The effects of internal forces, such as creep and shrinkage, are calculated by considering each part in the cross section. For example, consider a cross section composed of a concrete beam with concrete slab, with mild steel, and PT steel. For creep effects, only the beam and slab are involved since the other parts cannot creep. The initial axial strain and curvature for the beam and the slab are computed first using equations (2) and (3). These initial deformations are converted to initial part stress resultants using the following equations.

These initial part-restraining forces are transformed to the centroid of the composite section to form the initial section restraining forces. Finally, the initial section retraining forces are converted to element FEF assuming a linear variation in restraining forces over the element.