Eyebar

In structural engineering and construction, an eyebar is a straight bar, usually of metal, with a hole ("eye") at each end for fixing to other components. Eyebars are used in structures such as bridges, in settings in which only tension, and never compression, is applied. Also referred to as "pin- and eyebar construction" in instances where pins are being used. A closed eyebar will typically have a rectangular cross section of constant thickness throughout its length and a constant width for all but the ends. The ends will transition to a wider part that is terminated by a rounded end. In the center of this end will be a hole which will receive a cylindrical pin, which may have provision to accept one or more nuts or bolts. If of round cross section the bar will typically be end-forged to create a head, which is then flatted by additional forging. The head may then be machined to a precise thickness and flatness. An alternative method for using round bar is to form a loop and to forge-weld (hammer weld) or electrically weld the free end to the main bar. Open eyebars are not used in the cable anchorages of modern wire-cable suspension bridges. This does not allow the wires to be looped over the eye, rather than requiring threading through a closed eye. The bars may be fabricated with pin holes that are slightly undersized. If so, these are then reamed in the field. This field reaming ensures that stresses will be uniformly distributed among the several bars forming the truss element or the chain link. Corrosion resistant treatment in the form of grease, white or red lead oil paste, or other water-excluding material may be added at the time of the assembly. Eyebars are used in portions of pin-jointed trusses where it can be established by engineering procedures that the bar will not be imposed with any stress other than tension under all expected conditions. Eyebars are used to supplement roof truss framing supports made of wood or metal. They are placed as the struts for the truss, located next to the king joist.