in structural mechanics, a system or design in which the response to an external force perpendicular to a straight line passing through two hinges (or supports) is a reaction at an angle to the straight line. The two-hinged arch in Figure 1 is an example of a thrust system. In the presence of a vertical load, horizontal components of the reaction arise at the
hinges; these components are called thrust. Other examples of thrust systems are two-dimensional suspension systems and many three-dimensional systems, such as suspended shells, membranes, cupolas, and vaults.