This document discusses stress diagrams and design considerations for singly reinforced concrete beams. It covers notation, stress conditions, types of failure, and formulas for moment of resistance. The key points are: 1) A stress diagram shows the compression and tension zones of a beam based on the depth of the neutral axis. The moment of resistance depends on the neutral axis location. 2) Beam sections can be balanced, under-reinforced, or over-reinforced depending on when concrete or steel yields. Under-reinforced sections are preferred. 3) Formulas are provided to calculate the moment of resistance based on the steel or concrete stresses for different section types. Reinforcement criteria specify minimum and maximum steel ratios.