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In this paper, the exact stiffness matrix of curved beams with non-uniform cross section is derived using direct method. The considered element has two nodes and twelve degrees of freedom with three forces and three moments applied on each node. The effect where the shear center -and center of area do not coincide is considered in this element. The cross
sections across the beam are deformed by bending, torsion, axial and shear loads. The curve representing center of area can have any curvature in the space and the cross section properties may change arbitrarily along it. The stiffness of three
kinds of beams have been determined by this method. In one type the results have
been compared with previous works and theoretical analyses. Finally it has been
- shown that the determined stiffness matrix is exact and all kinds of beams can be analyzed by this method.