Approximate calculation of internal force and sway of the semi-rigid jointed steel frame

The secondary-moment distribution method and Dvalue method of structural mechanics were modified by considering semi-rigid connection of the beam-column node and P-Δeffect.The calculation formulas of the end moments,the rotation rigidity and the transmission coefficient were derived by using three parameters mechanical model to simulate the moment rotation of beam-column connections of semi-rigid steel frame and helical spring to simulate semi-rigid connections of the nodes.An approximate calculation method for the internal forces and sway of the semi-rigid jointed steel frame were given by amending the Stiffness of beam and column.The results show that internal forces in the structure is redistributed as a result of connections of semi-rigid steel frame and the story deflections increases as a result of P-Δ effect,so the effect of the semi-rigid connection and P-Δ effect must be considered in design.The method of this paper is simple and clear,meets the desire of precision and is easy to use for engineering design.