Calculating Forces in Gate Frame Members: Am I on the Right Track?

[VooDoo]

Hi all,

Trying to design a simple gate for the side of our house and in order to select the size of the square tube for the frame, I need to calculate the forces in the members of the frame.

I have tried the method of sections and joints, however both do not seem to work.

My next approach is to draw a fbd for each member then work out what the maximum bending moment is and then select a sqaure tube size based on that. If any tubes are in compression I will calculate buckling.

Just want to know if I am going down the correct path?

 

[Danger]

I must say that I honestly wonder sometimes if people over-think things. Are you trying to bar access to your home from a Jehovah's Witness or a water buffalo? It makes a tad bit of difference as to what structural integrity is needed. (And the buffalo is easier to reason with.)
As a good compromise, I'd go with 1/2" square mild steel tubing welded together. If the buffalo is really angry, kick it up to 1" tubing.

 

[Robot B9]

Yes, a FBD would be the way to go. After that you should add any axial loads and combine the results from the bending & moment results with a Morh analysis.

I am curious where you got the downward force at point b on your diagram. And while you might think that the vertical loads at the hinges are shared it would be best to consider that the full load was only taken by a single hinge, probably the bottom one.