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Experimental and Analytical Investigations of Composite Stub Columns

Hasan Abdulhadi Ajel , Abdulnasser M. Abbas

The structural behaviour of concrete - filled steel tube (CFST) columns has been investigated using experimental and analytical studies. The effect of concrete compressive strength, thickness of steel tube, stiffeners and longitudinal reinforcement were considered. Specimens that have been studied consist of sixteen square samples with dimensions of 150 mm ×150 mm × 300 mm height, and fifteen circular samples of 150 mm diameter and height of 300 mm. The tested samples were studied analytically using three dimensional finite element representation by ANSYS (ver. 12.1) computer program. Eight nodes brick elements SOLID 65 and SOLID 45 were used to simulate concrete and steel tube respectively. While two nodes element LINK 8 are used for steel rebar. The results obtained from finite element solution shows that, the convergence between analytical and experimental failure load varied from 2 to 15 %. While the effect of compressive strength of concrete on columns having width/thickness (b/t) or diameter/thickness (d/t) 37.5 is greater than columns which have (b/t) or (d/t) 50. Deformations of columns filled with normal concrete (25 MPa) are larger than those of columns filled with high strength concrete (60MPa). The effect of width-thickness (b/t) and diameter/thickness (d/t) ratio on the ultimate strength of (CFST) columns will have a reverse action, when of (b/t) or (d/t) decreases the caused increasing in ultimate load capacity of columns which is varied from 4.47 to13.37 % for square samples varied from 8.00 to 12.14% for circular samples depending on the type of stiffened, compressive strength of concrete and ratio of (b/t) and (d/t).