分布载荷q(x)的合力大小及作用线 (x R=[q(x)ax=图形面积 b x R b =图形形心 ldx f 12 23 R=gl R 2分布载荷q(x)的合力大小及作用线 q(x) x y O dx x a b =  =图形面积 b a R q(x)dx ( ) ( ) = =图形形心   b a b a R q x dx q x xdx x R xR O q l R l/2 q l 2l/3 R R = ql 2 ql R =