CONNECTIONS IN CROSS LAMINATED TIMBER

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CONNECTING CLT PANELS RIGHT!

Cross Laminated Timber has the ability to resist splitting due to X-lamination. This is however achieved when the right connections are used, with the right bolt fixed into its corresponding nut. If panels are poorly joined, slight shear deformations (panel deflections) are likely to occur as a result of the deformation in the joints. In case of multi-panel walls, deformations in the step joints might have significant contribution to the overall wall deflection.
CLT wall panels behave as rigid bodies when subjected to seismic loads. CLT structures have an adequate seismic performance when nails or screws are used with the steel brackets. Therefore, the use of hold-downs with nails on each end of the wall improves its seismic performance but how this is done matters a lot. Every connection type differs according to the building sections in question such as:

• Wall to concrete connections
• Wall to wall connections
• Wall to floor connections
• Floor to floor connections
• Wall to slab/ceiling connections
• Beam to column/wall connections
• Wall to roof connections

 

 

WALL TO CONCRETE FLOOR CONNECTIONS

In connecting CLT wall panels to concrete foundations, exterior metal plates and brackets are commonly due to their simplicity in terms of installation.
Direct contact between the concrete foundation and CLT panel should be avoided in all cases by using treated wood timber or SCL sill plate (or bottom plate)

1. Use of concealed metal plates
These are hidden metal plates placed at the bottom of the CLT but require that the timber panel has grooves to conceal the metal plates. Fasteners that can be drilled through both the metal and wood should be used.

2. Use of exposed steel plates
When connections are established from outside, a typical metal plate is used. The exposed metal plates and fasteners must be protected against corrosion as this would weaken the joints or rather, one can use galvanized/stainless steel. However, when access is provided from inside the building and where a concrete slab exists, the metal brackets. Lag screws or powder-actuated fasteners are then used to connect the metal plate to the concrete footing/slab, while lag screws or self-tapping screws are used to connect the plate to the CLT panel.

  

3. Use of wooden profiles
Here, the wooden profiles are attached to CLT panels with wood screws or self-tapping screws. These should be produced at the CLT plant for an effective connection. These can take several forms to provide additional protection and reinforcement to the bottom edge of the panel. They can also be used for wall-to-wall or floor-to-wall connections.

NOTE:  It is important that connection details be designed by the manufacturer to prevent potential moisture penetration between the metal plates and the CLT wall as water may get trapped and cause potential decay of the wood.

 

 

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Posted on: January 12th, 2022 by London Building Contractors No Comments

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