ABSTRACT
By using basic formulas, one establishes internal forces in a beam-column in its standard unit states, and obtained internal force distributions are employed in the displacement method. The first stage of calculation by the displacement method is to determine the degree of kinematic indeterminacy and to construct a primary system. The transition to a conjugate truss with a view of seeking axial forces is a calculating trick which is not compulsory in the displacement method. According to the theorems proved, shear forces and bending moments at the sections of a primary system are calculated under assumption of axial forces corresponding to the frame pure compression. Bending moments and shear forces wanted for calculation of reactions are determined as the differentials with respect to the vector of support displacements under axial forces of the frame’s pure compression. On zero degree of freedoms, a given frame is in the state of pure compression and fictitious loads are equal to zero.
