Two-Dimensional System

in structural mechanics, a system of construction in which the axes of symmetry of all elements and the lines of action of the external forces are located in one plane. In construction practice, two-dimensional systems are not used alone but are usually combined with one another in three dimensions. However, in order to simplify engineering calculations, many structures are treated as a combination of two-dimensional systems in computing procedures. For example, the skeleton of an industrial or public building, which constitutes a three-dimensional system, is replaced by a system of flat frames for analysis. A similar dissection into two-dimensional systems is performed when analyzing the trusses of bridge spans, hoisting cranes, and other structures.