Pull-In Winch Support Frame
Pull-In Winch Support Frame
(OP)
I am currently designing a steel support frame for a pull-in winch. The winch will be used to pull a 100 Tonne caisson into a production platform. The winch itself is vertically spooling so needs to be positioned directly above an opening. Hence a steel grillage is required to support it.
The pull-in condition is a temporary load case with the pull-in operation taking no more than 5 hours.
I am designing the steel using BS5950 (which is not really suitable but its the code I know best) but I have a problem with the partial factors of safety. BS5950 applied a factor of safety of 1.6 for imposed/crane loads. This is giving me a maximum moment of 1500kNm and a max shear of 1000kN. The associated stress in the member is about 180N/mm2. I could look at in terms of working stress, but I am not that up to speed with the approach (I'm an ultimate limit state man).
I would like to reduce this factor of safety in order to reduce the section size but I cannot find any guidance on a suitable figure to use for this exceedingly temporary condition.
Any suggestions or comments?
The pull-in condition is a temporary load case with the pull-in operation taking no more than 5 hours.
I am designing the steel using BS5950 (which is not really suitable but its the code I know best) but I have a problem with the partial factors of safety. BS5950 applied a factor of safety of 1.6 for imposed/crane loads. This is giving me a maximum moment of 1500kNm and a max shear of 1000kN. The associated stress in the member is about 180N/mm2. I could look at in terms of working stress, but I am not that up to speed with the approach (I'm an ultimate limit state man).
I would like to reduce this factor of safety in order to reduce the section size but I cannot find any guidance on a suitable figure to use for this exceedingly temporary condition.
Any suggestions or comments?






RE: Pull-In Winch Support Frame
One concern that I would like to point out though is that there can be significant side loads when using winches or fixed hoists. Whether intended or not side loads can result in very high stresses and should be accounted for.
Regards,
-Mike
RE: Pull-In Winch Support Frame
If I remember correctly, allowable stresses from temporary works loads can be increase by 25%, but you would need to check this.
RE: Pull-In Winch Support Frame
I am coming to the conclusion this whole assembly will be easier to check using an allowable stress code.