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Diaphragm shear and diagonal compression testing of cross-laminated timber

https://research.thinkwood.com/en/permalink/catalogue2858
Year of Publication
2021
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Floors
Walls
Author
Sharifi, Jonas
Sharifi, Zahra
Berg, Sven
Ekevad, Mats
Organization
Luleå University of Technology
Publisher
Springer
Year of Publication
2021
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Floors
Walls
Topic
Mechanical Properties
Keywords
Diagonal Compression Test
Diaphragm Shear Test
Shear Modulus
Research Status
Complete
Series
SN Applied Sciences
Summary
To learn the characteristics of a cross-laminated timber (CLT) panel, it is crucial to perform experimental tests. This study presents two experimental test methods to measure the in-plane shear modulus of CLT panels. This characteristic can be measured by multiple methods such as the picture frame test, the diagonal compression test, and the diaphragm shear test. In this study, the same CLT panels are tested and evaluated in the diaphragm shear test and the diagonal compression test to see if more reliable results can be achieved from the diaphragm shear test. This evaluation is done by experimental tests and finite element simulations. The theoretical pure shear simulation is used as a reference case. Finite element simulations are made for both edge glued and non-edge glued CLT panels. Nine CLT panels are tested in the diaphragm shear test and the diagonal compression test. During ideal conditions (uniform material properties and contact conditions), all three simulated methods result in an almost equal shear modulus. During the experimental testing, the diagonal compression test gives more coherent results with the expected shear modulus based on finite element simulations. Based on the diaphragm shear test results, the CLT panels behave like edge glued, but this situation is dismissed. However, during ideal conditions, the diaphragm shear test is seen as a more reliable method due to the higher proportion of shear in the measured area.
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Influence of laminate direction and glue area on in-plane shear modulus of cross-laminated timber

https://research.thinkwood.com/en/permalink/catalogue2857
Year of Publication
2020
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Floors
Walls
Author
Turesson, Jonas
Sharifi, Zahra
Berg, Sven
Ekevad, Mats
Organization
Luleå University of Technology
Publisher
Springer
Year of Publication
2020
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Floors
Walls
Topic
Mechanical Properties
Keywords
Diagonal Compression Test
Laminate Direction
Shear Modulus
Research Status
Complete
Series
SN Applied Sciences
Summary
The use of cross-laminated timber (CLT) in constructing tall buildings has increased. So, it has become crucial to get a higher in-plane stiffness in CLT panels. One way of increasing the shear modulus, G, for CLT panels can be by alternating the layers to other angles than the traditional 0° and 90°. The diagonal compression test can be used to measure the shear stiffness from which G is calculated. A general equation for calculating the G value for the CLT panels tested in the diagonal compression test was established and verified by tests, finite element simulations and external data. The equation was created from finite element simulations of full-scale CLT walls. By this equation, the influence on the G value was a factor of 2.8 and 2.0 by alternating the main laminate direction of the mid layer from the traditional 90° to 45° and 30°, respectively. From practical tests, these increases were measured to 2.9 and 1.8, respectively. Another influence on the G value was studied by the reduction of the glue area between the layers. It was shown that the pattern of the contact area was more important than the size of the contact area.
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Free
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Influence of Openings on the Shear Strength and Stiffness of Cross Laminated Timber (CLT) Panels

https://research.thinkwood.com/en/permalink/catalogue2710
Year of Publication
2020
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Walls
Shear Walls
Author
Aljuhmani, Ahmad
Ogasawawra, A.
Atsuzawa, E.
Alwashali, Hamood
Shegay, A. V.
Tafheem, Zasiah
Maeda, Masaki
Year of Publication
2020
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Walls
Shear Walls
Topic
Mechanical Properties
Keywords
Diagonal Compression Test
Openings
Lateral Strength
In-Plane Shear Stiffness
Panels
Conference
World Conference on Earthquake Engineering
Research Status
Complete
Summary
In the last decade, cross laminated timber (CLT) has been receiving increasing attention as a promising construction material for multi-storey structures in areas of high seismicity. In Japan, application of CLT in building construction is still relatively new; however, there is increasing interest in CLT from researchers as well as construction companies. Furthermore, the Japanese government is providing construction cost subsidies for new CLT structures as it is a carbon neutral and sustainable material. The high shear and compressive strength of CLT makes it a good candidate for use as shear walls in mid-rise buildings. One important aspect of CLT walls, and one that is presently poorly understood, is the influence of openings on the shear carrying capacity. Openings are often necessary in CLT panels either in form of windows, doors, lift shaft openings or installation of building services. Concerning this aspect, the code regulations in Japan are relatively strict, such that if openings exceeded certain prescribed limits, the entire CLT panel is considered as a non-structural element, and its contribution to lateral strength is totally ignored. Furthermore, as the maximum opening size is usually governed by edge distance constraints, the size of openings that designers can use is inevitably limited by the standard sizes supplied by the manufacturers. As a result, designers are obligated to adopt very small opening size. This is thought to be a very conservative approach. The main purpose of this paper is to experimentally evaluate the influence of openings on seismic capacity; strength and stiffness reduction, as well as failure mode with changing opening size and opening aspect ratio. In addition, check the validity of the Japanese code regulations with regards to openings in CLT panels. In this study, six 5-layer CLT panels containing different openings were tested. The parameters considered include the size and layout of the opening. The panels were specifically designed with openings that would render them ineffective in resisting lateral loads according to the Japanese standard. However, in addition to the six panels, one panel without openings and one panel with openings that meet the Japanese standard was designed. All the CLT panels were tested in uniaxial diagonal compression in order to simulate pure shear loading. The CLT panels and the loading setup were designed such that the resulting failure mode will be governed by a shear mechanism. The main focus of the experiment was to relate the deterioration of the lateral strength and stiffness of the panels to the size and layout of the opening. The results showed that the panels with openings with the same area have relatively different failure direction and reduction factors for panel shear strength and stiffness, and that is due to the shear weak and strong direction that CLT panels have. Also, the effect of openings on the reduction of stiffness for CLT panels was found to be greater than their effect on the reduction of shear strength. The prescribed equation in the Japanese CLT Guidebook underpredicts stiffness reduction, and has discrepancies with regard to strength as the difference of panel strengths in weak and strong directions are not considered.
Online Access
Free
Resource Link
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In-plane Shear Modulus of Cross-laminated Timber by Diagonal Compression Test

https://research.thinkwood.com/en/permalink/catalogue2420
Year of Publication
2019
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Walls
Beams
Floors

Picture Frame and Diagonal Compression Testing of Cross-laminated Timber

https://research.thinkwood.com/en/permalink/catalogue2402
Year of Publication
2019
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Walls
Wood Building Systems
Floors