Structural performance assessment of concrete filled steel strengthened beams with steel plates

Composite members consist of rectangular, circular and square steel tubes filled with concrete are extensively used in the construction of modern buildings, bridges, and particularly in zones of high earthquake risk. A very large number of structures have arrived the finale of their service life either caused by the change in the functional usage or degradation caused by environmental factors or due to a need of an increase in applied loads. Therefore, the strengthening techniques become essential to combat these problems. This study experimentally investigates the behavior of external strengthening of the square and rectangular Self-Compacted Concrete Filled Steel Tube (SCCFST) beams by attaching various steel plate thicknesses by bolts under flexural loading. A total of eighteen specimens which consist of 12 strengthened SCCFST beams, 3 control SCCFST beams, and 3 hollow steel tubes. The main parameters of this study are the width-to-depth ratio (B/H), rectangular and square sections and strengthening steel plates with two different thickness 3mm and 1.5mm fixed by bolts with four different arrangements. The flexural behavior of the strengthening SCCFST beams had been studied in terms of flexural strength, ductility and failure modes. Experimental results detected that the moment carrying capacity of the strengthened SCCFST beam is increased with the increasing thickness of steel plate and width to depth ratio. And also, ductility of strengthened SCCFST beams are decreased significantly with increase the width-to-depth ratio of the steel tube and the thickness of the steel plates. In addition, the B/H=1 is more ductile than the B/H=0.5 and 1.5.