free body diagram

I think your free body diagrams are like this (you'll need to fill in the distances yourself):

Correction:  The top force for BE should say R_E not R_D

Another correction:  In the free body diagram of AC the force R_C is pointing up when it should be pointing down!

Alan, one of the moderators might be able to help you in this physics question, but is not online right now.

On rod AC , why we didn't consider the reaction at the top of rod BE ? 

Because a free body diagram only considers the forces acting directly on the (free) body in question.  The only force acting on AC from BE is R_B 

Very well, now for member BE what is Rd and Rb ? 

I think the following is probably what is needed (but you should check it carefully!).

Note:  The force on top of BE should be labelled R_E not R_D (which was a typo by me).  It will be the same in magnitude as R_B. 

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Yes Alan, you answer is correct. 

But I still have some problems with the free body diagram. 

1 - What is Rc ? is this the shear force ?? 

2- Is RE is the reaction of the support in beam BE ? 

3- What is RB in the beam BE ? 

those are my three questions and I will fully understand this problem.  

1 - What is Rc ? is this the shear force ?? 

In the free-body diagram for CD, R_C is the net force on CD due to AC (i.e. AC is helping to support CD and keep it from going down).

In the free-body diagram for AC, R_C is the reaction of CD on AC (Newton's 3rd law of motion).

2- Is RE is the reaction of the support in beam BE ? 

Yes, in free-body diagram BE, R_E is the force of the support at E on BE.  

3- What is RB in the beam BE ? 

In free-body diagram BE, R_B is the force of AC on BE (i.e. AC is trying to pull BE down).

In free-body diagram AC, R_B is the reaction force of BE on AC (i.e. BE is trying to keep AC up - Newton's 3rd law again).

Hope this helps.

Your answer is amazing. 

Thank you Alan.