mast design wave load

[french44]

I have a mast in a first quarter of big LNG SHip begining 20m to 28m below the waterline ,it's welding on mooring deck completely exposed ,the ship operation area is north sea and atlantic sea,I search on rules regulations and classifications societys but nothing about this mast sorry it's a foremast navigation light and other outfit (projectors supports ). Well , i take 1.5t/m² load due to wave impact but i have a doubt is it enough ? for this ship,i read that the extrem wave in those area is 20m height but i made some sea trials in north sea and i remenber that the waves are very big...,so if you know some papers or some books . with load wave,wind load and acceleration i have 200 Mpa von mises stressed it's just ! but it's in extrem condition ,so if the wave load it's not good and increase the mast will fall on the deck ,glups
so give me your opinion

[MikeJohns]

french 44

With a large vessel you design as you would for a fixed object ie the vessel doesn't give significantly with the sea.
From your figures which look sensible I imagine the projectors will be torn off before the mast bends ? Usually best to give yourself a decent factor of safety above "just"! Re-inforse the deck well under the mast.

[french44]

thanks for ypur answer mike , my doubt is not for calculate the mast but for evaluate the load of the wave , i take 1.5t/m² but i'm not sure of that because when the boat pass throught the wave the mooring deck in under water and the wave create a impact on the mast ,i don't find in any rules this load factor ,the ship have this dimension : 300 m long ,42 m beam . 11 m draught. the mooring deck is 20 m below the waterline and the mast is welded on it .the pedestral of this mast is 600 mm for diameter and 7.6 m height.