Editing Tie rod

{{Short description|Slender structural unit}}
A '''tie rod''' or '''tie bar''' (also known as a '''hanger rod''' if vertical) is a slender structural unit used as a tie and (in most applications) capable of carrying [[tension (physics)|tensile]] loads only.
It is any rod or bar-shaped structural member designed to prevent the separation of two parts, as in a vehicle.
[[File:Coventry Cathedral ruins tie rods.JPG|right|thumb|upright|Tie rods and anchor plates in the ruins of [[Coventry Cathedral]]]]

== 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 [[bridge]]s, industrial buildings, [[tank]]s,<ref>{{Cite book |last=Office |first=United States Patent |url=https://books.google.com/books?id=ltF8AAAAMAAJ&pg=PA2019 |title=Official Gazette of the United States Patent Office |date=1903 |publisher=U.S. Patent Office. |language=en}}</ref> [[tower]]s, and [[crane (machine)|crane]]s.
* Sometimes tie rods are retrofitted to bowing or subsiding masonry walls (brick, block, stone, etc.) to keep them from succumbing to lateral forces. The ends of the rods are secured by [[anchor plate]]s which may be visible from the outside.
* 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 [[automobile]]s, the ''tie rods'' are part of the [[steering]] mechanism. They differ from the archetypal 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 locomotive]]s, a ''tie rod'' is a rod that connects several [[driving wheel]]s to transmit the power from the [[connecting rod]].
* Tie rods known as ''sag rods'' are sometimes used in connection with [[purlin]]s to take the component of the loads which is parallel to the [[roof]].
* The [[spoke]]s of [[bicycle]] [[wheel]]s are tie rods.
*In ships, tie rods are bolts which keep the whole engine structure under compression. They provide for fatigue strength. They also provide for proper running gear alignment which prevents [[fretting]]. They help to reduce the bending stress being transmitted to the transverse girder.

== Physics and engineering principles ==
In general, because the ratio of the typical tie rod's length to its [[Cross section (geometry)|cross section]] is usually very large, it would buckle under the action of [[compression (physical)|compressive]] [[force (physics)|force]]s. The working strength of a tie rod is the product of the allowable working stress and the rod's minimum cross-sectional area.

If [[Screw thread|threads]] are cut into a [[cylinder (geometry)|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 [[shackle]]s and retained by [[Nut (hardware)|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 [[Tensile structure|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 [[swage]]d 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|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.

==Geometry==
Osgood and Graustein used the [[rectangular hyperbola]], its [[conjugate hyperbola]], and [[conjugate diameters]] to rationalize tie rods at 15 degree radial spacing, to a square of [[girder]]s, from its center. The tie-rods to the corners (45°) correspond to the asymptotes, while the pair at 15° and 75° are conjugate, as are the pair at 30° and 60°. According to this model in [[linear elasticity]], the application of a load compressing the square results in a [[deformation (mechanics)|deformation]] where the tie rods maintain their conjugate relations.<ref>[[William F. Osgood]] & William C. Graustein (1922) [http://quod.lib.umich.edu/u/umhistmath/abn6056.0001.001/324?rgn=full+text;view=pdf Plane and Solid Analytic Geometry], page 307, link from University of Michigan Historical Math Collection</ref>

==See also==
* [[Guy-wire]]
* [[Tie (engineering)]]

==References==
{{Reflist}}

{{DEFAULTSORT:Tie Rod}}
[[Category:Building materials]]