF.
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Experimental Study on Flexural Performance of Glued-Laminated-Timber-Bamboo Beams

https://research.thinkwood.com/en/permalink/catalogue1387
Year of Publication
2018
Topic
Design and Systems
Mechanical Properties
Material
Other Materials
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Xu, Qingfeng
Leng, Yubing
Chen, Xi
Harries, Kent
Chen, Lingzhu
Wang, Zhuolin
Publisher
Springer Netherlands
Year of Publication
2018
Country of Publication
Netherlands
Format
Journal Article
Material
Other Materials
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Design and Systems
Mechanical Properties
Keywords
Bamboo
Spruce
Douglas-Fir
Flexural Performance
Strengthening
Language
English
Research Status
Complete
Series
Materials and Structures
ISSN
1871-6873
Summary
Engineered bamboo, produced through the technique of gluing and reconstituting, has better mechanical properties than round bamboo and some wood products. This paper studies the flexural performance of laminated beams produced with timber and engineered bamboo. The six-layer beams were made from Douglas fir, spruce, bamboo scrimber and laminated bamboo, or a combination of these. It is confirmed that glued-laminated wood beams producedwith wood of weak strength, like spruce, can be strengthened by gluing engineered bamboo lumbers on the outer faces, thus achieving better utilization of the fast growing economic wood species. Flexural failure of the laminated beams was primarily triggered by tensile fracture of the bottom fiber in mid-span, followed by horizontal tearing beside the broken surface. No relative slip between layers was observed before failure, therefore the flexural capacity of the laminated beams can be predicted using equilibrium and compatibility conditions according to the plane section assumption
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Free
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Experimental Study on Loading Capacity of Glued-Laminated Timber Arches Subjected to Vertical Concentrated Loads

https://research.thinkwood.com/en/permalink/catalogue2581
Year of Publication
2020
Topic
Design and Systems
Material
Glulam (Glue-Laminated Timber)
Application
Arches
Author
Zhou, Jiale
Chuanxi, Li
Ke, Lu
He, Jun
Wang, Zhifeng
Publisher
Hindawi
Year of Publication
2020
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Application
Arches
Topic
Design and Systems
Keywords
In-Plane Loading
Capacity
Douglas-Fir
Model
Failure Modes
Language
English
Research Status
Complete
Series
Advances in Civil Engineering
Summary
Glued-laminated timber arches are widely used in gymnasiums, bridges, and roof trusses. However, studies on their mechanical behaviours and design methods are still insufficient. This paper investigates the in-plane loading capacity of circular glued-laminated timber arches made of Douglas fir. Experiments were conducted on four timber-arch models with different rise-to-span ratios under concentrated loads at mid-span and quarter-point locations. The structural responses, failure modes, and loading capacity of the timber arch specimens were obtained. The results show that the timber arches presented symmetric and antisymmetric deformation under mid-point and quarter-point loading conditions, respectively. The downward shifting of the neutral axis of the cross section was observed under mid-point loading condition, which contributes to higher loading capacity compared to that under quarter-point loading condition. The loading condition significantly affects the ultimate loads and the strain distribution in the cross section. Based on the design formula in current standards for timber structures, an equivalent beam-column method was introduced to estimate the loading capacity of the laminated timber arches under vertical concentrated loads. The moment amplification factor in the formula was compared and discussed, and the value provided in the National Design Specification for Wood Construction was recommended with acceptable accuracy.
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Free
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Factors Affecting Distribution of Borate to Protect Building Envelope Components from Biodegradation

https://research.thinkwood.com/en/permalink/catalogue1586
Year of Publication
2012
Topic
Moisture
Serviceability
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Saadat, Nazmus
Cooper, Paul
Organization
University of Toronto
Year of Publication
2012
Country of Publication
Canada
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Moisture
Serviceability
Keywords
Preservatives
Borate
Building Envelope
Moisture Content
Spruce
Douglas-Fir
Language
English
Research Status
Complete
Summary
Borate can be a potential candidate to protect building envelope components from biodegradation as it has low toxicity and can penetrate wood without pressure treatment, even in the refractory species commonly used in construction industries as structural components. In this research, wood moisture content, grain direction, formulation and species that affect the diffusion of borate in refractory species were investigated. Two highly concentrated formulations were applied and a novel approach (borate bandage) was used to keep the preservative on the surface and enhance the diffusion by reducing surface drying. From ANOVA test for different diffusion periods and depths of penetration, it was found that grain directions and moisture content are significant factors. A mould test was performed, the diffusion co-efficients were calculated and some recommendations were made about the quantity required to protect a specific volume of wood considering the distance moved by diffusion and volume treated in different directions.
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Free
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20 records – page 1 of 2.