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Acoustic emission monitoring of wood materials and timber structures: A critical review

https://research.thinkwood.com/en/permalink/catalogue3187
Year of Publication
2022
Topic
Acoustics and Vibration
Author
Nasir, Vahid
Ayanleye, Samuel
Kazemirad, Siavash
Sassani, Farrokh
Adamopoulos, Stergios
Organization
The University of British Columbia
Mississippi State University
Iran University of Science and Technology
Swedish University of Agricultural Sciences
Publisher
Elsevier
Year of Publication
2022
Format
Journal Article
Topic
Acoustics and Vibration
Keywords
Non-Destructive Evaluation
Acoustic Emission
Structural Health Monitoring
Wood Machining
Kiln Drying
Termite Detection
Thermally Modified Timber
Wood Fracture
Damage Detection
Research Status
Complete
Series
Construction and Building Materials
Summary
The growing interest in timber construction and using more wood for civil engineering applications has given highlighted importance of developing non-destructive evaluation (NDE) methods for structural health monitoring and quality control of wooden construction. This study, critically reviews the acoustic emission (AE) method and its applications in the wood and timber industry. Various other NDE methods for wood monitoring such as infrared spectroscopy, stress wave, guided wave propagation, X-ray computed tomography and thermography are also included. The concept and experimentation of AE are explained, and the impact of wood properties on AE signal velocity and energy attenuation is discussed. The state-of-the-art AE monitoring of wood and timber structures is organized into six applications: (1) wood machining monitoring; (2) wood drying; (3) wood fracture; (4) timber structural health monitoring; (5) termite infestation monitoring; and (6) quality control. For each application, the opportunities that the AE method offers for in-situ monitoring or smart assessment of wood-based materials are discussed, and the challenges and direction for future research are critically outlined. Overall, compared with structural health monitoring of other materials, less attention has been paid to data-driven methods and machine learning applied to AE monitoring of wood and timber. In addition, most studies have focused on extracting simple time-domain features, whereas there is a gap in using sophisticated signal processing and feature engineering techniques. Future research should explore the sensor fusion for monitoring full-scale timber buildings and structures and focus on applying AE to large-size structures containing defects. Moreover, the effectiveness of AE methods used for wood composites and mass timber structures should be further studied.
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Bamboo-based composites: A review on fundamentals and processes of bamboo bonding

https://research.thinkwood.com/en/permalink/catalogue3201
Year of Publication
2022
Topic
General Information
Author
Nkeuwa, William Nguegang
Zhang, Jialin
Semple, Kate E.
Chen, Meiling
Xia, Yeling
Dai, Chunping
Organization
University of British Columbia
West Fraser Timber Co. Ltd
Publisher
Elsevier
Year of Publication
2022
Format
Journal Article
Topic
General Information
Keywords
Bamboo
Engineered Bamboo
Adhesion
Research Status
Complete
Series
Composite Part B: Engineering
Summary
Sustainable development and applications of bamboo and bamboo-wood composites require better understanding and optimization of bamboo bonding. This paper provides a critical review of bamboo composite bonding in relation to wood bonding characteristics and processes. A polylamellate cell wall structure, low tissue porosity and permeability, and poor surface wettability hamper bamboo bonding with most wood adhesives. Bamboo element preparation, treatment and adhesive modification must be optimized in conjunction with more efficient material utilization and processes. Development of bond qualification standards similar to engineered wood products but tailored to stronger bamboo tissues are essential for structural bamboo composites. While phenolics are still commonly used for structural bamboo composite bonding, the industry is shifting away from formaldehyde systems. Isocyanate-based resins offer viable solutions, especially for bamboo strand composites. Changes in bamboo surface pH and wettability after industrial treatments like bleaching and pressure-steaming likely explain the variations in bonding performance with common wood adhesives. Hybrid bamboo-wood composites are promising cost-effective approaches for the engineered bamboo industry leading to viable building products. Future research subjects related to bamboo composite bonding are also discussed.
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CLT Infill Panels in Steel Moment Resisting Frames as a Hybrid Seismic Force Resisting System

https://research.thinkwood.com/en/permalink/catalogue107
Year of Publication
2013
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Dickof, Carla
Organization
University of British Columbia
Year of Publication
2013
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Seismic
Keywords
National Building Code of Canada
Timber-Steel Hybrid
Seismic Force Resisting System
Research Status
Complete
Summary
This paper examines CLT-steel hybrid systems at three, six, and nine storey heights to increase seismic force resistance compared to a plain wood system. CLT panels are used as infill in a steel moment frame combining the ductility of a steel moment frame system with a stiffness and light weight of CLT panels. This system allows for the combination of high strength and ductility of steel with high stiffness and light weight of timber. This thesis examines the seismic response of this type of hybrid seismic force resisting system (SFRS) in regions with moderate to high seismic hazard indices. A detailed non-linear model of a 2D infilled frame system and compared to the behavior of a similar plain steel frame at each height. Parametric analysis was performed determining the effect of the panels and the connection configuration, steel frame design, and panel configuration in a multi-bay system. Static pushover loading was applied alongside semi-static cyclic loading to allow a basis of comparison to future experimental tests. Dynamic analysis using ten ground motions linearly scaled to the uniform hazard spectra for Vancouver, Canada with a return period of 2% in 50 years as, 10% in 50 years, and 50% in 50 years to examine the effect of infill panels on the interstorey drift of the three, six, and nine storey. The ultimate and yield strength and drift capacity are determined and used to determine the overstrength and ductility factors as described in the National Building Code of Canada 2010.
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Comparison of Environmental Performance of a Five-Storey Building Built with Cross-Laminated Timber and Concrete

https://research.thinkwood.com/en/permalink/catalogue65
Year of Publication
2012
Topic
Energy Performance
Environmental Impact
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Chen, Yue
Organization
University of British Columbia
Year of Publication
2012
Format
Report
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Energy Performance
Environmental Impact
Keywords
Canada
Concrete
Energy Consumption
Environmental
Mid-Rise
North America
Office Buildings
Passive Buildings
Research Status
Complete
Summary
Cross Laminated Timber (CLT), which is made by laminating dimension lumber at right angles, is an innovative high-performance building material that offers many positive attributes including renewability, high structural stability, storage of carbon during the building life, good fire resistance, possibility of material recycling and reuse. It is conceptually a sustainable and cost effective structural timber solution that can compete with concrete in non-residential and multi-family mid-rise building market. Therefore, there is a need to understand and quantify the environmental attribute of this building system in the context of North American resources, manufacturing technology, energy constraints, building types, and construction practice. This study is to compare energy consumption of two building designs using different materials, i.e. CLT and concrete. The designs were based on a five-storey office building, Discovery Place-Building 12, which is located in Burnaby, British Columbia, at 4200 Canada Way. The existing building was built with reinforced concrete. Embodied energy was calculated based on the total amount of material required for each of the building systems. Operational energy was calculated using eQUEST, an energy usage modeling software tool. The environmental impacts of the buildings were evaluated by comparing the total energy consumption through the building life. CLT has lower non-renewable energy consumption compared to concrete in terms of material acquisition, manufacturing and transportation. Previous studies shew that operational energy accounts for the main amount of total energy use in buildings during their service life. Hence, the importance of embodied energy increases by reducing operational energy consumption. CLT has lower embodied energy compared to concrete. Therefore, the advantage of using CLT as a construction material is becoming greater by designing low energy or passive buildings.
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Composite action in mass timber floor and beam systems connected with self-tapping wood screws

https://research.thinkwood.com/en/permalink/catalogue3010
Year of Publication
2020
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
Application
Floors
Author
Natalini, Giulia
Organization
University of British Columbia
Year of Publication
2020
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
Application
Floors
Topic
Mechanical Properties
Keywords
Push-Out Tests
Bending Tests
Self-Tapping Screws
T-beam
Research Status
Complete
Summary
One of the challenges in mass timber construction is the design of efficient floor systems. This thesis focuses on studying composite T-beams, connecting Spruce-Pine-Fir Cross Laminated Timber (CLT) panels and Douglas-Fir Glued-Laminated timber (glulam) beams. In this study, three different types of self-tapping wood screws (ASSY SK, ASSY Ecofast, and ASSY VG), inserted at different angles, were investigated. Firstly, small-scale experimental tests were performed to investigate the strength and stiffness of the screws when submitted to lateral shear loads. It was found that the most promising fastener was the ASSY VG and that changing the angle of installation of the screws from 90° to the wood grain, to 45°, increased the strength and the stiffness of the studied connection. Secondly, full-scale composite beams experimental tests were completed to validate mechanistic-based and computational methods used to predict the effective bending stiffness of the composite T-beam. A degree of composite action achieved for the experimental T-beams was calculated through the studied methods. It was found that the studied T-beam achieved a moderately high percentage of composite action. Moreover, the methods were compared in terms of prediction accuracy, computational difficulty, required number of parameters, and versatility. Finally, parametric analyses were completed to gain insight into the structural performance of the composite beam when varying the number of CLT plies, the width of the CLT panel and of the glulam beams, as well as the length of the T-beam. Results indicate, conservatively, that the proposed connection, with a 3-ply CLT panel and a 130x190mm glulam beam, can be used to span 6m, maintaining a flange width of 2.8m. The results also suggest that with a 5-ply CLT panel and a 365x190mm glulam beam, it is possible to manufacture a 10m long T-beam that spans 3m laterally and supports live loads compatible with office use and occupancy.
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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 Laminated Veneer Lumber (LVL). The bending stiffness of a joint was evaluated by the slip modulus between the connector plate and CLT under shear. The LVL based connector had 87% of the stiffness compared to the steel plate connector tested in Phase I, while performed much better at the initial period of the loading. Considering other factors, including manufacturing cost, assembly time, structural integrity, and fire protection, the LVL connection was found to be a good solution for joining the minor direction of CLT plates. An analytical model was proposed to establish the relationship between the slip modulus and the joint stiffness.
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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. The connections were designed and tested to quantify their performance. Conventional methods to build timber modules based on platform construction may not be most suitable for midrise to tall stackable buildings, due to the weak compression perpendicular to grain property of wood. Balloon construction is proposed here to manufacture individual modules so that non-disruptive vertical load transfer path is maintained along the structural height. Three screwed connections were tested to evaluate the load transfer between the elements, with steel angle brackets and Laminated Veneer Lumber (LVL) blocks. Screws at 90° were found to be inadequate for this application due to the low stiffness and high variation. When screws were installed at 45°, both the steel plates and LVL blocks had high stiffness, high strength, and good ductility.
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Contemporary and Novel Hold-Down Solutions for Mass Timber Shear Walls

https://research.thinkwood.com/en/permalink/catalogue2941
Year of Publication
2022
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Author
Tannert, Thomas
Loss, Cristiano
Organization
University of Northern British Columbia
University of British Columbia
Editor
Tullini, Nerio
Publisher
MDPI
Year of Publication
2022
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Topic
Mechanical Properties
Keywords
Self-Tapping Screws
Internal-Perforated Steel Plates
Hyperelastic Bearing Pads
Proprietary Connections
Research Status
Complete
Series
Buildings
Summary
‘Mass timber’ engineered wood products in general, and cross-laminated timber in particular, are gaining popularity in residential, non-residential, as well as mid- and high-rise structural applications. These applications include lateral force-resisting systems, such as shear walls. The prospect of building larger and taller timber buildings creates structural design challenges; one of them being that lateral forces from wind and earthquakes are larger and create higher demands on the ‘hold-downs’ in shear wall buildings. These demands are multiple: strength to resist loads, lateral stiffness to minimize deflections and damage, as well as deformation compatibility to accommodate the desired system rocking behaviour during an earthquake. In this paper, contemporary and novel hold-down solutions for mass timber shear walls are presented and discussed, including recent research on internal-perforated steel plates fastened with self-drilling dowels, hyperelastic rubber pads with steel rods, and high-strength hold-downs with self-tapping screws.
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Conventional and Novel Timber Steel Hybrid Connections: Testing, Performance and Assessment

https://research.thinkwood.com/en/permalink/catalogue187
Year of Publication
2015
Topic
Connections
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Schneider, Johannes
Organization
University of British Columbia
Year of Publication
2015
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Connections
Seismic
Keywords
Timber-Steel Hybrid
Fasteners
Quasi-Static
Monotonic Loading
Cyclic Loading
Brackets
Tube Connections
Research Status
Complete
Summary
The focus of this research is the connection between steel frame and the infill wall. Over 100 conventional bracket-type connections with various combinations of bracket and fasteners with cross-laminated timber were tested, investigated and assessed for damage under seismic loading protocols for a hybrid application. An energy-based formulation according to Krätzig was applied to calculate the development of the damage index, and the resulting index was validated with visual observation. Six of the connections were modeled in OpenSees. For the modeling, a CUREE-10 parameter model was chosen to reproduce the test curves. The load-displacement results from both test and model were analyzed; the first method according to ASTM standards, where the envelope curve of the hysteretic results are considered and plotted in an equivalent energy elastic-plastic curve (EEEP). The second analyzing method used, was Krätzig’s damage accumulation model. Throughout all six combinations and both loading directions (parallel- and perpendicular-to-the-grain) a major difference was found in the analyzing methods. The EEEP curve roughly approximates the performance but with the damage accumulation method showed that analysis of the subsequent cycles is required to better reflect the empirical performance of the connections. To avoid the extensive destruction of a bracket type connection after completion of seismic loadings, a new approach was chosen. It was found that a tube connection can obtain comparably similar strength results as a conventional bracket connection. The computed mechanical properties of bracket-type and tube-type connections were compared and evaluated. The new tube connection showed great potential for future timber-steel hybrid structures and their connecting challenge. A total of 27 connection assemblies were tested under quasi-static monotonic and reversed cyclic loads. The tube connections showed two major differences when compared to traditional bracket connections: i) the completely linear elastic behaviour at the beginning, and ii) the continued load increase after yielding. Both phenomena are founded in the geometry of that connector effectively making the novel connector a very promising alternative.
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53 records – page 1 of 6.