Abstract
This study is aimed at offering fundamental data needed for development of an ultimate earthquake-resistant design method for steel frame structures. For this purpose, the shear strength and ductility of unstiffened box section members are evaluated from the results of large-deformation elasto-plastic FEM analysis for web plates including the effect of flange plates. As a result, it is obtained that the strength calculated in this analytical model is almost the same as the results excluding flange plates, and the ductility is slightly larger than the previous results. Furthermore, the required flange thickness is discussed from the viewpoint of strength and ductility through parametric study on flange thickness to web thickness ratio. Finally, the formula estimating the ductility capacity of web plates is proposed.
