Editing Tie rod (section)

== 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.