Common Lateral-Force Resisting Systems in Heavy Timber Structures

Common Lateral-Force Resisting Systems In Heavy Timber Structures Are essential for ensuring the stability and integrity of these structures. They play a crucial role in resisting lateral forces, such as wind and seismic loads, and maintaining the overall safety of the building.

In this article, we will delve into the different types of LFRS commonly employed in heavy timber construction, exploring their advantages and disadvantages, design considerations, construction techniques, and real-world examples.

Lateral-Force Resisting Systems (LFRS) in Heavy Timber Structures

Lateral-force resisting systems (LFRS) are essential components of heavy timber structures, designed to withstand lateral forces such as wind and seismic loads. These systems provide stability and prevent excessive lateral displacement, ensuring the safety and integrity of the structure.

Various types of LFRS are commonly employed in heavy timber construction, each with its advantages and disadvantages. Understanding the different LFRS types and their suitability for specific applications is crucial for engineers and architects involved in heavy timber design.

Types of LFRS in Heavy Timber Structures

• Shear Walls:Shear walls are vertical structural elements that resist lateral forces by transferring them to the foundation. They are typically made of plywood, oriented strand board (OSB), or other shear-resistant materials. Shear walls provide excellent lateral resistance but can be costly and require significant wall space.

• Braced Frames:Braced frames consist of diagonal bracing members that connect vertical and horizontal structural members. They resist lateral forces by forming triangles, which transfer the loads to the foundation. Braced frames are relatively inexpensive and can be used in various configurations, but they can reduce the usable floor space.

• Moment Frames:Moment frames are composed of beams and columns that are connected to resist lateral forces by bending. They transfer the loads to the foundation through moment connections. Moment frames provide good lateral resistance and flexibility in design, but they can be more expensive than other LFRS types.

• Diaphragms:Diaphragms are horizontal structural elements that distribute lateral forces to the vertical LFRS elements. They are typically made of plywood, OSB, or other rigid materials. Diaphragms are essential for transferring lateral forces from the roof and upper floors to the lower levels.

Design Considerations for LFRS in Heavy Timber Structures

When designing LFRS for heavy timber structures, several key considerations must be taken into account to ensure the safety and integrity of the building. These include:

• -*Building design

  The design of the building, including its size, shape, and occupancy, will influence the type of LFRS required. For example, a large, open-plan building will require a different LFRS than a smaller, more compartmentalized building.

-*Site conditions

The site conditions, such as the soil type and seismic activity, can also affect the design of the LFRS. For example, a building located in an area with high seismic activity will require a more robust LFRS than a building located in a less seismically active area.

The key design parameters for LFRS in heavy timber structures include:

• -*Diaphragm strength and stiffness

  The diaphragm is a horizontal structural element that transfers lateral forces to the shear walls or other vertical elements of the LFRS. The strength and stiffness of the diaphragm are critical to the performance of the LFRS.

-*Shear wall strength and stiffness

The shear walls are vertical structural elements that resist lateral forces. The strength and stiffness of the shear walls are critical to the performance of the LFRS.

-*Connection strength and stiffness

The connections between the diaphragm and the shear walls, and between the shear walls and the foundation, are critical to the performance of the LFRS.

The design of the diaphragm is particularly important in heavy timber structures. The diaphragm must be able to transfer lateral forces from the roof and walls to the shear walls without failing. This requires careful attention to the design of the diaphragm connections, as well as the detailing of the diaphragm itself.

Construction Techniques for LFRS in Heavy Timber Structures

Implementing LFRS in heavy timber structures involves various construction techniques, each employing distinct materials and methods. Understanding these techniques is crucial for ensuring the structural integrity and performance of the building.

Materials Used in LFRS Construction

• Heavy Timber:Solid wood members with large cross-sections, typically ranging from 6×6 inches to 12×12 inches or larger.
• Glued-Laminated Timber (Glulam):Engineered wood product made by gluing together layers of smaller timber pieces, resulting in beams with superior strength and stability.
• Cross-Laminated Timber (CLT):A type of engineered wood panel consisting of multiple layers of lumber stacked perpendicularly and glued together, providing excellent strength and stiffness.
• Steel:Used for connecting heavy timber elements, providing reinforcement, and creating shear walls.

Construction Methods

• Timber Framing:Traditional method involving the assembly of heavy timber elements using mortise-and-tenon joints, dowels, or bolts.
• Platform Framing:Construction method where the floor and roof systems are built on top of a platform of horizontal beams.
• Post-and-Beam Construction:Structural system consisting of vertical posts supporting horizontal beams that carry the roof and floor loads.
• Shear Walls:Structural panels made of CLT, plywood, or other materials that resist lateral forces by transferring them to the foundation.
• Moment Frames:Structural systems that resist lateral forces by bending and transferring moments to the foundation.

Quality Control Measures and Best Practices

Ensuring the quality and integrity of LFRS in heavy timber structures is paramount. Proper quality control measures include:

• Inspection of materials for defects and compliance with specifications.
• Proper installation and assembly techniques.
• Adherence to building codes and standards.
• Regular maintenance and inspection to ensure ongoing structural integrity.

By following best practices and employing effective quality control measures, the construction of LFRS in heavy timber structures can be executed to ensure the safety and performance of the building.

Case Studies and Examples of LFRS in Heavy Timber Structures

Real-world applications of heavy timber structures with diverse LFRS showcase their versatility and effectiveness. These case studies provide valuable insights into the design, implementation, and performance of LFRS in heavy timber structures.

The Bow, Calgary, Canada

The Bow, a 58-story skyscraper in Calgary, Alberta, utilizes a moment-resisting frame (MRF) LFRS for lateral force resistance. The MRF consists of heavy timber columns and beams connected with steel moment connections. The structure’s stiffness and strength enable it to withstand high lateral loads due to wind and seismic forces.

Brock Commons Tallwood House, Vancouver, Canada, Common Lateral-Force Resisting Systems In Heavy Timber Structures Are

Brock Commons Tallwood House, the world’s tallest mass timber residential building, employs a cross-laminated timber (CLT) shear wall LFRS. The CLT shear walls, composed of layers of timber glued together, provide exceptional shear resistance and stiffness. This system allows the structure to resist lateral forces efficiently, ensuring stability and occupant safety.

T3 Bayside, Toronto, Canada

T3 Bayside, a 12-story commercial building, utilizes a combination of CLT shear walls and steel moment frames as its LFRS. The CLT shear walls provide lateral resistance in one direction, while the steel moment frames resist forces in the perpendicular direction.

This hybrid system combines the advantages of both LFRS types, enhancing the structure’s overall lateral force resistance capacity.

These case studies demonstrate the successful application of various LFRS in heavy timber structures. They highlight the adaptability and effectiveness of these systems in meeting the demands of different structural designs and site conditions.

Concluding Remarks: Common Lateral-Force Resisting Systems In Heavy Timber Structures Are

In conclusion, the selection and implementation of an appropriate LFRS are critical for the successful design and construction of heavy timber structures. By understanding the various LFRS options available, their design considerations, and construction techniques, engineers and architects can ensure the structural integrity and safety of these buildings while meeting the specific requirements of each project.