Upper Limit to Compression Reinforcement Ratio in Flexural HSRC Members

limit to the tension reinforcement ratio in flexural high strength reinforced concrete (HSRC) members is based on the requirement that tension failure as sufficient rotation capacity are ensured at ultimate limit state. However, the provisions for the maximum amount of compression reinforcement ratio (ρ'max) in a doubly reinforced section are not associated with any rational derivation. A quantitative measure to evaluate an upper limit to the compression reinforcement ratio (ρ'max) of such flexural HSRC members is proposed. The quantitative criterion to ρ'max can be derived from i) steel congestion and ii) considerations that are related to the diagonal compression bearing capacity of the members. In this paper it is shown that, when flexural loading is dominant the shear loading, the limit to ρ' is set by the steel congestion criterion. Parameters that affect this limit such as, f 'c, beams geometry (cross sectional dimension and concrete cover), and bars diameter are deeply investigated and the expressions were derived to provide an additional tool for a better design and assessment of the flexural capacity of HSRC members considering different end conditions and loading arrangement. Keyword: Steel Congestion Criterion, End Conditions and Loading, HSRC and Upper Limit to ρ'.