Tie rod


Tie rod
Tie rods supporting the London Eye, England
Tie rods and anchor plates in the ruins of Coventry Cathedral

A tie rod is a slender structural unit used as a tie and (in most applications) capable of carrying tensile loads only.

Subtypes and examples of applications

  • In airplane structures, tie rods are sometimes used in the fuselage or wings.
  • Tie rods are often used in steel structures, such as bridges, industrial buildings, tanks, towers, and cranes.
  • Sometimes tie rods are retrofitted to bowing or subsiding masonry walls (brick, block, stone, etc.) to keep them from succumbing to lateral forces.
  • The rebar used in reinforced concrete is not referred to as a "tie rod", but it essentially performs some of the same tension-force-counteracting purposes that tie rods perform.
  • In automobiles, the tie rods are part of the steering mechanism. They differ from the archetypical tie rod by both pushing and pulling (operating in both tension and compression). In the UK, these items are generally referred to as track rods.
  • In steam locomotives, a tie rod is a rod that connects several driving wheels to transmit the power from the connecting rod.
  • Tie rods known as sag rods are sometimes used in connection with purlins to take the component of the loads which is parallel to the roof.
  • The spokes of bicycle wheels are tie rods.

Physics and engineering principles

In general, because the ratio of the typical tie rod's length to its cross section is usually very large, it would buckle under the action of compressive forces. The working strength of a tie rod is the product of the allowable working stress and the rod's minimum cross-sectional area. If threads are cut into a cylindrical rod, that minimum area occurs at the root of the thread. Often rods are upset (made thicker at the ends) so that the tie rod does not become weaker when threads are cut into it.

Tie rods may be connected at the ends in various ways, but it is desirable that the strength of the connection should be at least equal to the strength of the rod. The ends may be threaded and passed through drilled holes or shackles and retained by nuts screwed on the ends. If the ends are threaded right- and left-hand the length between points of loading may be altered. This furnishes a second method for pre-tensioning the rod at will by turning it in the nuts so that the length will be changed. A turnbuckle will accomplish the same purpose. The ends may also be swaged to receive a fitting which is connected to the supports. Another way of making end connections is to forge an eye or hook on the rod.

An infamous structural failure involving tie rods is the Hyatt Regency walkway collapse in Kansas City, Missouri, on July 17, 1981. The hotel had a large atrium with three walkways crossing it suspended from tie rods. Construction errors led to several of the walkways collapsing, killing 114 people and injuring over 200.

See also


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Look at other dictionaries:

  • Tie-rod — Tie rod, n. A rod used as a tie. See {Tie}. [1913 Webster] …   The Collaborative International Dictionary of English

  • tie rod — n. 1. a horizontal rod serving as a TIE (n. 5) 2. a rod that connects certain parts in the steering linkage of a motor vehicle …   English World dictionary

  • tie rod — tie′ rod n. bui an iron or steel rod serving as a structural tie …   From formal English to slang

  • tie rod — noun either of two rods that link the steering gear to the front wheels • Hypernyms: ↑rod • Part Holonyms: ↑steering linkage * * * noun 1. : a rod used as a connecting member or brace : tie bar see buckstay illustrat …   Useful english dictionary

  • tie rod — [1] Any connecting red or bar, usually under tension. [2] A rod, or rods, connecting the steering arms together. It links the pitman arm and the idler arm to the steering knuckle arms. When the tie rod is moved, the wheels pivot …   Dictionary of automotive terms

  • tie rod — 1. an iron or steel rod serving as a structural tie, esp. one keeping the lower ends of a roof truss, arch, etc., from spreading. 2. Auto. a rod that serves as part of the linkage in the steering system. [1830 40] * * * …   Universalium

  • tie rod — /ˈtaɪ rɒd/ (say tuy rod) noun a metal rod serving as a tie (def. 25) …   Australian English dictionary

  • tie-rod — noun Date: 1839 a rod (as of steel) used as a connecting member or brace …   New Collegiate Dictionary

  • tie rod — noun a) A slender metal rod used to support or reinforce part of a structure b) Either of a pair of rods that link the steering mechanism to the front wheel or axle of some vehicles …   Wiktionary

  • tie rod — devices, usually in the form of rods or bars, attached to the expansion joint assembly whose primary function is to continuously restrain the full pressure thrust during normal operation while permitting only lateral deflection. Angular rotation… …   Mechanics glossary