If the section area of wall is bxh=0.3mx9m,then 平面内Ib=bh3/12,平面外Ih=hb3/12 Ib/h=h2/b2=900/1 Therefore,Ih can be ignored.If the section area of wall is bxh=0.3mx9m, then 平面内Ib=bh³/12, 平面外Ih=hb³/12 Ib/Ih=h²/b²=900/1 Therefore, Ih can be ignored