Solving for forces/reactions and moments in a complicated frame

[salman213]

1.

http://img337.imageshack.us/img337/520/fic06p090bk7.png

http://img337.imageshack.us/img337/2763/vqc06p090je0.png​

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2. $$\sum$$Maboutapoint
$$\sum$$Fy
$$\sum$$Fx



3. Well firstly i just looked at it as a whole to see if i can figure out any of the reactions at F or B. I am confused about where to and where not to apply that moment of 48 Nm which is replacing the force at A.

For example when I am taking the moment about point F when looking at the system as A WHOLE, should i take into consideration that 48 Nm in the moment equation?

When I am taking it about point E of the WHOLE SYSTEM i do not? or no matter what, I have to add 48 Nm in all moment equations that i make?

And then please telll me when I DISMEMBER the frame when I am looking at the member FCA, is that the only time i take that moment into consideration, or no matter which dismembered part I am looking at, I have to take that moment of 48 Nm at point A into consideration in the MOMENT equation I make?
pleasezzzzzz help

 

[Pyrrhus]

In order to solve this problem, simply find the vertical (y-components) of the reactions F and B, by using the whole body, dismember for finding the horizontal (x-components).

Remember: Moments are Free vectors unlike forces which are sliding vectors.

 

[piercas]

I would first like to commend you for taking the time to analyze and understand this complicated frame. It is important to carefully consider all forces and moments in order to accurately solve for the reactions and moments in a frame.

To answer your first question, when taking the moment about point F, you do not need to consider the moment of 48 Nm at A. This is because the moment at A is already accounted for in the moment equation at F. Similarly, when taking the moment about point E, you do not need to consider the moment at A. This is because the forces and moments at A are already accounted for in the overall moment equation at E.

When dismembering the frame and looking at individual members, the moment of 48 Nm at A should only be considered for the specific member that it is acting on. For example, when looking at member FCA, you would include the moment of 48 Nm at A in the moment equation for that member. However, when looking at member FBE, the moment at A would not be included in the moment equation for that member.

It is important to always consider the specific forces and moments acting on each individual member when solving for reactions and moments in a complicated frame. This may require dismembering the frame and analyzing each member separately. I hope this helps clarify any confusion you may have had.