Tie (engineering)

A tie, strap, tie rod, eyebar, guy-wire, suspension cables, or wire ropes, are examples of linear structural components designed to resist tension.[1] It is the opposite of a strut or column, which is designed to resist compression. Ties may be made of any tension resisting material.

A hurricane tie used to fasten a rafter to a stud

Application in wood construction

In wood frame construction they are generally made of galvanized steel.[2] Wood framing ties generally have holes allowing them to be fastened to the wood structure by nails or screws. The number and type of nails are specific to the tie and its use. The manufacturer generally specifies information as to the connection method for each of their products. Among the most common wood framing ties used is the hurricane tie or seismic tie used in the framing of wooden structures where wind uplift or seismic overturning is a concern.

Hurricane tie
Hurricane ties are in place at the top of the wall as the roof trusses are being placed.

A hurricane tie is used to help make a structure (specifically wooden structures) more resistant to high winds (such as in hurricanes), resisting uplift, racking, overturning, and sliding.[3] Each of the crucial connections in a structure, that would otherwise fail under the pressures of high winds, have a corresponding type of tie, generally made of galvanized or stainless steel, and intended to resist hurricane-force and other strong winds.[4]

A connecting tie that provides a continuous structural load transfer path from the top of a building to its foundation, helping to protect buildings from damage resulting from high wind. These devices are primarily used in areas affected by high winds including hurricanes and are generally suitable for any area that may be impacted by windstorm damage. They are also known as hurricane clip or strips. Among the most common style used along the gulf coast area are plywood fasteners or oriented strand boards over the windows and openings of brick homes. Hurricane clips meet the minimum requirements for code approval and are only as strong as their weakest install point; which is generally half the strength of the wood.

A hurricane clip has two meanings in building construction:

  • A connecting tie that provides a continuous structural load transfer path from the top of a building to its foundation, helping to protect buildings from damage resulting from high wind. These devices are primarily used in areas affected by high winds including hurricanes and are generally suitable for any area that may be impacted by windstorm damage. They are also known as hurricane ties[4] or strips;
  • A tie which is attached to roof tiles to keep them from blowing off a roof. These devices are also known as wind clips and hurricane side clips[5]

Seismic tie

Seismic tie provides facility to securely fix cabinets, bookcases, desks, appliances, machinery & equipment to walls and/or floors to constrain their movement during earthquakes. [6]

Girder tiedown

Top mount, face mount, sloped/skewed, and variable pitch hangers for dimensional lumber, engineered wood I-joists, structural composite lumber and masonry wall. To give added strength in increase various load requirements over wood only.

Strap tie

When building subfloor the joists must always bear on the ledge for all it support. The use of steel stap tie to connect opposite joist when the top of the joists and beam are flush.[7]

Twist strap

Twist straps provide a tension connection between two wood members. They resist uplift at the heel of a truss economically. When the strengthening is being done from the inside, the ideal connector to use is one that connects rafters or trusses directly to wall studs. This can only be done where the rafter or trusses are immediately above or immediately to the side of studs below. In that case a twist strap connector can be used.[8]

Floor span connector

A connector for connecting wall studs of two adjacent floors in a light frame building structure, the connector having a first attachment tab, a seat member, a diagonally slanted support leg, and a second attachment tab, all substantially planar. The connector is intended to be paired and the paired connectors joined by an elongated tie member that pierces the sill plates of the intervening floor structure.

Angle tie

Sometimes referred to as an angle brace. The Angle tie is used to prevent displacement of building elements due to thrust. A brace/tie across an interior angle of a wooden frame, forming the hypotenuse and securing the two side pieces together.[9]

Z-clip

Similar to a French cleat, a Z-Clip allows for the installation of wall panels without screwing into the front of the panels. The clips provide a secure mount for wall panels, partitions, frames, cabinets, and more. Once installed, clips wedge together to lock panels in place. To disengage panels, simply lift and remove.

Plate
Metal connector plates.

See

Main article: truss connector plate

Rafter tie (and Tie-beams)

Rafter ties are designed to tie together the bottoms of opposing rafters on a roof, to resist the outward thrust where the roof meets the house ceiling and walls. This helps keep walls from spreading due to the weight of the roof and anything on it, notably wet snow. In many or most homes, the ceiling joists also serve as the rafter ties. When the walls spread, the roof ridge will sag. A sagging ridge is one clue that the home may lack adequate rafter ties. Rafter ties form the bottom chord of a simple triangular roof truss. They resist the out-thrust of a triangle that's trying to flatten under the roof's own weight or snow load. They are placed in the bottom one-third of the roof height. Rafter ties are always required unless the roof has a structural (self-supporting) ridge, or is built using engineered trusses. A lack of rafter ties is a serious structural issue in a conventionally framed roof.

The 15th-century tie-beam roof at St Marys Church, Radnage, Buckinghamshire in England

A wooden beam serving this purpose is known as a tie-beam and a roof incorporating tie-beams is known as a tie-beam roof.[10]

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See also

References
  1. Trautwine, John Cresson (1919) [1871]. The Civil Engineer's Pocket-Book (20th ed.). Wallingford, Pennsylvania: Trautwine Company. p. 359. Retrieved February 12, 2010 – via Internet Archive. A long slender piece sustaining tension is called a tie. One sustaining compression is called a strut or post.
  2. "Different coatings available". strong-tie.com.
  3. "How wind affects your home". safestronghome.com. (A Simpson Strong-Tie website)
  4. Rumbarger, Janet, Richard Vitullo, and Charles George Ramsey. Architectural graphic standards for residential construction. New York: John Wiley & Sons, 2003. 238. Print.
  5. Document from a commercial website
  6. "Seismic Technical Guide" (PDF). USGUSG Seismic Ceiling Resource Center. usg.com. Retrieved 23 May 2015.
  7. Anderson, LeRoy Oscar (28 Nov 1992). Wood-frame House Construction. USA: Craftsman Book Company. p. 35. ISBN 9780934041744.
  8. Douglas, Howard. "Wood Frame Roof-to-Wall Connections". Florida Hurricane Retrofit Guide. Division of Emergency Management. Retrieved 23 May 2015.
  9. "Right-angle brace gives you a corner on clamping tasks". Wood Magazine. Wood Magazine. Retrieved 24 May 2015.
  10. "2308.10.4.1 Ceiling joist and rafter connections". International Code Council. Retrieved 24 May 2015.
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