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Cross Laminated Timber (CLT) Beams Loaded in Plane: Testing Stiffness and Shear Strength

https://research.thinkwood.com/en/permalink/catalogue2136
Year of Publication
2019
Topic
Mechanical Properties
Design and Systems
Material
CLT (Cross-Laminated Timber)
Application
Beams
Author
Boggian, Francesco
Andreolli, Mauro
Tomasi, Roberto
Organization
University of Trento
Norwegian University of Life Science
Year of Publication
2019
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Design and Systems
Keywords
In-Plane Loading
In-Plane Behaviour
Shear Stresses
Four Point Bending Test
Shear Failure
Modulus of Elasticity
Research Status
Complete
Series
Frontiers in Built Environment
Summary
Cross Laminated Timber (CLT) is a relatively new timber product used in construction that has gained popularity over the last decade. The product itself is constituted by multiple glued layers of juxtaposed boards, usually arranged in an orthogonal direction between one layer and the adjacent ones. This particular structure brings several benefits, such as the possibility to use the same product both for walls and slabs, since it can bear in-plane and out-of-plane loads. However, the mechanical behavior differs from usual timber products, and research is still ongoing to achieve common agreement on standard procedures for testing products and theories for evaluating stresses for safety verifications. This paper focuses on the in-plane shear behavior of CLT and analyzes the existing methods to evaluate shear stresses. An experimental part then presents a four-point bending test of CLT beams with a specific geometry to induce shear failure. Results are reported both for the elastic range test, measuring the Modulus of Elasticity, and for the failure test to investigate shear behavior with regard to different mechanisms. Previously exposed methods are used for the calculation of shear stresses and to analyze the correspondence between them, and the results are then compared with other existing tests and values in literature. A new test setup for future research is eventually proposed.
Online Access
Free
Resource Link
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Design of a novel seismic retrofitting system for RC structures based on asymmetric friction connections and CLT panels

https://research.thinkwood.com/en/permalink/catalogue2912
Year of Publication
2022
Topic
Seismic
Material
CLT (Cross-Laminated Timber)
Author
Aloisoio, Angelo
Boggian, Francesco
Tomasi, Roberto
Organization
Università degli Studi dell’Aquila
Università degli Studi di Trento
Norwegian University of Life Science
Publisher
Elsevier
Year of Publication
2022
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Seismic
Keywords
Friction-based Device
Seismic Protection
Structural Design
Reinforced-concrete Structures
Research Status
Complete
Series
Engineering Structures
Summary
Friction-based dampers are a valid solution for non-invasive seismic retrofitting interventions of existing structures, particularly reinforced-concrete (RC) structures. The design of friction-based dampers is challenging: underestimating the slip force prevents the full use of the potential of the device, which attains the maximum admissible displacement earlier than expected. By contrast, overestimating the slip force may cause delayed triggering of the device when the structure has suffered extensive damage. Therefore, designing the appropriate slip force is an optimization problem. The optimal slip force guarantees the highest inter-story drift reduction. The authors formulated the optimization problem for designing a specific class of friction-based dampers, the asymmetric friction connection (AFC), devised as part of the ongoing multidisciplinary Horizon 2020 research project e-SAFE (Energy and Seismic AFfordable rEnovation solutions). The seismic retrofitting technology involves the external application of modular prefabricated cross-laminated timber (CLT) panels on existing external walls. Friction dampers connect the CLT panels to the beams of two consecutive floors. The friction depends on the mutual sliding of two metal plates, pressed against each other by preloaded bolts. This study determines the optimal slip force, which guarantees the best seismic performance of an RC structural archetype. The authors investigate the nonlinear dynamic response of a coupled mechanical system (RC frame-friction damper) under a set of strong-motion earthquakes, using non-differential hysteresis models calibrated on the experimental cyclic responses. The solution of the optimization leads to the proposal of a preliminary simplified design procedure, useful for practitioners.
Online Access
Free
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The role of the hold-down in the capacity model of LTF and CLT shear walls based on the experimental lateral response

https://research.thinkwood.com/en/permalink/catalogue2849
Year of Publication
2021
Topic
Mechanical Properties
Connections
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Shear Walls
Author
Aloisio, Angelo
Boggian, Francesco
Tomasi, Roberto
Fragiacomo, Massimo
Organization
Università degli Studi dell'Aquila
University of Trento
Norwegian University of Life Science
Publisher
Elsevier
Year of Publication
2021
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Shear Walls
Topic
Mechanical Properties
Connections
Keywords
Hold-Down
Rocking
Cyclic Response
Shear Walls
Light-frame wood
Research Status
Complete
Series
Construction and Building Materials
Summary
Cross Laminated Timber (CLT) and Light Timber Frame (LTF) shear walls are widespread constructive technologies in timber engineering. Despite the intrinsic differences, the lateral response of the two structural systems may be quite similar under specific connection layouts, boundary constraints, and size of the shear walls. This paper compares the experimental cyclic responses of CLT and LTF shear walls characterized by the same size 250×250cm, and loaded according to the EN 12512 protocol. The rigid-body rotation of the shear walls prevails over the deformation and rigid-body translation in the post-elastic displacement range. As a consequence, a capacity model of the two systems based on the sole hold-down response accurately seizes the observed cyclic response, despite ignoring the other resisting contributions. The authors examine the differences exhibited by the CLT and LTF shear walls and the related error corresponding to a capacity model based on the sole hold down restraints. Additionally, it is assessed the overstrength of the CLT panel and LTF sheathing to the shear walls collapse due to the hold-down failure. The estimated overstrength factor is the most meaningful difference between the two structural systems in the considered experimental layouts.
Online Access
Free
Resource Link
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