OS Zb Z bh3。b(h 式中Iz Z 12 2(4 62 h bh3(4 h maX 32 Q maX 2 bh 2 a式中 I b h Z = 3 12 , S b h Z y * = −       2 4 2 2  = −       6 4 3 2 Q 2 bh h y  max = = 3 2 3 2 Q bh Q A  max z b h