Rotation capacity of plastic hinges and allowable degree of moment redistribution

Abstract

According to experimental and analytical studies, the shape of the stress-strain curve in the inelastic range has a significant influence on the rotation capacity of plastic hinges. The ductility of modern cold-worked reinforcing steel may be rather small, resulting in low values for the plastic rotation capacity. Therefore it is proposed to classify reinforcing steel in two groups: Type 1: Steel with high ductility Type 2: Steel with reduced ductility In the region of splices by overlapping, mechanical devices or welding, the average steel strains are rather small (often below the yield strain). Therefore it is proposed that splicing of the reinforcement by any type of splice is not allowed in the region where the formation of plastic hinges is anticipated in the analysis. Because of its importance for the plastic rotation capacity and the possible degree of moment redistribution, it must be possible to distinguish the type of steel (type 1 or type 2) clearly and easily on site, e.g. by different rib patterns.