Empirical Investigation of Flexural Reinforced Concrete Elements with High Compression Reinforcement Ratios

The moment capacity and failure modes of four types of beams with high reinforcement ratios are reported. The tests were planned and conducted in order to examine a quantitative measure that had been proposed to evaluate an upper limit to the compression reinforcement ratio ${\rho }_{\max }^{\prime }\text{,}$ for flexural reinforced concrete members. The concept that was examined was the derivation of a quantitative criteria for ${\rho }_{\max }^{\prime }$ from steel congestion and proficient design considerations (i.e., tension failure and sufficient rotation capacity at the ultimate limit state) and from considerations related to diagonal compression capacity. The tests were designed with relatively high compression reinforcement ratios of up to 4.8%, in order to show the influence of parameters that affect this limit, i.e., the beam geometry $(L/d$ ratio, cross-section dimensions, and concrete cover), and the moment-to-shear loading ratio. The results of the tests reported here agreed with the trends as well as the quantitative predictions of the theoretical moment capacities. Thus, they strengthen the proposed approach for setting an upper limit to the longitudinal compression reinforcement ρ^′ in flexural reinforced concrete members.