# Maximum Permissible Load On Deck

Discussion in 'Class Societies' started by naserrishehri, Jul 11, 2013.

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### naserrishehriSenior Member

dear friends
how can i calculate maximum permissible load on a small region on deck
while i have structural drawing in that region ?
can i consider that region as a simply support beam and put load on it?

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### gonzoSenior Member

Are you also considering stability?

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### TANSLSenior Member

As Gonzo sensibly says, you must take into account the stability.
However, the answer to your question is not that, but yes, you can calculate the way you say, bearing in mind several things, for example:
- Also consider the associated plate of the beam when calculating the modulus of the beam section.
- If it is a point load or uniformly distributed load on a surface?.
- Take into account the associated plate surface to calculate the actual load per m2 on the beam.
- Is normal considering a fixation on the ends closest to the "fixed" than the simply supported. To this must be achieved, for example by brackets, that the ends are fixed (not rotation possible).
- You have to decide if the beams are to be "supported" by the girders or vice versa.
- Sometimes to not increase too much scantlings of the beam, to reduce its length, it is good to place intermediate pillars.
Well, the solutions to problems that arise will take you as you like.

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### naserrishehriSenior Member

I have already considered stability .

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Would be nice if you could post the structural arrangement, then it is easier to state which and why.

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### naserrishehriSenior Member

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• ###### LOAD CASE PLAN Model (1).pdf
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I was thinking more of a sectional view to see how the structure joins other structure and how it ends. As this dictates the fixity. However it "appears" that the beams are continuous and fixed at the ends from the ‘simple’ plan view. Thus assume built-in and then work backwards to find the load that produces a stress equal to the design allowable and then double check for deflection to ensure it is not excessive.

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### TANSLSenior Member

naserrishehri, If you want help, it would be good that you detailed some things:
- Material of the structure.
- Thickness of the deck.
- Built-in or supported ends of the beams?
- What do you want to know ?:
- The maximum weight that can hold the deck
- If the deck can withstand the 40 tons container​
The deck, without doing any calculations, seems extremely reinforced: beams with big section modulus and short webframe spacing.

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### naserrishehriSenior Member

i want to calculate permissible deck load per square meter and issue to class .

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### TANSLSenior Member

In addition to the data I have stated before, you need to know the maximum strenght allowed by the Classification Society, when it is a direct calculation.
Then you do the process in reverse: you know the sigma and the modulus of the beam. You can calculate the maximum bending moment in the beam and thus the maximum load/m2 that deck can support.

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### gonzoSenior Member

I mentioned stability, because as the vessel heels over with an increased load, the direction of the force vectors changes. That affects the calculations.

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### TANSLSenior Member

Gonzo, you're right. It appears a new component of the force in the direction of the beam, while the perpendicular component to the beam decreases. There are a number of new effects on the structure.
But this has nothing to do with the stability of the ship, unless there is a shift of cargo. But the solution for this new problem is not to increase the scantlings of the girder.
Do not confuse nasserrishehri. It is better to clearly answer what he asks and not speculate.

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### naserrishehriSenior Member

dear TANSL
please clarify for me , how you simplify deck structure by a beam and calculate
permissible deck load if possible .

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• ###### page-4.pdf
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### TANSLSenior Member

See attached file

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• ###### Deck Beam.pdf
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### naserrishehriSenior Member

Thanks A Lot TANSL .
Now i have calculated P=20 ton/m .how much is P(ton/m^2) ?

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