In structural engineering, a rigid frame is the load-resisting skeleton constructed with straight or curved members interconnected by predominantly rigid connections, which resist movements induced at the joints of members. Its members can resist bending moment, shear, and axial loads.
The two common assumptions as to the behavior of a building frame are (1) that its beams are free to rotate at their connections or (2) that its members are so connected that the angles they make with each other do not change under load. Frameworks with connections of intermediate stiffness will be intermediate between these two extremes. They are commonly called semirigid frames. The AISC specifications recognize three basic frame types: rigid frame, simple frame, and partially restrained frame.[1]