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Block Shear Failure Mode of Axially Loaded Groups of Screws

https://research.thinkwood.com/en/permalink/catalogue1512
Year of Publication
2016
Topic
Connections
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Solid-sawn Heavy Timber
Author
Mahlknecht, Ursula
Brandner, Reinhard
Augustin, Manfred
Year of Publication
2016
Country of Publication
Austria
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Solid-sawn Heavy Timber
Topic
Connections
Mechanical Properties
Keywords
Self-Tapping Screws
Block Shear Model
Stiffness
Strength
Bending Stresses
Axially-Loaded
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 362-371
Summary
Self-tapping screws are efficient and flexible fasteners, applicable for many types of connections. Investigations on axially loaded groups of screws pointed out, that small spacing between the screws lead to block shear failure mode. So far, block and plug shear failure mode are only analysed for laterally loaded fasteners. Corresponding models cannot be simple transferred to primary axially loaded screws, because of their load insertion continuously along the effective thread featuring a thread-fibre angle perpendicular or with an angle to grain. Results gained by means of two different test configurations, with constant 90° thread-fibre angle but different configurations of group of screws and support conditions are presented. A block shear model is presented, and for mean values for stiffness and strength properties as model parameters are discussed together with values for parameters related to the force distribution over the effective thread length for the first test configuration. Agreement between model and test results was found on a conservative basis. As outlook, considerations of additional bending stresses as well as parameter optimisation are seen as prerequisites and next steps for further model improvement and practicality.
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Development of a Heavy Timber Moment-Resisting Frame with Ductile Steel Links

https://research.thinkwood.com/en/permalink/catalogue1657
Year of Publication
2016
Topic
Connections
Mechanical Properties
Seismic
Material
Solid-sawn Heavy Timber
Application
Frames
Author
Gohlich, Ryan
Erochko, Jeffrey
Year of Publication
2016
Country of Publication
Austria
Format
Conference Paper
Material
Solid-sawn Heavy Timber
Application
Frames
Topic
Connections
Mechanical Properties
Seismic
Keywords
Mid-Rise
Self-Tapping Screws
Moment-Resisting
Strength
Stiffness
Ductility
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 3571-3580
Summary
To improve the seismic performance of mid-rise heavy timber moment-resisting frames, a hybrid timbersteel moment-resisting connection was developed that incorporates specially detailed replaceable steel yielding link elements fastened to timber beams and columns using self-tapping screws (STS). Performance of the connection was verified using four 2/3 scale experimental tests. The connection reached a moment of 142 kN m at the column face while reaching a storey drift angle of 0.05 rad. Two specimens utilizing a dogbone detail in the steel link avoided fracture of the link, while two specimens absent of the dogbone detail underwent brittle failure at 0.05 rad drift. All four test specimens met the acceptance criteria in the AISC 341-10 provisions for steel moment frames. The STS connections exhibited high strength and stiffness, and all timber members and self-tapping screw connections remained elastic. The results of the experimental program indicated that this hybrid connection is capable of achieving a ductility factor similar to that of a steel-only moment-resisting connection. This research suggests that the use of high ductility factors in the design of timber systems that use the proposed hybrid connection would be appropriate, thus lowering seismic design base shears and increasing structure economy.
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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.
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Effects of Climate Change on Structural Behavior of Wood to Wood Connections

https://research.thinkwood.com/en/permalink/catalogue1561
Year of Publication
2016
Topic
Connections
Moisture
Material
Solid-sawn Heavy Timber
Application
Beams
Columns
Author
Jeong, Gi Young
Lee, So Sun
Year of Publication
2016
Country of Publication
Austria
Format
Conference Paper
Material
Solid-sawn Heavy Timber
Application
Beams
Columns
Topic
Connections
Moisture
Keywords
Moisture Content
Dovetail
Beam-to-Beam
Column-to-Column
Structural Behavior
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 1464-1471
Summary
Dovetail connections were applied for connecting column to column, and beam to beam in traditional timber framed buildings. Previous studies were mainly focused on mechanical behaviour of the connection. However, there was a lack of study on the structural behaviour of the connection under different moisture contents. The goal of this study was to analyse the effects of moisture content on swelling behaviour and structural performance of dovetail connection. Different sizes of 120×120, 180×180, 180×240 mm from larix kaempferi and pinus koraiensis were used. Dimensional changes of dovetail connection made from different species showed different trends with an increment of size. The dimensional changes of member of dovetail connection from larix kaempferi were higher than those of dovetail connection made from pinus koraiensis, whereas the dimensional changes of geometric variables of dovetail connection from pinus koraiensis were higher than those of dovetail connection made from larix kaempferi.
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The Heavy Timber Buckling-Restrained Braced Frame as a Solution for Commercial Buildings in Regions of High Seismicity

https://research.thinkwood.com/en/permalink/catalogue1651
Year of Publication
2016
Topic
Seismic
Design and Systems
Material
Solid-sawn Heavy Timber
Application
Wood Building Systems
Author
Blomgren, Hans-Erik
Koppitz, Jan-Peter
Díaz Valdés, Abel
Ko, Eric
Year of Publication
2016
Country of Publication
Austria
Format
Conference Paper
Material
Solid-sawn Heavy Timber
Application
Wood Building Systems
Topic
Seismic
Design and Systems
Keywords
Lateral Load Resisting System
Mid-Rise
High-Rise
US
Building Codes
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 3515-3524
Summary
Timber building construction has been traditionally utilized to reduce inertial demands in high seismic regions. Applications in the United States however, are often limited to low-rise buildings of light-wood construction with distributed load bearing shear walls. Recent advancements in timber technologies are pushing mass timber systems into larger commercial scale markets where steel and concrete systems dominate the landscape. In high seismic regions, mass timber buildings currently lack code-defined lateral force resisting systems. This paper presents a new lateral force resisting system concept, known as the Heavy Timber Buckling-Restrained Braced Frame. The system is conceived, although not limited, for application in mid and high-rise building timber construction, and is inspired by the unbonded steel brace technology today widely spread throughout Japan and the United States. In order to qualify the system for future implementation in building codes, the paper presents results from proof-of-concept component testing of a brace consisting of a steel core and a mechanically laminated glulam casing acting as the bucklingrestraint mechanism. As well, findings from a study for implementation at the building system level is provided in order to assess overall system performance, constructability, and detailing.
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Identifying Incipient Decay in Douglas-fir Bridge Components using X-Ray Computerized Tomography

https://research.thinkwood.com/en/permalink/catalogue2350
Year of Publication
2019
Topic
Design and Systems
Moisture
Serviceability
Material
Glulam (Glue-Laminated Timber)
Solid-sawn Heavy Timber
Application
Bridges and Spans
Author
Senalik, Christopher
Wacker, James
Wang, Xiping
Wu, Xi
Year of Publication
2019
Country of Publication
United States
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Solid-sawn Heavy Timber
Application
Bridges and Spans
Topic
Design and Systems
Moisture
Serviceability
Keywords
X-ray Computerized Tomography
Wood Timber
Brown Rot Fungus
Incipient Decay
Language
English
Conference
International Nondestructive Testing and Evaluation of Wood Symposium
Research Status
Complete
Summary
In this report, wooden members of sizes typically used in bridge construction are examined using x-ray computerized tomography (CT) to determine the presence of internal decay. This report is part of an overall study in which Douglas-fir (Pseudotsuga menziesii) glue-laminated (glulam) beams and solid sawn timbers were inoculated with brown rot fungus, Fomitopsis pinicola, and exposed to aboveground conditions approximately 25 miles (40 km) north of Gulfport, Mississippi, USA. The goal of the overall study is to develop interior decay within the test specimens and then identify and characterize the decay using a variety of nondestructive testing (NDT) techniques. One NDT technique used is x-ray CT. The pixel brightness (PB) of CT scan images is proportional to the specific gravity (SG) at that location; high SG materials appear brighter whereas low SG materials appear darker. The consumption of wood by fungus decreases the wood SG; however, fungal progression takes place in areas where sufficient moisture is present. The presence of moisture increases wood SG as detected by the CT scan, which masks the effect of the fungal decay, which is a common co-occurrence with many NDT techniques. To identify incipient decay, it is necessary to examine the ring structure both within and outside of the area of moisture. Quantifying the extent of the decay requires correlating the PB to known SG values for both dry wood and wood of varying moisture content. In this report, the relationship between wood SG, moisture content, and PB was quantified.
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Multiple Tenons - Experimental Study on Load-Bearing Capacity and Deformation Characteristics

https://research.thinkwood.com/en/permalink/catalogue1530
Year of Publication
2016
Topic
Connections
Mechanical Properties
Material
Solid-sawn Heavy Timber
Author
Claus, Timo
Seim, Werner
Schröder, Bernd
Year of Publication
2016
Country of Publication
Austria
Format
Conference Paper
Material
Solid-sawn Heavy Timber
Topic
Connections
Mechanical Properties
Keywords
Joints
Tenons
Load Bearing Capacity
Deformation
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 733-739
Summary
Modern joinery machines are able to produce precise and complex wood-to-wood connections on a high prefabrication level. For this work, multiple tenon joints were tested to assess the load-bearing capacity and deformation characteristics. Four different geometries of tenon set-ups have been tested. The evaluation of the results shows significantly higher load capacities of multiple tenon joints compared to traditional mortise and tenon geometries. The deformation characteristics show that relocation of loads takes place if the bending capacity of the tenons is guaranteed. Failure of multiple tenon joints occurs with high deformations within the connection. The investigations show the high potential of multiple tenons compared to wood-to-wood connections used currently. Preliminary calculations of mortise and tenon joints show no satisfying accordance with experimental data.
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7 records – page 1 of 1.