The previous sections describe the procedures used to compute incremental nodal displacements and rotations for an interval. When forces are needed on the box girder, PT, or reinforcing, i.e., cross section part forces are needed, the following procedure is used:

• Element end forces are calculated using standard matrix structural analysis procedures in which the incremental displacement and rotations are multiplied by the element stiffness matrix applicable for the interval (since the modulus can vary with time, and in the presence of creep, the element stiffness matrix is different for each interval), and the element fixed end forces are added.
• The axial strain and curvature for the section are calculated using the forces on the composite section (the element forces) and the transformed section properties.
• The axial strain at the level of the part is computed and subsequently the force and moment on the part is calculated.
• The axial strain and curvature for the section are calculated using the initial section restraining forces and the transformed section properties.
• The axial strain at the level of the part is computed and subsequently the force and moment on the part is calculated.
• The initial part restraining forces are added in.