Experimental Study of Composite Beams Made of Steel Tubes Filled with Concrete under the Confinement Effect of U-Links and Stud-Plate

Concrete strength improved substantially when lateral confinement stresses are provided. This effect has been exploited in this study in composite beams at the concrete compression zone. New type of confinement is used in this research. The confinement of concrete in the compression zone is accomplished by providing U-links and stud-plate systems. The U-links are steel bars in the shape of the letter U welded internally in a steel tube at the compression concrete zone. These tubes provide confinement effect similar to the stirrups used in reinforced concrete beams. The stud-plate element used in this study is made of steel bar welded to a horizontal plate at one of its end, while the other end is welded to the top of the steel tube at the compression zone from the inside of the tube. The main function of these two elements is to provide the concrete in the compression zone with confinement stresses. The composite beam is tested in bending under single load at the mid-span. The effect of the new confinement system is studied and compared with concrete filled tube without any confinement element. The failure mechanism is also a focus of this research along with the deflection at the mid-span of the beam. The effect of the new confinement system on the structural behavior of the composite beam is presented.