ACI 318, How are Strength Evaluations Done on Existing
Strength considerations related to axial load, flexure, and combined axial load and flexure are well understood. There are reliable theories relating strength and short term displacement to load in terms of dimensional and material data for the structure.
To determine the strength of the structure by analysis, calculations should be based on data gathered on the actual dimensions of the structure, properties of the materials in place, and all pertinent details.
ACI Concrete Terminology:
Balanced Reinforcement – An amount and distribution of reinforcement in a flexural member such that in the working-stress design the allowable tensile stress in the steel and the allowable compressive stress in the concrete are attained simultaneously; or such that in strength design, the tensile reinforcement reaches its specified yield strength simultaneously with the concrete in compression reaching its assumed ultimate strain of 0.003.