Upper Limit to Compression Reinforcement Ratio in Flexural Elements

The upper limit to the tension reinforcement ratio in flexural RC members is based on the requirement that tension failure as well as sufficient rotation capacity are ensured at ultimate limit state. However, the provisions for the total amount of longitudinal reinforcement ratio are not associated with any rational derivation. A quantitative measure to evaluate an upper limit to the compression reinforcement ratio $\rho {\prime }_{\mathit{max}}$ of flexural RC members is proposed. It is shown that a quantitative criterion to $\rho {\prime }_{\mathit{max}}$ can be derived from steel congestion and proficient-design considerations and from considerations that are related to the diagonal compression bearing capacity. Parameters that affect this limit include the concrete and steel strengths, the beam's geometry (L/d ratio, cross section's dimensions, and concrete cover), the steel bars' diameter, and the moment-to-shear loading ratio (or the loading type). When shear loading is dominant, the limit to ρ′ is set by the diagonal compression criterion, while in cases of dominant flexural loading (relative to the shear loading) $\rho {\prime }_{\mathit{max}}$ is determined by the congestion criterion.