Experimental Study of Concrete Filled Built-Up Steel Tubular Beams

Using a new system of U-links and/or plated studs in CFT beams to join the steel tube with the concrete core in the compression side of the beam resulted in large confinement of the concrete core. Confinement is achieved by employing the separation expected between the two materials. A total of eight rectangular CFT beam specimens were tested under flexure with different ratios and different diameters for the U-links and/or plated studs were used to examine their effect on the flexural behavior of these beams. Ultimate flexural strength of the CFT beams with U-links and plated studs showed increase of strength about 45% of the specimens with ratio equals 37.5 above standard specimens with no links inside. State of the concrete inside the tubes has shown no crushing of the concrete when those beams were cut open at the location of plastic hinge. Strain measurements revealed that the compressive strain in concrete was 5-6 times the concrete crushing strain.