Sectional Ductility of Wide Beams

Abstract

Wide beam structures are categorized as Limited Ductility Class in Turkey and elsewhere and considered not fit for construction in areas of high seismicity. One of the main reasons that wide beam structures are considered to possess limited ductility is the perceived low local ductility of the wide beams, due to the high reinforcement ratios. Wide beams have small depths, which indeed require higher reinforcement ratios to produce the necessary moment capacities, as compared to normal beams. However, the low local ductility of the wide beams can be contested. This paper presents a database of more than 150 beam sections, some of which are normal and some of which are wide beams. The moment-rotation relationships were computed for all the sections, and the sectional ductility was calculated from the yield and ultimate rotations. The relations between sectional ductility and other parameters such as section aspect ratio, longitudinal reinforcement ratio and transverse reinforcement ratio were investigated. An example of the relation between ductility and section properties, in this case section aspect ratio is shown. Both positive and negative ductility were calculated and plotted. It should be noted that beams with section ratio of 0.5 are conventional beams, while the rest are wide beams. The values of ductility vary for all beams, and conventional beams have a slightly wider spread. While these parameters vary within the section database, the sectional ductility oscillates around 30, and no clear correlations could be established for any of the above-mentioned parameters. There were no significant differences between the average sectional ductility of conventional and wide beams. For this dataset, the mean positive ductility was 29.66 and 29.33 for conventional and wide beams respectively, and the mean negative ductility was 28.96 and 31.50 for conventional and wide beams, respectively.