Bar Sysytem

in structural mechanics, a load-bearing structure composed of straight or curved bars interconnected by joints. The bar systems of engineering structures are usually geometrically fixed. Frames and trusses are typical examples of bar systems.

Bar systems can be classified according to their geometry as two-dimensional or three-dimensional. The system’s joints may be rigid or articulated, or they may be a combination of the two types. Rigid joints preclude rotation of the bars’ sections and are typically used in frames. Articulated joints permit such rotation and are typically used in trusses.

In calculating statically determinate bar systems, static equations suffice for determining reactions, internal stresses, and strains. A statically indeterminate system can be calculated either by precise methods of structural mechanics (work method, slope-deflection method, or a combination of more than one analysis method) or by approximation methods. The design of effective and economical bar systems depends on improved methods for calculating stability, particularly for systems composed of thin-walled bars, and also on methods for calculating the work done by the material beyond the limits of elasticity. The latter methods require a complex mathematical procedure and the use of computers.