STRENGTH PREDICTION OF STEEL TUBULAR SQUARE COLUMNS IN-FILLED WITH CONCRETE

The behaviour of concrete filled steel tubular (CFST) square column sections with various concrete (partial replacement of fine aggregate by fly-ash and quarry dust and coarse aggregate by granite and construction & demolition debris) strength under axial load is presented. The effects of steel tube size, length and the confinement of concrete are examined. Measured column strengths are compared with the values predicted by Eurocode 4, Australian Standards and American Codes. 18 specimens were tested with strength of concrete as 20 MPa, L/D ratio varies from 4.16 to 12.5 and a D/t ratio of 22.5. The columns were 72.0 mm in side, 3.2 mm in thick and are 300, 600 & 900 mm in length. All the three codes and modified ACI/AS predicted lower values when compare to experimental results. Hence ACl/AS equation is proposed by multi plying factor ‘k’ to predict good results for columns of L/D < 12 In this study k factor for varies L/D ratio from 4 to 12 are suggested. Modified ACI/AS gives the best estimation for CFST sections with 900 mm column length.