FLEXURAL STRENGTH OF CONCRETE-FILLED STEEL TUBULAR BEAM WITH PARTIAL REPLACEMENT OF COARSE AGGREGATE BY GRANITE

Composite members consists of steel and concrete have the advantages of both materials, steel has high tensile strength and ductility, while concrete has the advantages of high compressive strength and stiffness . The main objective this research is to determine the load carrying capacity of steel tubular beams filled with different types of concrete (normal and partial replacement of coarse aggregate by granite) under bending action in construction works. The benefits of using partial replacement of coarse aggregate by granite is not only to enhance strength but also to preserve the natural resources of sand and also keeps these powder particles from being airborne into the atmosphere causing health hazard to humans, in particular children . It is widely recognized that the innovative use of two or more material in structures generally leads to more efficient economical systems for resisting forces. In this area utilizing of concrete filled steel tubes are new idea which increasingly finding application in design practice. Current design codes and standards provide little information on the flexural behaviour of Concrete Filled Steel Tubes (CFST). There are significant differences in d/t limits recommended in various codes for CFST under bending. This paper presents an experimental investigation of the flexural behaviour of square concrete filled steel tubes (SCFST) subjected to pure bending, where the depth to thickness ratio (d/t) is 23.8 & 27.8. The paper compares the behaviour of empty and concrete-filled, hot rolled rectangle hollow sections under pure bending. The behaviour of such concrete filled steel tubular beams with partial replacement of coarse aggregate by granite under flexural loading is presented. The effects of steel tubes, compressive strength of concrete and the confinement of concrete are examined. Six specimens were tested with strength of concrete as 20 MPa. The beams were 88.9X88.9 and 114.3X114.3 mm in size and 1200 mm in length. From the test results it was observed that the ultimate load carrying capacity of steel tubular beams filled with partial replacement of coarse aggregate by granite is almost the same as that of conventional concrete. In general, filled steel tube enhances strength, ductility and energy absorption especially for thinner sections. The steel shell provides confinement for concrete core thus increases the ductility and strength of core. The use of concrete filled steel tubular sections in structural frames has increased in different countries such as United States, and Australia during the past ten years.