Practical analysis for high-strength CFT columns under eccentric compression

An analytical study is carried out to investigate the elasto-plastic behavior of concrete filled, square steel tubular columns (square CFT columns) subjected to eccentric compression. A total of twenty-one specimens with high strength materials were tested in the fifth phase of U.S.-Japan Cooperative Earthquake Research Program on Composite and Hybrid Structures from 1993 to 1997. The experimental ultimate moments are compared with calculated moments by two design formulas. The flexural behaviors of the tests are also compared with the elasto-plastic analysis using the proposed stress-strain relationships for filled concrete and locally-buckling steel tube. The load-deformation curves obtained by the tests are fairly predicted by the practical analysis using the stress-strain models. However, flexural stiffness is overestimated by the analysis due to the effect of the residual stresses in steel tubes.