Bending moment on top of the tower (tubular shell structure)

[beg1ner]

Hi, i have 50m height tubular structures which is made from shell elements. I need to put bending moment on top of this tower. How can i do this, to get same results as if tower would be simple beam? I'm using Robot Pro. Sorry for bad english.

 

[ash060]

If it is a bending moment around the whole tube and not about the individual elements, I would just apply a line load along the perimeter of the tube.

If you have the properties of the tube, just calculate the bending stress in the tube and you can use that number to define the line load. You will have a tension load on one face and a compression load on the opposite face. And if the program allows a linear varying load along the two other sides.

 

[BAretired]

I do not understand the question. Please provide a sketch.

BA

 

[beg1ner]

Thanks for post, I'm using Robot Pro. I already did that what you said, but i have problem. I only can put linear load(kN/m) on the edge of tubular structure, so how i can transfer bending stress(MPa) to linear load(kN/m) on the edge? I'll hope you understand.

 

[beg1ner]

Sorry for double post. In sketch you see tower's top. I need to put on this top of tower Mx=1.6e+6 bending moment. Radius=5.5m, wall thickness=0.05m. Maybe now it will be understandable.

 

[BAretired]

You show 16 segments.
1. Calculate segment width.
2. Calculate y_n to center of each segment.
3. Apply vertical point load P_n at center of each segment which is proportional to y_n.
4. Calculate Mx = sum of P_n*y_n.
5. Calculate k = 1.6e6/Mx
6. Apply k*P_n to each segment.

Done.

BA

 

[ToadJones]

What a lot of guys will do in a situation like this is add "dummy" members to the model that have zero weight and infinite stiffness. Yours could emanate from a point in the dead center of the tower in the place at the top of the tow and go radially out to the points on the outside of the shell. Then you can apply a moment to the node in the center of the tower and it should pretty accurately distribute forces to the shell.

 

[beg1ner]

Thanks everyone for answers.