How to model compression only member in SAP2000 for oil tank scaffolding design

[JoeH78]

Dear Community Members,

I need to design a scaffolding which will be assembled around an oil tank, scafollding is steel inter-locking "H" type system. The oil tank is 13.5mt in diameter (cylinder shaped) and 18mt tall steel structure, I can not tie the scaffolding laterally to the oil tank via welding or screwing since this can be dangerous and may pose serious safety issues. Due to that, As design approach I only provide the rods from scaffolding which only touches the surfaces of the oil tank but not connected to the it by any means. So that means, it only transfer the axial loads from the rod to the tank in order to provide the overall stability of scaffolding. These rods will not sustain any tension forces so that is it will transfer only the compression due to the lateral wind loads.

So my question is, how to model accurately those rods in SAP2000 to achieve the above described design considerations? I used the gap joint element for the tip of rods but that produces the zero displacement at the rod tips after analysis. For compression it is totally correct, since pushing the rods to the very rigid object it is quite normal to have zero dislpacement. But on the other side due to the wind load induced back and forth swaying when there is pull-out effect I don't expect the displacement to be zero then. I would expect it to be slightly offseted from the surface of the tank.

Your guidance and comments will be appreciated.

 

[JStephen]

Welding to the tank may be feasible- depends on whether the tank is being cleaned prior to the scaffold going up.
Consider wrapping a cable/ wire rope around the tank at each point. You'd still have the modeling problem you mention, but could develop some inward-acting restraint.

 

[JoeH78]

Welding to the tank may be feasible- depends on whether the tank is being cleaned prior to the scaffold going up.

Can you refer to some code/regulations/spec that those type of can be welded with appropriate necesseary precautions even if they are filled. I believe that with such a POC or reference I can convince EHS department, though I think that they will be quite reluctant for that.

Consider wrapping a cable/ wire rope around the tank at each point. You'd still have the modeling problem you mention, but could develop some inward-acting restraint.

Wiring / Cabling is quite good idea it seems that cheapest and most effective solution, I will suggest that.

So do you think that GAP joint element is correct option to model here?