dummy girder for the erection of plate girder

[zohl]

I am designing a dummy girder to provide for overturning stability of a 60 m offshore plate girder. I need to know the forces (vertical & lateral )resulting from this process.

 

[Lomarandil]

I'm suppose you mean as temporary bracing until the permanent bracing mechanism is installed?

If you're working from US codes, you would analyze the 60m plate girder, determine where that needs to be restrained (and restrained in what axis) to assure stability under self weight (plus some destabilizing forces due to environmental conditions, pitch or tilt of any supporting vessels, erection methods, initial imperfections, etc.). Then design the dummy girder such that it has enough strength and stability to provide that restraint per AISC Appendix 6.

The quick and dirty answer, exclusive of any offshore-specific information, would be to brace for 2% of the compressive flange force as a lateral load.

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just call me Lo.