scantling calculations

[abhishek]

how can we arrive scantlings for tugs with IRS RULES (ie) INDIAN REGISTER OF SHIPPING FOR 10 TONNES BOLLARD PULL TUG

[Ad Hoc]

Firstly
You need to establish the safe working load, ie what factor of safety you are going to apply to the 10 tonnes. So, is it being used daily, once a week, once a month, once a year etc??..this determines the factor of safety you use. Anything form 3 up to 6 or more. (UK MoD use 9)

Secondly
You need to design it, that is draw, the bollard. You then calculate what section is required to withstand the 10 tonne load, plus the FoS. For bending (if any) and shear.

Thirdly
You need to establish the load paths...ie what structure is there on the deck and under the deck, to take this load.

[PAR]

They need to hire someone capable . . .

[abhishek]

can i have some formulas to find out the loads and what are loads acting on the tug.

[Ad Hoc]

Providing formulae wont help you unless you understand them; from my post above, this does appear to be sadly in evidence already. However, if you understand them, then you should be capable of deriving a formula of your own from simple momentum theory.

If you cannot do this, then i suggest you employ a naval architect that can do it for you...since you are asking some very very basic and fundamental questions of design that any professional naval architect can do.

[abhishek]

thank you Ad Hoc sir, i am a naval architect, i know the static and hydrodynamic loads acting like wave induced bending moment and shear forces and still water bending moment which can give the total bending moment and the ships own weight with its buoyancy, vertical and horizontal bending moment with hogging and sagging ,but rather than these if any of the loads should we consider ? but this is really nice to share every idea ...

[Ad Hoc]

abhishek
"..but rather than these if any of the loads should we consider ?.."

It is your boat. Only you know the SOR and duty of the boat no one else. That is therefore for you to establish where the possible loads shall come from, and then as a final check look at the Class requirements.

If you are a naval architect and you understand how to calculate structures, then my post #2 provides you with the solution. I can't be any clearer than that on such limited information.

[abhishek]

ok Ad Hoc sir thanks for ur reply..........

[gonzo]

The rules should provide you with what you need. They usually specify all that

[abhishek]

thanks for all the senor people especially Ad hoc sir , i have one doubt regarding the bending moments as the tug goes only in restricted ares like shallow waters only should we consider the still water bending moments and wave induced vertical or horizontal and hogging and sagging moments for calculating the scant lings.

[Ad Hoc]

You have to first look at the specification of the boat. What does it say for Class notation? Then look up the Class notation and see what structural calculations, by Class rules, are required.

It matters not whether the boat is in a river a lake or the deep ocean. You need to establish the "area of operation". From this the global loads can be established, to apply to your boat. If you are stuck, then Class rules, which you must comply with, with have the answer for you.