Twelve frame specimens composed of wide flange beams and square steel tubular columns with or without filling concrete were tested in order to clarify the whole behavior of frames under constant vertical and varying horizontal loads. From the test results, it has become clear that frames with concrete filled tubular columns are very excellent as earthquake resistant structures when the beam-to-column connections are designed by the AIJ strength formula. The limiting value of width-thickness ratio of concrete filled square tubes and deformation performance are discussed.
