How to determine Lateral torsional loading

[Bogster]

I am currently working on a drilling project which plans to use a steel template subsea to accurately locate well locations on the seabed.

The steel template is to consist of four cylinders (1m dia with 25.4mm wall thickness and 1m in height)interconnected with a universal beam (serial size 0.914m x 0.419m). The four cylinders will be spaced out equidistant from each other at 4m intervals. Overall length of the assembly is 12m.

The assembly is to be supported at one end and therefore will act like a cantilever.

It is planned to pass rotating components through the cylinders in a vertical direction and there is a possibility due to the tight tolerance that they could bind on the cylinder creating a torsional load in the horizontal plane of the assembly.

Question is will the torque be transmitted directly to the suppport at the end of the cantilever or will it have to overcome the weight of the assembly from the point of torsional loading to the cantilever support?

Hope this wasn't too confusing. Thanks for any help

Rgds

Bogster

 

[ishvaaag]

As long as the binding action at one side pushes downwards and upwards and is eccentric it will generate some amount of torsion in the cantilevered beam, the amount of which maybe is to be estimated through structural analysis of the whole 3D contraption (schematic, i.e., lime members) and likely by imposed deformations caused by the drilling equipment, the actual expected the better if known, if not an estimate.

Of course for a detailed analysis you will count the selfweight of the structure, but since this (other than the attached cylinders maybe) is centered it means no thing to counterbalance any imposed torsion.

So it is a matter of taking the efforts produced by the analysis and verify all is OK, or else change again.

 

[desertfox]

Hi Bogster

If I understand correctly your set up ie:- 4 cylinders in a straight line connect by a universal "I" beam ?

I would just raise the point that "I" beams are not very good with torsional loads and a better shape would be a closed section like a tube , rectangle or square. In response to your question, shear stress due to torsion would be present along the beam length and maximum deflection would occur at the point furthest from the support.

As these tubes your supporting on a cantilever are quite heavy have you allowed for the vertical deflection of the cylinders due to self weight when determining clearance for the rotating components to pass through the bores?


regards desertfox