The behavior of concrete filled tube columns under seismic loads was studied through testing six columns which were subjected to a constant axial load in addition to a cyclic lateral load. The test parameters included the level of axial load, the diameter-to-thickness ratio of the steel tube, and the concrete strength. The test columns showed high ductility and maintained their strength up to the end of the test. The test results also indicate that the column capacity was significantly improvement due to the enhancement in the concrete strength due to the confinement provided by the steel tube.
