The investigation presents a method of analysis of a rigid frame built of mild steel, when the horizontal beam member is stressed beyond the yield point of the material. The frame is a 'U' type made up of rectangular members with welded joints. Prediction equations have been developed for deflections, frame spread, angle changes of the joints, moments, and sheers. Deflections, frame spread, angle changes, and moments have been measured and compared with predicted values;A restrained beam of mild steel, rectangular in cross section, was tested with a concentrated load at the center and equal moments on the ends, and the deflections measured. Prediction equations of deflection have been developed and compared with measured values of deflection;Testing method and procedure have been developed for a rigid frame and a restrained beam, involving ductile behavior, for use in the laboratory.