The element stiffness in a particular iteration is adjusted based upon the influence of the cross sections (from either design sections or span segment strips) that have tributaries that intersect the element. In the instance where multiple cross sections cover an element at various angles, a weighted average and vector components squared of each cross section is used to determine the cross section’s influence on the element stiffness.

The axial and flexural element stiffness for each element in the model is adjusted based upon the ratio of the calculated gross curvature to the calculated mean curvature. For most normal situations, it will be possible to calculate equilibrium for the mean curvature and for cross section curvatures predominately caused by loading the gross and mean curvatures will have the same sign. Unusual cases are handled as follows:

• For the case where equilibrium cannot be achieved in a cross section calculation, a warning is logged in the calc log and the mean curvature is set to be 50 times the gross curvature. This is normally caused by inadequate reinforcement specified in the cross section without performing design, or an unexpected load combination is selected. This can sometimes occur as a normal part of the calculation process, where cracking in a highly stresses region shifts force to a less stressed region that does not have enough reinforcement to achieve equilibrium. In this case, this "softening" will effectively shift load back to the region that is designed to take it, and will predict both locations to be cracked.
• For the case where the mean curvature is opposite in sign from the gross curvature, the mean curvature is set to be 2 times the gross curvature. This will normally be caused by shrinkage strains larger in magnitude than the load induced strains, often times in regions of low bending. As a result, this modification will many times have little effect on the deflection calculations. No warning is issued for this situation.