2 方向水平力をうける H 形鋼柱の復元力特性モデルとその利用 : 2 方向水平地動をうける H 形鋼柱の弾塑性応答性状 (III) / A RESTORING FORCE CHARATERISTICS MODEL OF A H-SHAPED STEEL COLUMN DUE TO BI-DIRECTIONAL HORIZONTAL FORCES AND ITS APPLICATION TO EARTHQUAKE RESPONSE ANALYSIS : Inelastic Response of H-Shaped Columns to Bi-Directional Horizontal Earthquake Ground Motions (III)