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An eyebar is a structural element used in construction. It is usually a straight bar with a hole or "eye" at either end, and is often made of metal. Other components can be secured to the eyebar at the holes on each end, and when the structure is designed, eyebars are positioned so they are tensioned rather than compressed. This means forces pull on the bar rather than push on it, as the structural integrity of this bar relies on pulling forces rather than pushing or squeezing forces.
Very often the eyebar is an I-beam, or a metal beam that has an I-shaped profile. The ends of the eyebar in this case may feature one opening at either end or several; if the piece features several openings, it is usually secured to another structural element using bolts or rivets for added strength. In other cases, the eyebar may have a rectangular profile rather than an I-shape for structural rigidity and ease of construction. A common place to see such a component is on certain types of bridges, especially truss bridges.
The bar itself is usually uniform in thickness, though the length of the component can vary significantly according to its purpose. It may be secured at both ends, and other components may end up being secured to the eyebar anywhere along its length, though the forces placed upon the bar will need to be analyzed carefully during construction to ensure excess force is not placed in such a way that the beam can fail. The bars are usually heat treated for added durability, and they are made from rugged metals, most commonly steel. Sometimes the holes at each end are manufactured slightly smaller than necessary and are reamed out on site for a tight fit.
Sometimes eyebars are connected to each other to help spread the load endured by the overall structure. This is sometimes known as a chain link structure, as the connection of eyebars together resembles the look of a chain, much like those found on bicycles or motorcycles. The end of each eyebar is often rounded, and the hole is open at the center of the rounded end. Other eyebars can be secured to the first using a pin, bolt, or rivet; the size of the connecting component will vary according to the size and function of the structure, as well as the size of the bar itself.