Twisting at shear center / centroid

[fonseh]

Homework Statement

In the notes , the author stated that when the force is applied through the centorid of cross section , the channel will bend and twist.
but , on the second page , the author stated that the shear center lies on an axis of symmetry of member's cross sectional area...
So, i am confused whether the member will twist or not when the force P is applied thru the centroid or shear center ...

Why the shear center is located at O , which is located outside of the C channel ?

Homework Equations

The Attempt at a Solution

Is there anything wrong with the notes ? [/B]

 

[fonseh]

In the notes , it's also stated that to prevent twisting , the P should be applied at O , does it mean we have to apply the force thru the centoid and also at the O at the same time to prevent twisting ? I'm confused

 

[fonseh]

Bump

 

[fonseh]

what is the meaning of the force is applied along the once vertical , unsymmetrical axis that passes thru centroid ? Since the applied force already passing thru centroid , it's already the symmertical axis , right ?