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In this paper, a series of formulas corresponding to the so-called Unified Design Method (UDM) characterizations
of tension-controlled, compression-controlled, and, transition-zone beam sections are presented. The formulas are
in terms of reinforcement ratios and completely avoid the use of strain limits and/or c/d ratios. Many of the
formulas presented here are well known and established, but a few are new. In particular, a formula for the
compression-controlled reinforcement ratio limit is introduced and a direct design procedure for transition-zone
sections is developed and described. It is hoped that the formulas and ideas presented in this paper will prove
useful both for the instructor in the classroom, and for the practicing structural engineer. Somewhat detailed
derivations of most of the formulas in the paper are presented and several numerical examples to illustrate their
use are provided at the end of the paper.
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