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Connection and Performance of Two-Way CLT Plates

https://research.thinkwood.com/en/permalink/catalogue1482
Year of Publication
2018
Topic
Mechanical Properties
Connections
Material
CLT (Cross-Laminated Timber)
Application
Floors
Roofs
Author
Zhang, Chao
Lee, George
Lam, Frank
Organization
University of British Columbia
Year of Publication
2018
Format
Report
Material
CLT (Cross-Laminated Timber)
Application
Floors
Roofs
Topic
Mechanical Properties
Connections
Keywords
Two-Way
Bending Test
Modulus of Elasticity
Self-Tapping Screws
Glued-In-Rod
Steel Connectors
Steel Plates
Research Status
Complete
Summary
The two-way action of Cross Laminated Timber (CLT) is often ignored in the design of CLT due to its complexity. But in some cases, for example, large span timber floor/roof, the benefit of taking the two-way action into account may be considerable since it is often deflection controlled in the design. Furthermore CLT panels are typically limited to widths of less than 3 m. therefore, for practical applications, engaging CLT panels in two-way action as a plate in bending would require connecting two panels in the width/minor direction to take out-of-plane loading. To address this technically difficult situation, an innovative connection was developed to join the CLT panels in the minor direction to form a large continuous two-way plate. The two-way action of CLT was also quantified. Static bending test was conducted on CLT panels in the major and minor directions to measure the Modulus of Elasticity (MOE). This provided a benchmark for the following connection test, and data for the future development of computer modeling. The average apparent MOE was 9.09 GPa in the major direction and 2.37 GPa in the minor direction. Several connection techniques were considered and tested, including self-tapping wood screws, glued in steel rods, and steel connectors. One connecting system was found to be effective. For the panel configuration considered, the system was consisted of steel plates, self-tapping wood screws, and 45° screw washers. Two steel plates were placed on the tension side with sixteen screws, and one steel plates was placed on the compression side with four screws. When the screws were driven into the wood, the screws were tightly locked with the washers and steel plates, and at the same time, the wood members were pulled together by the screws. This eliminated any original gap within the connection. The connector was installed to join two CLT members in the minor direction. They were tested under bending with the same setup as above. The connected panels had an average apparent MOE of 2.37 GPa, and an average shear-free MOE of 2.44 GPa, both of which were higher than the counterpart in the full panels. The moment capacity of the connected panels was also high. The minimum moment capacity was 3.2 times the design value. Two large CLT panels were tested under concentrated loading with four corners simply supported. The deflection of nine locations within the panels was measured. This data will be used to validate the computer modeling for CLT two-way action.
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Connection and Performance of Two-Way CLT Plates Phase II

https://research.thinkwood.com/en/permalink/catalogue2086
Year of Publication
2019
Topic
Mechanical Properties
Connections
Material
CLT (Cross-Laminated Timber)
PSL (Parallel Strand Lumber)
LVL (Laminated Veneer Lumber)
Author
Zhang, Chao
Asselstine, Julian
Lee, George
Lam, Frank
Organization
University of British Columbia
Year of Publication
2019
Format
Report
Material
CLT (Cross-Laminated Timber)
PSL (Parallel Strand Lumber)
LVL (Laminated Veneer Lumber)
Topic
Mechanical Properties
Connections
Keywords
Deflection
Two-Way
Bending
Finite Element Method
Model
Research Status
Complete
Summary
In Phase I of Developing Large Span Two Way CLT Floor System (2017-18) we studied the performance of a steel plate connection system for the minor direction of CLT plates. The connected specimens had higher stiffness and strength compared to intact members under bending. In Phase II (2018-19) we designed and tested another connector based on...
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Connections for Stackable Heavy Timber Modules in Midrise to Tall Wood Buildings

https://research.thinkwood.com/en/permalink/catalogue2087
Year of Publication
2019
Topic
Connections
Design and Systems
Seismic
Material
LVL (Laminated Veneer Lumber)
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Zhang, Chao
Lee, George
Lam, Frank
Organization
University of British Columbia
Year of Publication
2019
Format
Report
Material
LVL (Laminated Veneer Lumber)
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Connections
Design and Systems
Seismic
Keywords
Modular
Intra-module Connection
Inter-module Vertical Connection
Inter-module horizontal Connection
Mid-Rise
Tall Wood
Screws
Load Transfer
Steel Angle Bracket
Stiffness
Strength
Ductility
Research Status
Complete
Summary
In Phase I (2018-19) of this project on Prefabricated Heavy Timber Modular Construction, three major types of connections used in a stackable modular building were studied: intramodule connection, inter-module vertical connection, and inter-module horizontal connection. The load requirement and major design criteria were identified...
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Developing a Large Span Timber-based Composite Floor System for Highrise Office Buildings Phase I

https://research.thinkwood.com/en/permalink/catalogue2803
Year of Publication
2021
Topic
Design and Systems
Material
CLT (Cross-Laminated Timber)
LVL (Laminated Veneer Lumber)
LSL (Laminated Strand Lumber)
Glulam (Glue-Laminated Timber)
Application
Floors
Author
Zhang, Chao
Lee, George
Lam, Frank
Organization
University of British Columbia
Year of Publication
2021
Format
Report
Material
CLT (Cross-Laminated Timber)
LVL (Laminated Veneer Lumber)
LSL (Laminated Strand Lumber)
Glulam (Glue-Laminated Timber)
Application
Floors
Topic
Design and Systems
Keywords
Box Girder
Timber Composite Floor
Span
High-Rise
Tall Wood Buildings
Stiffness
Composite Action
Research Status
Complete
Summary
This project proposes a timber-based composite floor that can span 12 m and be used in the construction of 40+ story office buildings. This floor system integrates timber panels and timber beams to form a continuous box girder structure. The timber panels function as the flanges and the timber beams as the web. The beams are spaced and connected to the flange panels so that sufficient bending stiffness of a 12 m span can be achieved via the development of composite action. The current phase of this project studied the performance of the connections between timber elements in the proposed composite member. Six types of connections using different flange material and connection techniques were tested: Cross Laminated Timber (CLT), Laminated Strand Lumber (LSL), Laminated Veneer Lumber (LVL), and Post Laminated Veneer Lumber (PLVL). Glulam was used as the web. The majority of the connections used self-tapping wood screws except one had notches. The load-carrying capacity, stiffness, and ductility of the connections were measured. The stiffness of CLT, LSL, and PLVL connections was in the same range, 19-20 kN/mm per screw. Amongst the three, LSL had the highest peak load and PLVL had the highest proportional limit. The stiffness of the two LVL screw connections was around 13 kN/mm. The notched LVL connection had significantly higher stiffness than the rest, and its peak load was in the same range as LSL, but the failure was brittle. LVL was used to manufacture the full scale timber composite floor element. With a spacing of 400 mm, the overall stiffness reached 33689 N
mm2×109, which was 2.5 times the combined stiffness of two Glulam beams. The predicted overall stiffness based on Gamma method was within 5% of the tested value, and the estimated degree of composite action was 68%. From both the test results and analytical modeling, the number of screws may be further reduced to 50% or less of the current amount, while maintaining a high level of stiffness. Future work includes testing the composite floor under different screw spacings, investigating the effect of concrete topping, and the connections between floor members and other structural elements.
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Development of Mass Timber Wall System Based on Nail Laminated Timber

https://research.thinkwood.com/en/permalink/catalogue2526
Year of Publication
2020
Topic
Design and Systems
Material
NLT (Nail-Laminated Timber)
Application
Walls
Author
Zhang, Chao
Lee, George
Lam, Frank
Organization
Timber Engineering and Applied Mechanics (TEAM) Laboratory
Year of Publication
2020
Format
Report
Material
NLT (Nail-Laminated Timber)
Application
Walls
Topic
Design and Systems
Keywords
Shear
Stiffness
Fasteners
Fastener Type
Load
Research Status
Complete
Summary
This project studied the feasibility and performance of a mass timber wall system based on Nail Laminated Timber (NLT) for floor/wall applications, in order to quantify the effects of various design parameters. Thirteen 2.4 m × 2.4 m shear walls were manufactured and tested in this phase. Together with another five specimens tested before, a total eighteen shear wall specimens and ten configurations were investigated. The design variables included fastener type, sheathing thickness, number of sheathings, sheathing material, nailing pattern, wall opening, and lumber orientation. The NLT walls were made of SprucePine-Fir (SPF) No. 2 2×4 (38 mm × 89 mm) lumber and Oriented Strand Lumber (OSB) or plywood sheathing. They were tested under monotonic and reverse-cyclic loading protocols, in accordance with ASTM E564-06 (2018) and ASTM E2126-19, respectively. Compared to traditional wood stud walls, the best performing NLT based shear wall had 2.5 times the peak load and 2 times the stiffness at 0.5-1.5% drift, while retaining high ductility. The advantage of these NLT-based wall was even greater under reverse-cyclic loading due to the internal energy dissipation of NLT. The wall with ring nails had higher stiffness than the one with smooth nails. But the performance of ring nails deteriorated drastically under reverse-cyclic loading, leading to a considerably lower capacity. Changing the sheathing thickness from 11 mm to 15 mm improved the strength by 6% while having the same initial stiffness. Adding one more face of sheathing increased the peak load and stiffness by at least 50%. The wall was also very ductile as the load dropped less than 10% when the lateral displacement exceeded 150 mm. The difference created by sheathing material was not significant if they were of the same thickness. Reducing the nailing spacing by half led to a 40% increasing in the peak load and stiffness. Having an opening of 25% of the area at the center, the lateral capacity and stiffness reached 75% or more of the full wall. A simplified method to estimate the lateral resistance of this mass timber wall system was proposed. The estimate was close to the tested capacity and was on the conservative side. Recommendations for design and manufacturing the system were also presented.
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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
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
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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Fire Safe Glued Massive Timber Members Adhesive Bonding Performance under Elevated Temperature -Tests Report

https://research.thinkwood.com/en/permalink/catalogue169
Year of Publication
2013
Topic
Fire
Mechanical Properties
Material
Solid-sawn Heavy Timber
Author
Zhang, Chao
Yan, Huijun
Lee, George
Lam, Frank
Organization
Forestry Innovation Investment
Year of Publication
2013
Format
Report
Material
Solid-sawn Heavy Timber
Topic
Fire
Mechanical Properties
Keywords
Temperature
Adhesives
Bondlines
Polyurethane
Douglas-Fir
Hemlock
SPF
Phenol-Resorcinol Formaldehyde
Epoxy
Research Status
Complete
Summary
This project was conducted to quantify the performance of adhesives bond lines under shear load subject to elevated temperature. The results add to the understanding of the performance of polyurethane adhesive bond lines under elevated temperatures to address areas of fire safety concern under the current building codes. The project focused on studying the shear bond capacity of three wood species by using 3 types of adhesives with/without nanoclay treatment at 4 temperature levels. The three wood species are Douglas-Fir, Hemlock and SPF. The adhesives are polyurethane (PU), Phenol-Resorcinol-Formaldehyde (PRF) and Epoxy. PU and PRF specimens were also tested with nanoclay treatment and without nanoclay treatment. Epoxy specimens were tested without nanoclay treatment only. The temperature levels considered were room temperature (about 20 °C), 60°C, 80°C and 100°C. The results indicate that the influence of elevated temperature on the shear bond strength of PU and PRF adhesive was in the range of 20 to 30% regardless of nanoclay treatment. Regardless of species, PU or PRF, with or without nanoclay, the average shear strength for 100°C oven temperature treatment ranged from 6.0 to 7.5 MPa. In the case of SPF PU specimens treatment with nanoclay reduced the variability of shear strength significantly from 12% at room temperature to 5% after 100°C oven treatment. This is an important aspect that needs further verification for enhancement of performance. Finally the data in this study can be used to support modeling of timber component subjected to elevated temperature.
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Study of Massive Timber Walls based on NLT and Post Laminated LVL

https://research.thinkwood.com/en/permalink/catalogue1585
Year of Publication
2018
Topic
Connections
Mechanical Properties
Material
LVL (Laminated Veneer Lumber)
NLT (Nail-Laminated Timber)
Application
Shear Walls
Author
Zhang, Chao
Lee, George
Lam, Frank
Organization
University of British Columbia
Year of Publication
2018
Format
Report
Material
LVL (Laminated Veneer Lumber)
NLT (Nail-Laminated Timber)
Application
Shear Walls
Topic
Connections
Mechanical Properties
Keywords
Shear Tests
Glue Lines
Lateral Loading
Sheathing
Load Carrying Capacity
Stiffness
Energy Dissipation
Shear Strength
Research Status
Complete
Summary
Currently the massive timber shear walls are mainly made from Cross Laminated Timber (CLT), which possesses a high in-plane shear strength and rigidity. But only part of its elements (mainly the vertically aligned laminae) are engaged in carrying the vertical load and that could be a limitation when designing taller timber structures or wherever higher vertical load is present. This project studied alternative solutions to massive timber shear wall system, based on Nailed Laminated Timber (NLT) and post laminated LVL (Laminated Veneer Lumber). The test was conducted on three levels: shear test on glue/nail line, bending-shear test on a small element, and full size wall test under lateral loading. The former two tests investigated the properties of basic elements in NLT and post laminated LVL. The results were used to design and predict the performance of full size shear walls. The NLT walls were tested under two conditions: without sheathing and with plywood sheathing. The wall without sheathing had the lowest load-carrying capacity and lowest stiffness. Adding plywood sheathing significantly increased its strength and stiffness. The failure in the wall with sheathing was at the sheathing connections, in the forms of nail withdrawal, nail head pull through, and nail breakage. The NLT wall with sheathing had a peak load up to 60% higher than the comparable light wood frame wall, also with a higher stiffness and better ductility. NLT shear walls have an internal energy dissipating capacity which CLT and post laminated LVL walls lack. The post laminated LVL walls behaved as a rigid plate under lateral loading, with little internal deformation. The failure occurred at the holdowns not within the wall. The size effect of its shear strength was studied and an equation was developed to calculate the shear strength of a large size wall plate. Both products have efficient vertical load bearing mechanism by arranging all elements in the vertical direction. They may serve as alternative to light wood frame walls or CLT walls. Some guidelines for the application and design of NLT shear walls and post laminated LVL shear walls were proposed.
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8 records – page 1 of 1.