CLT Lateral Design (Seismic & Wind)

Summary

This video discusses the performance of Cross-Laminated Timber (CLT) in seismic and wind load testing, based on research over the past decade. It covers the testing of various connections, such as spiral and ring nails, and their impact on CLT wall performance under lateral loads. Key findings suggest that spiral nails offer better performance, and that introducing half-lap joints can enhance seismic energy dissipation. Additionally, it explores the importance of using innovative screws and capacity-based design for CLT structures in earthquake-prone regions. CLT's potential for mid-rise and large public buildings is highlighted, along with the ongoing development of seismic design factors for CLT structures.

Takeaways

• 😀 CLT (Cross-Laminated Timber) has been used for nearly 20 years, but its performance under seismic and wind loads has only been studied in the last decade.
• 😀 FP Innovations conducted tests on CLT connections using various brackets and screws to determine the best configurations for seismic performance.
• 😀 Spiral nails are better than ring nails for CLT connections in high seismic areas because they don't cause wood chunks to be pulled out during testing.
• 😀 Screws with slender diameters are also a viable option for CLT, offering good seismic performance, though they are slightly less ductile than spiral nails.
• 😀 CLT walls with brackets and holds at the ends of the walls exhibited the best seismic performance in testing.
• 😀 For longer CLT walls, it is recommended to break them into segments using half lap joints, which improve wall ductility and seismic energy dissipation.
• 😀 Innovative screw types, like SFS WTT screws, were tested, but screws placed at 45-degree angles failed in tension and didn't provide sufficient strength or energy dissipation.
• 😀 Shake table tests on CLT buildings showed they could withstand earthquakes with minimal damage to both structure and interior contents.
• 😀 CLT is a good fit for mid-rise buildings (4 stories and above) and large industrial or public buildings due to its seismic performance.
• 😀 A capacity-based design method is recommended for designing CLT structures, with fuses at shear wall connections to ensure energy dissipation during earthquakes.

Q & A

What is the focus of the research on CLT (Cross-Laminated Timber)?

The research focuses on testing the performance of CLT under lateral loads, such as seismic and wind loads, and evaluating different connection methods and materials used in CLT wall systems.

What types of connectors are commonly used in CLT walls in Europe and North America?

In Europe, annual ring nails are commonly used, while in North America, spiral nails are more common for CLT wall connections.

What did the research find about the performance of spiral nails compared to ring nails in CLT walls?

The research found that spiral nails perform better than ring nails because ring nails tend to pull out from the wall, damaging the wood by taking chunks out, while spiral nails provide better structural performance, especially in high seismic areas.

How do slender diameter screws compare to spiral nails for CLT wall connections?

Slender diameter screws are less ductile than spiral nails but still provide adequate seismic performance. However, spiral nails tend to perform better in terms of flexibility and energy dissipation.

What was discovered about the performance of CLT walls with brackets and holds at the ends?

CLT walls with brackets and holds at the ends exhibited the best performance among the various wall configurations tested, showing superior resilience to lateral loads.

Why is it beneficial to break longer CLT walls into multiple segments?

Breaking longer CLT walls into multiple segments using half lap joints increases the wall's ductility and enhances seismic energy dissipation, which is crucial during an earthquake.

What type of screws were tested, and what was their outcome in wall connections?

Innovative screws like SFS WTT screws were tested. However, screws placed at a 45-degree angle, where the wall is held to the ceiling, failed in tension, providing minimal strength and energy dissipation during testing.

What did the research from the Italian Tree and Timber Research Institute show about CLT buildings' earthquake resistance?

The research showed that CLT buildings, including two-story and seven-story structures, performed well under multiple earthquake motions, with minimal damage to both the building and its contents.

What is the recommended use for CLT in terms of building types and seismic design?

CLT is recommended for mid-rise buildings (four stories or more), as well as large industrial or public buildings. It is also suggested to use a capacity-based design method for CLT structures in seismic regions.

What is the role of the 'R factor' in seismic design for CLT structures?

The 'R factor' in seismic design reduces the seismic design load by accounting for the non-linear flexibility of the CLT structure, which helps dissipate seismic energy and reduce the forces on the building during an earthquake.