Effect of relative stiffness on moment redistribution in reinforced high-strength concrete beams Available to Purchase

Moment redistribution in continuous concrete beams is primarily a structural aspect of behaviour, since it is a consequence of structural redundancy. However, the current design codes do not take this structural characteristic into consideration and therefore may not be reasonable when predicting the permissible moment redistribution. In this paper, moment redistribution in reinforced high-strength concrete (HSC) beams is analysed, focusing on the effect of relative stiffness represented by the structure-related parameter ρ_s2/ρ_s1 (where ρ_s1 and ρ_s2 are the tensile steel ratios over positive and negative moment regions, respectively). A numerical evaluation was conducted on two-span continuous beams made of HSC having a cylinder compressive strength of 90 MPa. A wide range of ρ_s2/ρ_s1 was produced by varying either ρ_s1 or ρ_s2 from 0·81% to 6·06%. The results show that the ρ_s2/ρ_s1 ratio is a critical parameter influencing the global moment redistribution behaviour. Modifications to the Canadian Standards Association and American Concrete Institute equations are proposed for calculating the moment redistribution at the ultimate state. By introducing the parameter ρ_s2/ρ_s1, the proposed modified equations are shown to have an excellent fit to the actual redistribution values.