(1) 4 lastic hinge =0.65S =180S 777777 777777 =2.80S 7777 (a)Plastic-hinge mechanism Brittle failure 2) Disjoint 1=0.70S Plastic hinge 1.05S (2 【4) 3 乒120S 白180sS Disjoint Disjoint 1 (b)Brittle failure FIG.5.Formation of collapse mechanism:numbering denotes the sequence mixed hinges emerge 上海交通大学土木工程系 2008年上海交通大学土木工程系 2008年 (a) Plastic-hinge mechanism (3) (2) (4) Plastic hinge (1) (2) Plastic hinge Brittle failure (b) Brittle failure (1) t=0.65S t=1.80S (2) t=0.70S FIG.5. Formation of collapse mechanism: numbering denotes the sequence mixed hinges emerge (3) t=1.05S (4) Disjoint t=2.80S t=1.20S t=1.80S Disjoint Disjoint