Abstract
Effect of yield ratio on Box Section Members' Ductility were investigated by numerical analysis. To consider the effect of local buckling and to get the accuracy of this simulation, stress-strain relations getting from stab-column tests were used, and also the conversion theory were made to get equivalent width-thickness ratio from real width-thickness ratio using bleich's local buckling theory. From this simulation, low yield ratio improve the members' ductility in case of small width-thickness ratio, but in case of large width-thickness ratio yield ratio is not effective on the members' ductility.