rotational lift calculation .. urgent
rotational lift calculation .. urgent
(OP)
Hello,
I am enclosing a steel structure which weighs around 30tonne . need to find out if the 2 highlighted corner structure can handle a rotational lift of the steel structure from horizontal to vertical. What method can I use to find out if those corner structures can withstand the load. normally padeyes are used but i just want to find out if in any critical cases, instead of padeyes can they use the corner structures highlighted for a 2 point rotational lift. Can I use FEA/ any methods/ hand calculation, if its FEA what sort of boundary conditions can I use and where? Any help would be much helpful
Regards
faber
I am enclosing a steel structure which weighs around 30tonne . need to find out if the 2 highlighted corner structure can handle a rotational lift of the steel structure from horizontal to vertical. What method can I use to find out if those corner structures can withstand the load. normally padeyes are used but i just want to find out if in any critical cases, instead of padeyes can they use the corner structures highlighted for a 2 point rotational lift. Can I use FEA/ any methods/ hand calculation, if its FEA what sort of boundary conditions can I use and where? Any help would be much helpful
Regards
faber






RE: rotational lift calculation .. urgent
to calc the force applied, i guess you'd look at the work done by change in potential energy of the weight, and the distance the corner moves and this (i think) will give you the force required. now you can do a free body of the strucutre (at an angle) with the lift force applied, the weight, and the ground reaction. then it should be a "simple" analysis to find the internal reactions in the structure.
remember to apply whatever safety factors are required.
RE: rotational lift calculation .. urgent
BA
RE: rotational lift calculation .. urgent
Rotational lift is 90 deg from horizontal position to vertical. It just to make the sleeping structure to stand upright. I just want to find out if those corner structures as highlighted in the figure can withstand the load. It will be held only in 2 positions as the padeyes initially fixed have been removed.
thanks
RE: rotational lift calculation .. urgent
mind you no-one will say "yea" or "nay" based on your very simple sketch. what sort of detail structure is in the corner ? (full weld i suspect) what sort of load has the strcuture been designed for ? (much more than self weight, i suspect) if the strcuture was designed for lifting eyes, you'd've thought that the designer would have considered this case. if the designer knew that the strcuture was going to be assembled horizontally, and then erected, you'd've thought he'd've considered this.
is someone (structurally intelligent) querying the design, or is this "just" a box being ticked ?
part of my original post was you need to be concerned about more than the two corners with the eyes.
RE: rotational lift calculation .. urgent
When it is directly over the right hand bottom corner, the entire weight will be on the ground and the lifting force will be zero.
If the center of gravity moves to the right of the bottom corner, the structure will lurch to the right unless prevented by some external means. So you need to have cables attached to slowly ease the structure into a fully vertical position.
BA
RE: rotational lift calculation .. urgent
RE: rotational lift calculation .. urgent
RE: rotational lift calculation .. urgent
RE: rotational lift calculation .. urgent
The worst case of load occurs in the two corners diagonally opposite the circled corners because they must sustain the full 30 tonnes when the c.g. is directly above them. As the c.g. moves beyond that point, the lift force starts to increase. It reaches 15 tonnes just before touchdown.
BA
RE: rotational lift calculation .. urgent
BA has made a very good point ... make sure you have some "preventor" straps to slow the structure once the CG is right of the ground point; ie make sure you can slowly lower the structure.
and make sure you brace the ground point (that you're pivoting about), so that the whole thing doesn't slide to the right !
it sounds like the structure originally had eyes attached, but now it doesn't. how close are your shackles to where the eyes were ?
how did you get the structure lying down ? (i assume that some time recently it was vertical ?)