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28 records – page 1 of 3.

Cross-Laminated Timber Engineering: Improvement and Application

https://research.thinkwood.com/en/permalink/catalogue1366
Year of Publication
2014
Topic
Design and Systems
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Kramer, Anthonie
Organization
Oregon State University
Year of Publication
2014
Country of Publication
United States
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Design and Systems
Seismic
Keywords
Poplar
Energy Dissipation
Rocking Walls
Language
English
Research Status
Complete
Summary
The development of cross-laminated timber (CLT) panel technology has opened up new opportunities for wood in tall buildings. Several characteristics including seismic performance and speed of construction have raised interest among designers. As CLT gains acceptance in the industry, alternative structural solutions need to be investigated to improve performance of CLT as a building material. The first study presented is an assessment of the viability of hybrid poplar for use in CLT panels. Hybrid poplar is a low density species, which is not typically considered for structural applications. Low density species have the potential to improve the structural efficiency of CLT panels. The tests conducted are based on the qualification of panels outlined in the ANSI/APA PRG-320: Standard for Performance-Rated Cross-Laminated Timber to determine the structural viability of the CLT panels. The second study presented is an investigation of a new alternative energy dissipation solution to be used with cross-laminated timber rocking walls for seismic design. The energy dissipators are designed as a structural fuse which can be easily replaced after failure following a large seismic event. The results of this study give insight to alternative solutions for CLT to improve upon current applications.
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Optimizing Bonding Conditions for Cross Laminated Timber (CLT) Panels Using Low Density Hybrid Poplar

https://research.thinkwood.com/en/permalink/catalogue1424
Year of Publication
2015
Topic
Design and Systems
Material
CLT (Cross-Laminated Timber)
Author
Weidman, Aaron
Organization
Oregon State University
Year of Publication
2015
Country of Publication
United States
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Topic
Design and Systems
Keywords
Bond Integrity
Poplar
Standards
Non-Structural Lumber
Language
English
Research Status
Complete
Summary
Cross Laminated Timber (CLT) technology has been growing in the EU and Canada since the early 1990's and utilizes the mechanical properties of structural grade lumber to create a strong panel product for use in floor, ceiling and wall systems. The hypothesis of this project was that CLT panels made from non-structural lumber from lightweight species could also meet the performance criteria of the CLT product Standard. The objective of this project was to compare bond integrity in an optimized hybrid poplar CLT panel with standard CLT performance criteria Standard bond integrity tests were performed on CLT samples constructed using two adhesive types and three clamping pressure levels in order to find combinations that may pass the CLT product standard requirements. A lightweight structural CLT product made from hybrid poplar could be used as a model for other low density CLT products made from other less utilized resources.
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Structural Testing for Framework Office Building in Portland, OR

https://research.thinkwood.com/en/permalink/catalogue1829
Year of Publication
2017
Topic
Design and Systems
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
Application
Walls
Wood Building Systems
Organization
Oregon State University
Portland State University
Year of Publication
2017
Country of Publication
United States
Format
Report
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
Application
Walls
Wood Building Systems
Topic
Design and Systems
Mechanical Properties
Keywords
Crushing Test
In-Plane Shear Test
Beam-Column Connection
Panels
Earthquake
Language
English
Research Status
Complete
Series
Framework: An Urban + Rural Design
Summary
A. Structural Test Results Summary B. Test 1, 2, 3: 1. CLT Crushing Test Report 2. Bare CLT Wall Panel Test Report 3. CLT In-Plane Shear Wall Test Report C. Glulam Beam-Column Connection Test Report
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Structural Tests of Concrete Composite-Cross-Laminated Timber Floors

https://research.thinkwood.com/en/permalink/catalogue2830
Year of Publication
2017
Topic
Connections
Mechanical Properties
Serviceability
Material
CLT (Cross-Laminated Timber)
Timber-Concrete Composite
Application
Floors
Decking
Author
Higgins, Christopher
Barbosa, R. Andre
Blank, Curtis
Organization
Oregon State University
Publisher
Oregon State University
Year of Publication
2017
Country of Publication
United States
Format
Report
Material
CLT (Cross-Laminated Timber)
Timber-Concrete Composite
Application
Floors
Decking
Topic
Connections
Mechanical Properties
Serviceability
Keywords
Bending Behaviour
Shear Connection
Long-term Behaviour
TCC
Orthrotropic Plates
Language
English
Research Status
Complete
Summary
Experimental tests of a composite concrete-cross-laminated timber (CLT) floor system were conducted. The floor system was constructed with 5-ply CLT panels (6.75 in. thick) made composite with a 2.25 in. thick reinforced concrete topping slab. Four series of tests were performed using different specimen configurations and laboratory testing methods. Tests included: (1) Comparative one-way bending tests (CB) to evaluate the performance of alternative shear connectors used to join the concrete slab to the CLT panel; (2) Orthotropic stiffness and strength tests (OS) to evaluate the elastic orthotropic stiffness of the deck system and provide strength results for weak-axis bending and negative moment strength; (3) Full-scale system performance tests (FS) of a continuous floor span to establish strength at realistic span lengths and the influence of continuity; and (4) Long-term deformation tests (LT) to investigate creep deflections of the composite concrete-CLT floor system considering positive and negative bending influences. Results include overall strength, elastic stiffness values, deformation capacity, slip deformations along the concrete-CLT interface, predicted neutral axis locations in the composite concrete-CLT systems, and connection deformations.
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Cyclic Performance of Connections used in Hybrid Cross-Laminated Timber

https://research.thinkwood.com/en/permalink/catalogue1367
Year of Publication
2017
Topic
Connections
Design and Systems
Material
CLT (Cross-Laminated Timber)
Author
Mahdavifar, Vahid
Organization
Oregon State University
Year of Publication
2017
Country of Publication
United States
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Topic
Connections
Design and Systems
Keywords
North American Market
Density
Low-Grade
High-Grade
Fasteners
Economical
Language
English
Research Status
Complete
Summary
One of the recent additions to the panoply of engineered wood products is cross-laminated timber (CLT). CLT is a prefabricated, large-scale, solid wood panel that consists of multiple layers of lumbers stacked together, with each layer arranged perpendicular to the next layer, glued with structural grade adhesives, and pressed. The use of massive CLT panels in wood construction provides several advantages over the traditional wood frame systems, making it particularly attractive for tall wood building construction. These main advantages are satisfactory distribution of defects, adequate seismic performance, ability to carry large loads, improved strength and stiffness, adequate acceptable fire performance, acceptable acoustic performance, and improved pre-fabrication.It is expected that as the CLT market will continue to mature, more diversified grades and special CLT products will be introduced into the markets. One special CLT product developed in at Oregon State University has been designated as hybrid CLT. Hybrid CLT refers to CLT panels manufactured with layers of high- and low-grade and low-density species, which aims at improving the economic efficiency and sustainability of the CLT industry with focus on the North America market.One of the potential issues with hybrid CLT panel application is related to the unknown performance of the connection systems which are highly dependent on the density of the wood in which the fasteners embed. Most of the existing models that have been developed for estimation of the fasteners capacities in withdrawal and lateral loading scenarios are developed based on the assumption of uniform density profile across the layers to which fasteners penetrate. In a hybrid CLT panel, there is a possibility of a variation in density profile along the panel thickness so that the fasteners can be driven into wood of different densities and driven in directions parallel and perpendicular to grain. Because of the potential variation in density profile in the hybrid CLT, the connection system performance cannot be predicted using design models used for uniform density profile applications similar to the models in National Design Specification (NDS) [1]. Therefore, there is a need for evaluation of connections performance in hybrid layup.The main objective of this work is to characterize the performance of connection systems for hybrid CLT. This is achieved through testing and modeling of single fastener connections and then testing and modeling of the typical connection systems. So, the specific objectives are: (1) evaluate the single fasteners performance to account for density variation and compare the results to a proposed modified model, (2) perform an experimental program to test different connection systems with different hybrid CLT panel layups, (3) develop a numerical algorithm based on the use of meta-heuristics tools to fit the optimal parameters for constitutive models to match the experimental data for the connection systems, (4) obtain the optimal parameters for constitutive models of the connection systems tested.
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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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Behavior of Cross-Laminated Timber Diaphragm Panel-to-Panel Connections with Self-Tapping Screws

https://research.thinkwood.com/en/permalink/catalogue1422
Year of Publication
2017
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Sullivan, Kyle
Organization
Oregon State University
Year of Publication
2017
Country of Publication
United States
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Seismic
Keywords
Lateral Load Resisting System
Monotonic Tests
Cyclic Tests
Strength
Stiffness
Self-Tapping Screws
International Building Code
Language
English
Research Status
Complete
Summary
The goal of this project is to contribute to the development of design values for cross-laminated timber (CLT) diaphragms in the seismic load-resisting system for buildings. Monotonic and cyclic tests to determine strength and stiffness characteristics of 2.44 m (8 ft) long shear connections with common self-tapping screws were performed. Understanding and quantifying the behavior of these shear connections will aid in developing design provisions in the National Design Specification for Wood Construction and the International Building Code so structural engineers can use CLT more confidently in lateral force-resisting systems and extend the heights of wood buildings. Experimental strength-to-design strength ratios were in the range of 2.1 to 8.7. In the ASCE 41 acceptance criteria analysis, the m-factors for the Life Safety performance level in cyclic tests ranged from 1.6 to 1.8 for surface spline connections and from 0.9 to 1.7 for cyclic half-lap connections. The half-lap connections, where screws were installed in withdrawal, shear, shear, and withdrawal, performed exceptionally well with both high, linear-elastic, initial stiffness, and ductile, post-peak behavior.
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Performance Based Tests on Cross Laminated Timber - Concrete Composite Floor Panels

https://research.thinkwood.com/en/permalink/catalogue1423
Year of Publication
2017
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Timber-Concrete Composite
Application
Floors

Utilization of Low-Value Lumber from Small-Diameter Timber Harvested in Pacific Northwest Forest Restoration Programs in Hybrid Cross Laminated Timber (CLT) Core Layers: Technical Feasibility

https://research.thinkwood.com/en/permalink/catalogue1425
Year of Publication
2017
Topic
Design and Systems
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Author
Lawrence, Christina
Organization
Oregon State University
Year of Publication
2017
Country of Publication
United States
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Topic
Design and Systems
Mechanical Properties
Keywords
Small Diameter
Low-Grade
North America
Modulus of Elasticity
Modulus of Rupture
Three Point Bending Test
Rolling Shear Strength
Language
English
Research Status
Complete
Summary
Creating a value-added product using low-grade lumber produced from small-diameter timber would improve the economic balance for forest restoration operation. The general aim of this research was to increase or stimulate markets for wood products utilizing low-value small-diameter material generated in National Forest System restoration programs. Our hypothesis is that low-value lumber cut from small-diameter logs (4”-6” at the small end) could be successfully utilized in core layers of structural cross laminated timber (CLT) panels. However, to be qualified for structural uses, CLT must meet standard minimum bond integrity criteria specified by the North American product standard (ANSI/APA PRG 320-2012), determined through laboratory testing for delamination (=5%) and shear resistance (=80% wood failure). The objective of this project was to determine the feasibility of small-diameter logs harvested from National Forest System restoration programs in 3- and 5ply CLT panels. Adding value to low-value timber harvested from USFS lands by using it within CLT applications is expected to increase profitability of the harvested timber, offsetting costs for the restoration programs. The specific objectives were to: (1) build and test CLT panels utilizing lumber from forest restoration operations in core layers of panels against the certification criteria per PRG 320-2012 to allow low-grade lumber in cores of structural CLT; (2) based on findings, propose respective changes to the current North American standard PRG 320-2012; and (3) investigate the efficiency of the primary processing of small-logs from the thinnings and lamination options with lumber produced from these small logs.
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Utilization of Low-Value Lumber from Small-Diameter Logs Harvested in Pacific Northwest Forest Restoration Programs in Hybrid Cross Laminated Timber (CLT) Core Layers: A Market Response

https://research.thinkwood.com/en/permalink/catalogue1426
Year of Publication
2017
Topic
Mechanical Properties
Market and Adoption
Material
CLT (Cross-Laminated Timber)
Author
Lawrence, Brent
Organization
Oregon State University
Year of Publication
2017
Country of Publication
United States
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Topic
Mechanical Properties
Market and Adoption
Keywords
Small Diameter
Low-Grade
Supply Chain
Manufacturing
Language
English
Research Status
Complete
Summary
This thesis is part of a larger project where lumber from small logs harvested in restoration programs was examined for use in CLT; panels were manufactured utilizing lumber from small logs and the mechanical properties were assessed. While another team focused on mechanical testing to examine the technical viability of this concept according to current manufacturing standards, the objective of this thesis was to assess the practical feasibility of this conception within the supply chain (C. Lawrence, 2017). This research focuses on the Blue Mountains–a region in eastern Oregon. The approach was based on analysis of previous literature, Forest Service Cut & Sold reports, and semi-structured in-person and telephone interviews of federal timberland foresters, sawmill personnel, and management of current and potential cross-laminated timber manufacturers. This research suggests that if the regional supply chain in the Blue Mountains were to process more small diameter logs into lumber, this will increase the available supply of 2x4 and 2x6 dimensions of lumber for use in a variety of different markets rather than for exclusive use in the center layers of cross-laminated timber panels.
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28 records – page 1 of 3.