Forces not in equilibrium at joints in hydrostatic problem

[AngelofMusic]

Hello,

I'm currently trying to solve a problem involving hydrostatics, but I'm getting stuck when it comes to drawing the forces in the FBD.

The original problem is here:

http://img.villagephotos.com/p/2003-11/466966/hydrostatics.jpg

This is my attempt at drawing the FBD:

http://img.villagephotos.com/p/2003-11/466966/fbd.jpg

My calculations:

R(water) = 187.3 kN
R(mud) = 644.7 kN

I think that should be correct.

However, once I isolated the joint at the intersection of A,B, and C, there is no way I can get the joint to be in equilibrium. (See the bottom right corner of my FBD).

The same problem occurs at D, where the compression force in member D only goes up vertically, but I also have a horizontal component to the reaction force at D.

What am I doing wrong? Does anyone have any hints/suggestions on how to solve this?

Thanks a lot!

 

[HallsofIvy]

However, once I isolated the joint at the intersection of A,B, and C, there is no way I can get the joint to be in equilibrium. (See the bottom right corner of my FBD).

You will need to assume that A and D are set in at their base (not hinged) so that they can support sideways forces.

 

[AngelofMusic]

Okay, so would the FBDs look something like this, then?

http://img.villagephotos.com/p/2003-11/466966/fbd2.jpg