ULTIMATE BENDING CAPACITY OF CIRCULAR TUBES.

A series of tests on 10-3/4 inch diameter tubes was conducted to determine the plastic rotation requirements of tubular beams. Three different D/t values (18, 35 and 102) were used in the tests. It was determined that tubes with D/t of at least 35 could develop the full plastic mechanism for a fixed ended beam with loading equivalent to a uniform load. Ovallization did not have a detrimental effect on the moment-curvature relation or on the plastic hinge formation. By testing beams with lengths of 20 and 50 feet, it was determined that shear was not a significant factor in the development of the mechanisms.