Evaluation of Moment Redistribution in Normal-Strength and High-Strength Reinforced Concrete Beams

This article presents an investigation of redistribution of moments in normal-strength concrete (NSC) and high-strength concrete (HSC) continuous beams. A nonlinear computer model is introduced and validated by experimental results of HSC continuous specimens. A numerical test is performed on two-span continuous beams where the concrete strength varies between 30 and 90 MPa so as to cover both NSC and HSC beams. Various tensile steel ratios over the center support ρs2 and midspan ρs1 are used. Some rules related to moment redistribution are examined. The study confirms that the moment redistribution is dependent on the stiffness of the critical sections. The analysis also indicates that full redistribution of moments is more likely to be developed in HSC beams than in NSC beams. The results of a parametric study, where the ratio ρs2/ρs1 is fixed at 0.8, show that at a given steel ratio, a higher concrete strength registers higher redistribution of moments except when ρs2<1.55 precent. The effect of concrete strength on the moment redistribution is generally reflected in various codes.