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Nested Buildings: An Innovative Strategy for the Integrated Seismic and Energy Retrofit of Existing Masonry Buildings with CLT Panels

https://research.thinkwood.com/en/permalink/catalogue2770
Year of Publication
2021
Topic
Design and Systems
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Hybrid Building Systems
Author
Valluzzi, Maria Rosa
Saler, Elisa
Vignato, Alberto
Salvalaggio, Matteo
Croatto, Giorgio
Dorigatti, Giorgia
Turrini, Umberto
Publisher
MDPI
Year of Publication
2021
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Hybrid Building Systems
Topic
Design and Systems
Seismic
Keywords
Nested Buildings
Seismic Retrofitting
Energy Efficiency
Integrated Intervention
Built Heritage
Masonry Buildings
Panels
Hybrid Structures
Italy
Language
English
Research Status
Complete
Series
Sustainability
Summary
The Italian building heritage is aged and inadequate to the high-performance levels required nowadays in terms of energy efficiency and seismic response. Innovative techniques are generating a strong interest, especially in terms of multi-level approaches and solution optimizations. Among these, Nested Buildings, an integrated intervention approach which preserves the external existing structure and provides a new structural system inside, aim at improving both energy and structural performances. The research presented hereinafter focuses on the strengthening of unreinforced masonry (URM) buildings with cross-laminated timber (CLT) panels, thanks to their lightweight, high stiffness, and good hygrothermal characteristics. The improvement of the hygrothermal performance was investigated through a 2D-model analyzed in the dynamic regime, which showed a general decreasing in the overall thermal transmittance for the retrofitted configurations. Then, to evaluate the seismic behavior of the coupled system, a parametric linear static analysis was implemented for both in-plane and out-of-plane directions, considering various masonry types and connector spacings. Results showed the efficiency of the intervention to improve the in-plane response of walls, thus validating possible applications to existing URM buildings, where local overturning mechanisms are prevented by either sufficient construction details or specific solutions. View Full-Text
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Cross Laminated Timber Shear Wall Connections for Seismic Applications

https://research.thinkwood.com/en/permalink/catalogue2405
Year of Publication
2020
Topic
Connections
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Walls
Author
Falk, Michael
Publisher
Kansas State University
Year of Publication
2020
Country of Publication
United States
Format
Report
Material
CLT (Cross-Laminated Timber)
Application
Walls
Topic
Connections
Seismic
Keywords
Panels
Earthquake
Rocking Walls
Shear Walls
Language
English
Research Status
Complete
Online Access
Free
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Cross Laminated Timber Shear Wall Connections for Seismic Applications

https://research.thinkwood.com/en/permalink/catalogue2406
Year of Publication
2020
Topic
Connections
Seismic
Material
CLT (Cross-Laminated Timber)
Application
Walls
Author
Falk, Michael
Publisher
Kansas State University
Year of Publication
2020
Country of Publication
United States
Format
Report
Material
CLT (Cross-Laminated Timber)
Application
Walls
Topic
Connections
Seismic
Keywords
Panels
Earthquake
Rocking Walls
Shear Walls
Language
English
Research Status
Complete
Online Access
Free
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Fire Tests of South African Cross-laminated Timber Wall Panels: Fire Ratings, Charring Rates, and Delamination

https://research.thinkwood.com/en/permalink/catalogue2442
Year of Publication
2020
Topic
Fire
Material
CLT (Cross-Laminated Timber)
Application
Walls
Author
van der Westhuyzen, S.
Walls, R.
de Koker, N.
Publisher
Scientific Elecronic Library Online (SciELO) South Africa
Year of Publication
2020
Country of Publication
South Africa
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Walls
Topic
Fire
Keywords
Structural Fire Engineering
Charring Rate
Delamination
Panels
Pine
Eucalyptus
Language
English
Research Status
Complete
Series
Journal of the South African Institution of Civil Engineering
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Bending, Shear, and Compressive Properties of Three- and Five-Layer Cross-Laminated Timber Fabricated with Black Spruce

https://research.thinkwood.com/en/permalink/catalogue2589
Year of Publication
2020
Topic
Design and Systems
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Author
He, Minjuan
Sun, Xiaofeng
Li, Zheng
Feng, Wei
Publisher
SpringerOpen
Year of Publication
2020
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Design and Systems
Mechanical Properties
Keywords
Black Spruce
Panels
Bending
Thickness
Language
English
Research Status
Complete
Series
Journal of Wood Science
Summary
Cross-laminated timber (CLT) is an innovative engineering wood product made by gluing layers of solid-sawn lumber at perpendicular angles. The commonly used wood species for CLT manufacturing include spruce-pine-fir (SPF), douglas fir-larch, and southern pine lumber. With the hope of broadening the wood species for CLT manufacturing, the purposes of this study include evaluating the mechanical properties of black spruce CLT and analyzing the influence of CLT thickness on its bending or shear properties. In this paper, bending, shear, and compressive tests were conducted respectively on 3-layer CLT panels with a thickness of 105 mm and on 5-layer CLT panels with a thickness of 155 mm, both of which were fabricated with No. 2-grade Canadian black spruce. Their bending or shear resisting properties as well as the failure modes were analyzed. Furthermore, comparison of mechanical properties was conducted between the black spruce CLT panels and the CLT panels fabricated with some other common wood species. Finally, for both the CLT bending panels and the CLT shear panels, their numerical models were developed and calibrated with the experimental results. For the CLT bending panels, results show that increasing the CLT thickness whilst maintaining identical span-to-thickness ratios can even slightly reduce the characteristic bending strength of the black spruce CLT. For the CLT shear panels, results show that increasing the CLT thickness whilst maintaining identical span-to-thickness ratios has little enhancement on their characteristic shear strength. For the CLT bending panels, their effective bending stiffness based on the Shear Analogy theory can be used as a more accurate prediction on their experiment-based global bending stiffness. The model of the CLT bending specimens is capable of predicting their bending properties; whereas, the model of the CLT shear specimens would underestimate their ultimate shear resisting capacity due to the absence of the rolling shear mechanism in the model, although the elastic stiffness can be predicted accurately. Overall, it is attested that the black spruce CLT can provide ideal bending or shear properties, which can be comparable to those of the CLT fabricated with other commonly used wood species. Besides, further efforts should focus on developing a numerical model that can consider the influence of the rolling shear mechanism.
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Flexural Performance of Novel Nail-Cross-Laminated Timber Composite Panels

https://research.thinkwood.com/en/permalink/catalogue2649
Year of Publication
2020
Topic
Mechanical Properties
Design and Systems
Material
CLT (Cross-Laminated Timber)
Author
Zhang, Yannian
Nehdi, Moncef
Gao, Xiaohan
Zhang, Lei
Publisher
MDPI
Year of Publication
2020
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Mechanical Properties
Design and Systems
Keywords
Panels
Flexural Performance
Nails
Bending
Model
Prediction
Fracture
Language
English
Research Status
Complete
Series
Applied Sciences
Summary
Cross-laminated timber (CLT) is an innovative wood panel composite that has been attracting growing interest worldwide. Apart from its economic benefits, CLT takes full advantage of both the tensile strength parallel to the wood grain and its compressive strength perpendicular to the grain, which enhances the load bearing capacity of the composite. However, traditional CLT panels are made with glue, which can expire and lose effectiveness over time, compromising the CLT panel mechanical strength. To mitigate such shortcomings of conventional CLT panels, we pioneer herein nail-cross-laminated timber (NCLT) panels with more reliable connection system. This study investigates the flexural performance of NCLT panels made with different types of nails and explores the effects of key design parameters including the nail incidence angle, nail type, total number of nails, and number of layers. Results show that NCLT panels have better flexural performance than traditional CLT panels. The failure mode of NCLT panels depends on the nail angle, nail type, and quantity of nails. A modified formula for predicting the flexural bearing capacity of NCLT panels was proposed and proven accurate. The findings could blaze the trail for potential applications of NCLT panels as a sustainable and resilient construction composite for lightweight structures.
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Operational Performance of Cross Laminated Timber: Brock Commons Tallwood House

https://research.thinkwood.com/en/permalink/catalogue2679
Year of Publication
2020
Topic
Moisture
Serviceability
Material
CLT (Cross-Laminated Timber)
Application
Columns
Walls
Organization
UBC Sustainability Initiative
Year of Publication
2020
Country of Publication
Canada
Format
Report
Material
CLT (Cross-Laminated Timber)
Application
Columns
Walls
Topic
Moisture
Serviceability
Keywords
Moisture Content
Moisture Performance
Monitoring
Vertical Movement
Panels
Language
English
Research Status
Complete
Summary
The Tallwood House project was intended to advance the design and manufacture of mass timber products in Canada and demonstrate that mass timber is a viable structural option for mid-rise and high-rise buildings. The use of mass timber and engineered wood products in high-rise construction is becoming more common around the world leading to a growing interest in the performance of mass timber over time. This report describes the performance of the mass timber structure in Tallwood House, between September 2017 and August 2019, based on measurements of the moisture content in the prefabricated CLT floor panels and the displacement of the vertical structural system. It is intended to initiate discussions on the performance of mass timber structure elements during building occupancy and lead to further research that can explore the influential factors.
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Effects of Heavy Topping on Vibrational Performance of Cross-Laminated Timber Floor Systems

https://research.thinkwood.com/en/permalink/catalogue2708
Year of Publication
2020
Topic
Acoustics and Vibration
Material
CLT (Cross-Laminated Timber)
Application
Floors
Author
Schwendy, Benjamin
Publisher
Clemson University
Year of Publication
2020
Country of Publication
United States
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Application
Floors
Topic
Acoustics and Vibration
Keywords
Vibration Serviceability
Concrete Topping
Panels
Insulation
Language
English
Research Status
Complete
Summary
Cross-Laminated Timber (CLT) is gaining momentum as a competitor to steel and concrete in the construction industry. However, with CLT being relatively new to North America, it is being held back from realizing its full potential by a lack of research in various areas, such as vibration serviceability. This has resulted in vague design guidelines, leading to either overly conservative designs, hurting profit margins, or leading to overly lenient designs, resulting in occupancy discomfort. Eliminating these design inefficiencies is paramount to expanding the use of CLT and creating a more sustainable construction industry. This thesis focuses on the effect of a heavy topping, in this case 2" of concrete over a layer of rigid insulation, on a CLT floor. To this end, modal analysis was performed on two spans of three CLT panels in the Andy Quattlebaum Outdoor Education Center at Clemson University. By performing a series of instrumented heel-drop tests with a roving grid of accelerometers, the natural frequencies, mode shapes, frequency response functions, and damping coefficients were determined. By comparing the results to several different numerical models, the most appropriate model was selected for use in future design. In addition, a walking excitation test was performed to calculate the root mean square acceleration of the floor for comparison to current design standards. This study found that, with a layer of rigid insulation separating the topping and the panel, the system behaved predictably like a non-composite system. The resultant mode shapes also verified that the boundary conditions behaved very close to “hinged” and showed that the combination of the surface splines and the continuous topping provide significant transverse continuity in terms of response to vibrations. Lastly, the results of the walking excitation test showed that, with some further study, the current design standards for steel vibration serviceability can be applied to great effect to CLT systems.
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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
Language
English
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.
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Dynamic Response of Cross Laminated Timber Floors Subject to Internal Loads

https://research.thinkwood.com/en/permalink/catalogue2716
Year of Publication
2020
Topic
Design and Systems
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Floors
Author
Skoglund, Jacob
Publisher
Lund University
Year of Publication
2020
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Application
Floors
Topic
Design and Systems
Mechanical Properties
Keywords
Internal Loads
Finite Element Method (FEM)
Panels
Seven-Layer Model
Modal Analysis
3D Model
2D Model
Language
English
Research Status
Complete
Summary
The deregulation of timber for use in large scale constructions has seen the addition of new innovative timber-based products to a category of products referred to as engineered wood products. A now well established addition to these products is cross laminated timber, or CLT for short. CLT products use a form of orthogonal layering, where several parallel wooden boards are arranged in a number of layers, each layer being orthogonal to the previous. The use of orthogonal layering allows for increased stiffness in the two plane directions, resulting in a lightweight construction product with high load bearing capacity and stiffness. To evaluate the dynamic behaviour of structures, engineers commonly apply the finite element method, where a system of equations are solved numerically. Given a sufficient amount of computational power and time, the finite element method can help to solve most dynamical problems. For sufficiently large or complex structures the amount of resources needed may be outside the scope of possibility or feasibility for many. Therefore, evaluating the usage of certain design simplifications, such as omitting to models aspects of the geometry, or alternative forms of analysis for CLT panels may help to reduce the time and resources required for an analysis. In this Master's dissertation, a seven-layer CLT-panel has been created. In the model, each individual board and the gaps between the boards are modelled. The seven-layer model is used as a reference to evaluate the possibility of using less detailed alternative models. The alternative models are created as a layered 3D model and a composite 2D model, both models omit the modelling of the individual laminations, resulting in the layers being solid. The results show small errors for the alternative models when using modal analysis. Concluding that the modal behaviour and dynamic response of a CLT panel can be evaluated using a composite 2D model or a less-detailed layered 3D model. This significantly reduces the amount of time and computational power needed for an analysis, and clearly indicates the benefit of using alternative less detailed models.
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72 records – page 1 of 8.