列出用力法求解的基本方程
?11X1??1P?0
(2) 求?1P
由上图知
A 2 C 1 3 B A 2 1 C 1 3 B ? ? D ? ? P N1?0 N1?1
D 分别对D点受力分析
2sin?由莫尔定理
3N2 D N1 α α N3 P P2sin?N2 N1 α α D N3
N2?P N3?? N2??12cos? N3??12cos?
?1P???i?1NiNiliEA[0?1lP1l???????????????]?0?????2sin??2cos??cos??2sin???2cos??cos?P1EA
(3) 求?δ11
3?11???i?1NiNiliEA?l????[l???????]???EA?2cos??cos??2cos??cos?112l12
l?1?1???3EA?4cos??(4) 求出X1
X1?0
(5) 求杆的内力
N1?N1?N1?X1?N1?0N2?N2?N2?X1?N2?PPPP2sin?P2sin?
N3?N3?N3?X1?N3??