ABSTRACT
Results are presented of tests on rectangular hollow sections filled with high strength concrete when used as beams. Steel fibres of 18 mm length with enlarged ends are added to the concrete mix in some of the beams. Study found that once filled with high strength concrete, both strength and ductility increase significantly. The buckling mode of the steel section is changed from the usually approximate sine wave to the approximate cosine wave, indicating high buckling strength. The brittle characteristics related to the high strength concrete is totally eliminated due to the confinement of the steel section and due to the fibre steels to some extent at the post-failure range. A simple flexural strength theory is derived for design application. Comparisons are made between the test and the predicted results.
