Midship Section & Bending Moments

Hi everyone,
I have had a quick look around the forum looking for information on checking the longnitudinal strength of a vessel without any luck. I was hoping someone on this forum could point me in the right direction to gather more information on calculating still water bending moments & utilizing this to check that the midship section of a monohull vessel is strong enough to resist these forces.

Thanks in advance for all your help.

Cheers,
Sean

 

Check http://www.eagle.org/rules/downloads/under90/Part 3_e-June04.pdf

Chapter 2 section 1 Longitudinal strength.

This is only one example. You should check regs for your kind of ship.

NB: Still water may not be enougth since typically a ship moves on a wavy surface.

 

Sean,

Principles of Naval Architecture, available from the Society of Naval Architects and Marine Engineers, has a thorough description of how to calculate hull bending moment. It begins with the weight of the vessel, less its buoyancy, all distributed along the length of the vessel, to determine the final load of the hull. This load distribution is then integrated twice to get first shear loading, then the bending moment. From the geometry of the ship structure, you can calculate the hull girder moment of inertia and section modulus at any point along the length of the hull. Dividing bending moment by the section modulus at any position gives you the stress in the structure. Dividing bending moment by Young's modulus x moment of inertia (ExI) and integrating twice more gives the deflection of the hull (hog or sag). For cargo ships, this process must be completed for each cargo loading condition.

Eric

 

Thanks

Hi fcfc & Eric,

Thanks for both your responses.
The vessel I am looking at is made from aluminium and isn't long in length 11m and is a hard chined vessel with fewer transverse frames & longnitudinal stiffeners and increased plate thickness. So I just want to check that it's longitudinal strength is sufficient.
I have been putting off buying the PoNA, this just gave me another reason to buy them sooner rather than later.

Thanks again for your responses,
Sean