Tube reinforced concrete
Steel possesses high strength and ductility. Steel, as a structural member, especially as a compressive member such as columns, will have a limited stiffness. On the contrary, the concrete performs very well as a compression member. Concrete has excellent compressive strength and high stiffness. The combining of a steel tube and concrete to form a tube reinforced concrete will enhance the member strength, stiffness, ductility, and overall capacity. concrete-filled steel tube (CFST) is not just a steel tube with a concrete core. CFST will speed the construction process and enhance the load-carrying capacity and ductility of the structural members.
On the other hand, steel will reinforce the concrete and contribute to resisting the tensile stress, bending, shear, and providing sufficient ductility for the structure. The CFST is suitable for arch structures. The high compressive strength of CFST will be suitable for resisting the high compressive forces generated in arch structures such as bridges. THE CFST used to Wushan Bridge in china with a span length of 460 m.
Recently, Hollow CFST attracted significant attention in both research and application. Hollow CFST has many advantages over solid CFST. The using of hollow CFST will reduce the amount of materials used, which reduces the cost of the work. In addition to reducing the cost, the using of hollow CFST will increase the member capacity by the increase of moment of inertia. Also, it will provide a place for installing utilities such as cables or drainage pipes. The significant advantages of hollow CFST result in a rapid increase of using hollow CFST in the construction industry. Steel tubes with concrete forms a unique structure. Under normal conditions, concrete will develop a strong bond with the confining steel tubes. However, sometimes the concrete separate from the tube due to concrete shrinkage or bleeding. Therefore, expansive concrete is recommended to eliminate the separating of concrete from steel tubes.