The frames are generally supported on a roller support or on a hinged support. The reactions at the supports of a frame are determined by the conditions of equilibrium (i.e. sum of horizontal forces and vertical forces is zero). The external load on the frame and the reactions at the supports must form a system of equilibrium.
There are three conditions of equilibrium.
∑V = 0 (i.e. Algebraic sum of all the forces in a vertical direction must be equal to zero.)
∑H = 0 (i.e. Algebraic sum of all the forces in a horizontal direction must be equal to zero.)
∑M = 0 (i.e. Algebraic sum of moment of all the forces about a point must be equal to zero.)
