Category Shear span/depth ratio Mode of failure Category I a,<1 Diagonal compression failure ho (斜压破坏) Shear-compression failure Category II ≤3 ho (剪压破坏) 2<6 Diagonal tension failure) Category III 3< ho (斜拉破坏) Category IV Flexural failure hoCategory Shear span/depth ratio Mode of failure Category I Category II Category III Category IV 1 0  h a v 1 3 0   h a v 3 6 0   h av 0 6 h a v  Diagonal compression failure Shear-compression failure (Diagonal tension failure) Flexural failure （斜压破坏） （剪压破坏） （斜拉破坏）