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Assessment of Connections in Cross-Laminated Timber Buildings Regarding Structural Robustness

https://research.thinkwood.com/en/permalink/catalogue1948
Year of Publication
2018
Topic
Connections
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Huber, Johannes
Ekevad, Mats
Berg, Sven
Girhammar, Ulf
Year of Publication
2018
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Connections
Mechanical Properties
Keywords
Finite Element Method
Deformation
Multi-Storey
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 20-23, 2018, Seoul, Republic of Korea
Summary
Cross-laminated timber makes timber buildings with an increasing number of storeys achievable. With more storeys, structural robustness needs more attention to make a building survive unforeseen events (e.g. accidents, terrorism) and save lives. For steel and concrete buildings, design methods for robustness focus on connection details. The assessment of joints in cross-laminated timber buildings regarding robustness is rather limited in the literature. The objective of this paper is to conduct an initial assessment of the connectors after the removal of a wall in a platform cross-laminated timber building. We used the finite element method and the component method for the analysis of a case building. The results indicate that the wall-to-wall and the floor-to-floor connectors may fail at low deflection levels leading to high shear loads in the floor panel above the removed wall, which might induce cracking. The removal analysis was only partially completed, but we identified an indication of the deformation behaviour of the case building. Testing and refined modelling of the connections is needed in the future to verify the results. This study may facilitate future investigations regarding robustness of multi-storey cross-laminated timber buildings.
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Finite element analysis of alternative load paths to prevent disproportionate collapse in platform-type CLT floor systems

https://research.thinkwood.com/en/permalink/catalogue2901
Year of Publication
2021
Topic
Design and Systems
Material
CLT (Cross-Laminated Timber)
Application
Floors
Author
Huber, Johannes
Bita, Hercend
Tannert, Thomas
Berg, Sven
Organization
Luleå University of Technology
University of Northern British Columbia
Publisher
Elsevier
Year of Publication
2021
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Floors
Topic
Design and Systems
Keywords
Mass Timber
Structural Robustness
High Fidelity Model
Progressive Collapse
Structural Integrity
Component Model
Research Status
Complete
Series
Engineering Structures
Summary
Multi-storey buildings require mitigation of consequences of unexpected or accidental events, to prevent disproportionate collapse after an initial damage. Cross-laminated timber (CLT) in platform-type construction is increasingly used for multi-storey buildings, however, the collapse behaviour and alternative load paths (ALPs) are not fully understood. A 3D non-linear component-based finite element model was developed for a platform-type CLT floor system to study the ALPs after an internal wall loss, in a pushdown analysis. The model, which accounted for connection failure, timber crushing and large displacements, was calibrated to experimental results and then adapted for boundary conditions corresponding to typical residential and office buildings. Subsequently, five parameters (floor span, connection type, vertical location of the floor, tying level, horizontal wall stiffness) were varied, to study their effects on the ALPs in 80 models. The results showed that three ALPs occurred, of which catenary action was the most dominant. Collapse resistance was mainly affected by the floor span, followed by the axial strength, stiffness and ductility of the floor-to-floor connection, the weight of the level above and the floor panel thickness. This study provides an approach to model ALPs in a platform-type CLT floor system to design disproportionate collapse resistant multi-storey CLT buildings.
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Free
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Finite Element Analysis of Bending Stiffness for Cross-Laminated Timber with Varying Board Width

https://research.thinkwood.com/en/permalink/catalogue2455
Year of Publication
2019
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Author
Berg, Sven
Turesson, Jonas
Ekevad, Mats
Huber, Johannes
Organization
Luleå University of Technolog
Publisher
Taylor&Francis Online
Year of Publication
2019
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Mechanical Properties
Keywords
Finite Element Analysis
Board Width
Out-of-Plane Load
Research Status
Complete
Series
Wood Material Science & Engineering
Summary
Cross laminated timber (CLT) is a wood panelling building system that is used in construction, e.g. for floors, walls and beams. Because of the increased use of CLT, it is important to have accurate simulation models. CLT systems are simulated with one-dimensional and two-dimensional (2D) methods because they are fast and deliver practical results. However, because non-edge-glued panels cannot be modelled under 2D, these results may differ from more accurate calculations in three dimensions (3D). In this investigation, CLT panels with different width-to-thickness ratios for the boards have been simulated using the finite element method. The size of the CLT-panels was 3.0 m × 3.9 m and they had three and five laminate layers oriented 0°–90°–0° and 0°–90°–0°–90°–0°. The thicknesses of the boards were 33.33, 40.0, and 46.5 mm. The CLT panel deformation was compared by using a distributed out-of-plane load. Results showed that panels with narrow boards were less stiff than wide boards for the four-sided support setup. The results also showed that 2D models underestimate the displacement when compared to 3D models. By adjusting the stiffness factor k88, the 2D model displacement became more comparable to the 3D model.
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Modelling Alternative Load Paths in Platform-Framed CLT Buildings: A Finite Element Approach

https://research.thinkwood.com/en/permalink/catalogue2113
Year of Publication
2019
Topic
Design and Systems
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems

Structural Robustness and Timber Buildings - A Review

https://research.thinkwood.com/en/permalink/catalogue2173
Year of Publication
2019
Topic
Design and Systems
Material
Glulam (Glue-Laminated Timber)
Light Frame (Lumber+Panels)
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Huber, Johannes
Ekevad, Mats
Girhammar, Ulf
Berg, Sven
Organization
Luleå University of Technology
Publisher
Taylor&Francis Online
Year of Publication
2019
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Light Frame (Lumber+Panels)
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Design and Systems
Keywords
Robustness
Disproportionate Collapse
Progressive Collapse
Alternative Load Path
Damage Tolerance
Research Status
Complete
Series
Wood Material Science & Engineering
Summary
Timber buildings are increasing in their dimensions. Structural robustness is imperative for all buildings and specifically important for tall buildings. Lives can be saved if disproportionate collapse can be avoided after a catastrophic event (e.g. accident, terrorism). The literature about robustness is comprehensive concerning concrete and steel buildings, but is rather limited regarding timber. This paper reviews robustness in general and robustness of timber buildings in particular. Robustness is an intrinsic structural property, enhancing global tolerance to local failures, regardless of the cause. A deterministic approach to assess robustness is to remove certain load-bearing elements from the structure and compare the consequences to given limits. Design methods for robustness may be direct by assessing effects of local failure, or indirect by following guidelines. For robust timber buildings, the connections are the key aspects. Usually, metal connectors may provide the required joint ductility. For robust light timber-frame construction, rim beams may be designed. For timber posts and beams and cross laminated timber, guidance regarding robustness is scarce, but in some aspects they seem to be similar to steel frames and precast concrete. Future research should assess the capacity of connections, and evaluate the adequacy of seismic connectors for robust timber buildings.
Online Access
Free
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