ELASTIC-PLASTIC BEHAVIOR OF CIRCULAR HOLLOW STEEL TUBE SECTIONS SUBJECTED TO BENDING

Abstract

ABSTRACT The current study aims to investigate the elastic-plastic behavior of steel circular hollow sections under bending loading. The experimental work of this study included a series of bending tests in order to examine and determine the effect of the section thickness, diameter and beam span on the structural behavior of steel tubes. In addition, the effect of the presence and number of square openings on the behavior of these sections was studied. The loading type used to study the bending behavior of steel tubes was simply supported beam test by two points load. Ten circular hollow beam specimens were performed and tested up and post to failure stage with thickness (2, 3 and 6 mm), diameter (76.2, 101.6 and 219 mm) and span (1000, 1500 and 2000 mm). From these specimens, one was chosen as a reference specimen and used with thickness, diameter and span equal to (3, 101.6 and 1500 mm) respectively. The experimental results showed that increasing the section thickness to (6 mm) improved the structural strength capacity by (81.75%) compared with the reference specimen, at the same time led to increase the specimen ductility significantly by (58.04%) which led to the gradual drop in the loads carrying capacity for this specimen. While decreasing the section thickness to (2 mm) reduced the structural strength capacity and ductility by 38.87%, and 64.86% respectively compared with the reference specimen. II Increasing the specimen diameter to (219 mm) led to a very high increase in the structural strength capacity by (237.59%) compared with the reference specimen, but it led to reduce the ductility significantly by (76.67%) which caused the sudden drop of the specimen loads when it reached to the ultimate load. While decreasing the specimen diameter to (76.2 mm) reduced the structural strength capacity by (56.75%). Increasing the specimen span to (2000 mm) reduced the structural strength capacity and ductility by 3.28% and 37.13% respectively compared with the reference specimen. While it was found that the decrease in the specimen span to (1000 mm) improved the strength capacity by (89.78%) compared with the reference specimen, but at the same time reduced the specimen ductility. The presence of one, two or three square openings in the specimens reduced their ultimate strength by (17.88%, 19.71% and 14.23%) respectively, and also reduced their ductility significantly by (72.40%, 67.71% and 60.88%) respectively and caused the sudden failure for these specimens. In addition to the experimental work, a theoretical analysis has been conducted for these ten specimens by using the ANSYS program (version 13), the load-deflection results of this analysis showed a good agreement with the experimental results. It also has been performed a parametric study that included two variables which were the effect of the presence of circular rings and the change of opening location in the length direction on the specimens behavior. The results of this study showed that the presence of the circular rings in the specimen led to increase its ultimate strength by (53.24%) compared with the non-presence of these rings. While the presence of opening at (30%, 40% and 50%) from the specimen length reduced the strength capacity by (8.76%, 14.23% and 17.88%) respectively.