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The iterative approach based on the work by Robert Mast is used to perform the cracked section analysis (this procedure is covered in detail in the PCI Design Handbook). This iterative procedure consists of assuming a depth to the neutral axis, computing the section properties of the net cracked section, checking stresses at the assumed neutral axis location, and then revising this location as necessary to make the concrete stress equal to zero at the assumed neutral axis location. The analysis runs with all loads at once and cracks the section to the given load level. It then computes the effective moment of inertia for use in the final analysis.