Timber is connected through various fasteners and specialized connection systems designed to join wood members securely and transfer structural loads within structures ranging from simple framing to complex heavy timber construction.
Timber connections utilize a range of methods, primarily falling into two categories: those using fasteners inserted directly into the wood and those employing connectors or systems that facilitate or enhance the joint.
Common Timber Connection Fasteners
These are individual elements driven or screwed directly into the timber members being joined. They are fundamental to many types of wood connections.
- Nails: Simple, widely used fasteners driven into wood. They are effective for shear loads but have lower withdrawal resistance compared to screws.
- Screws: Threaded fasteners that provide higher withdrawal resistance and clamping force than nails. They are versatile for various applications.
- Bolts/Dowels: Cylindrical fasteners inserted through pre-drilled holes. Bolts typically have heads and are used with nuts and washers, while dowels are pin-like and rely on the snug fit or adhesive.
- Lag Screws: Heavy-duty screws with coarse threads, often used in structural applications where strong withdrawal resistance is needed without access for a nut.
- Timber Rivets: Steel fasteners driven into timber members to create strong connections, often used in conjunction with steel plates in heavy timber structures.
- Self-tapping Screws: Designed to tap their own threads into the material as they are installed, potentially eliminating the need for pre-drilling in certain wood types or applications.
Timber Connection Systems and Connectors
These systems often involve metal plates, hangers, or specialized components used in conjunction with fasteners to strengthen joints, transfer complex loads, or create specific types of connections.
- Joist Hangers: Prefabricated metal connectors shaped to hold floor joists or beams where they connect to supporting ledgers or beams. They provide strong support and simplify installation.
- Bolted Connection Types: Various joint configurations that primarily utilize bolts, often incorporating steel plates or washers to increase the bearing area, enhance strength, and transfer loads efficiently between members.
- Truss Plates: Metal plates with integral teeth or nails, pressed into timber members to join them together, most commonly used in the fabrication of lightweight roof and floor trusses.
- Split Rings: Metal rings installed in pre-cut circular grooves between two timber members. A bolt passes through the center, drawing the members together and transferring shear load through the ring bearing against the wood in the grooves.
- Shear Plates: Circular or square metal plates inserted into the surface of timber members in pre-cut daps. Used with a bolt, they provide a larger bearing area to transfer shear load and can allow for demountable connections.
- Glued-in Rods: Steel rods or bars bonded into pre-drilled holes in timber members using high-strength epoxy or polyester resins. This method creates very strong, rigid connections capable of transferring tension, compression, or bending loads, often used in engineered timber like Glulam or CLT.
These diverse methods allow engineers and builders to create robust and reliable timber structures for a wide range of purposes.
