Structural analysis of CLT walls in façades of a multistory building

Master thesis (2023)

Authors

P. Mol Civil Engineering & Geosciences

Contributors

J.W.G. van de Kuilen Bio-based Structures & Materials - CEG (mentor)
G.J.P. Ravenshorst Bio-based Structures & Materials - CEG (graduation committee member)
H. Alkisaei Applied Mechanics - CEG (coach)
Faculty
Civil Engineering & Geosciences, Civil Engineering & Geosciences
Copyright: © 2023 Pim Mol
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Published Date

01-02-2023

Language

English

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Faculty

Civil Engineering & Geosciences

Abstract

This thesis report provides an analysis of the structural behavior of façades made of CLT panels with openings. These openings will have a significant influence on the transfer of forces in the panels, as well as the stiffness of the façade. The connections required to transfer the forces between the panels are designed. Deformations of the connections introduce addition deformation of the façade itself. The components that influence the force transfer and deformation of the façade have been identified in this research. Their contributions have been investigated. The theoretical calculations have been compared to computer results. The resulting conclusions aid designers in an early design phase regarding the feasibility of a CLT façade structure.

The main focus of the research has been on the mechanical fastener connections that are required for the CLT façades. The research question is stated as:

“What is the influence of mechanical fastener connections on the strength and stiffness of CLT façades that function as the main stability system?”

The research started with the goal to find the limitations of CLT façades for multi-story timber buildings. In order to find these limitations, a complete understanding of the structural behavior of the façade was required. Since connections were found to be of great influence the research focused on this topic.

The structural behavior of the façade was defined as the top deformation of the structure and the force transfer and resulting stresses in the panels. The dynamic response of the structure has not been analyzed.
Seven components were identified that influence the stiffness and force transfer in the structure.

Bending of the façade
Shearing of the façade
Bending of lintels
Bending of piers
Sliding of connections
Rocking of connections
Additional bending deformations due to connections

Computer models were used to verify the overall behavior of the façade as found with the theory. The computer model did not verify each individual component.

Peak shear forces in the CLT panels near the corners of openings determine the required panel thickness.
When these shear forces are reduced (for example by applying a concrete core in the structure) the required panel thickness can be reduced.

Top deformations of a façade with a width of 20 meter limit the maximum height to 45 to 55 meter, depending on the connection stiffness.

The main contributor to the top deformation is the connection stiffness of the connections between the vertical edges of the CLT panels. These influence the collaboration between the panels, hence significantly affect the bending stiffness and corresponding bending forces in the panels.

The lintels of the façade panels highly influence the load distribution in the façade. There is no accurate method to calculate this influence on the load distribution.