What about lashing loads?


#1

I am trying to figure how the deck loading is calculated on GOM work boats. If the deck is rated at 600 lbf/ft^2, what exactly does this mean?
Is this the static load of the cargo on the deck? Is it the maximum loading for the deck, meaning that dynamic forces need to be computed? What about lashing loads? I was under the impression that the load rating was for static loads and the dynamic and lashing factors were included in the calculations.

Thanks


#2

It’s just static load.

Curious why so you need to figure out dynamic and lashing loads?


#3

I’m guessing he’s taking some really dense cargo and wants to make sure he’s right that the max deck lead is as simple as taking the square footage of the cargo, multiply by 600, and if it’s less than that he’s good to go. Yes, it’s really that simple.

If you try to refuse based on deck load you’ll probably get push back saying that the deck boards distribute the weight, making the cargo footprint bigger, so you’re safe to carry the load (I consider that argument bullshit unless the equipment is barely over the limit).


#4

The rated deck load is quoted for uniform load distributed globally. If the cargo is such that the point load exceed the rated load per sq.ft./sq.m. some form of dunnage/cribbing has to be used, or grillage constructed, to spread the load over the area required to stay within the allowed limit.

Here is cribbing laid out on deck of a Heavy Lift Vessel to spread the load evenly on the bottom of the cargo. (No problem with load factor on the HLV deck):


In this case the cribbing is in a “fish bone pattern”.

Here is a more common way. This to ensure that the load is distributed on the frames of the cargo, not on the bottom plates:


This is from loading a jackup rig on HLV Black Marlin

The same basically apply in reverse when loading heavy cargo on deck of an OSV, Barge or whatever.
If you cannot spread the load on sufficient area, make sure point load gets on the frames.

PS> if there are wood cladding on deck, check if the rated load take this into consideration.

PPS>If you need to weld lashing pad eyes on the T- bars for the wood cladding, make sure they are full welded to the deck. (Sometimes found to be only tack welded)