# Effect of waves on offshore moored barge?

1. May 19, 2014

### Makis

Hello PF members,

I would like to ask you a question regarding offshore moorings for barges up to 100 meters. More specific, I have a wave moving with 4 m/s and 3 meters height.
The dimensions of the barge are:
Length= 100m
Depth= 7m
The barge is moored with a line and the line is anchored on the seabed.
My question is, how can I calculate the effect of the wave on the aft surface of the barge (subsequently, to the whole body)? And, how this whole 'power', effects the line (thus, tension) and following, the anchor on the seabed?
I know that my question is a bit weird but I hope that you got the point of what I am trying to find :D !!!

Thank you in advance,
Makis

2. May 19, 2014

### SteamKing

Staff Emeritus
Naval architects and ocean engineers perform mooring analyses of the type you asked about in the OP all the time, but the calculations are not simple and are usually done with the aid of special software. You probably can get an order of magnitude estimate of the forces involved with a few hand calculations, but this is still a complex problem to analyze in such a fashion, particularly the catenary effect of the mooring line, which is non-linear.

It's not clear what you mean by 'the effect of the wave on the aft surface of the barge'. The moored barge is going to surge, heave, sway, roll, pitch, and yaw in the seaway depending on the direction of the waves relative to the barge, and the catenary in the mooring line is going to add to the hydrostatic restoring forces and moments of the barge hull. The mooring analysis will determine the magnitudes of these forces on the barge and in the mooring line, so that you can determine if the anchor point of the line to the bottom has adequate strength.

3. May 20, 2014

### Baluncore

Offshore, but how deep is the water?