In this paper,a computer program for nonlinear analysis ofa special frame is developed.The frame has all columns fixed at the base and hinged at the top.By taking the frame as a whole,the behavior ofthe frame is studied from the test results of three specimens of the frame andlarge amount of results of computer program.The minimun value of total sumof vertical loads sustained by the frame is found and a new method of deter-mining the effective length of stepped columns is suggested.