estimating soil stiffness in FEM for modal analysis

[airborne12]

Hi,

For a project i have to analyse the first eigenfrequencies for a windturbine placed on the sea bed. Problem: how do i model the influence the stiffness of the sea bed. My first guess is to model the stiffness with springs. WHat is a good first estimate of the stiffness of the seabed? Where can i find references?

thanks

 

[fndn]

If you're looking for k values, you may estimate it as q/s. You may use q(stresses) in psi value and S(strain)in inches.

As for literature, I haven't seen any lately.

 

[jdmm]

As an old fart,

I would say that your problem does not fall into traditional simple problems of lack of knowledge. This is an area that may require further investigation by your client depending upon the importance of the question.

Don't even try a first estimate. You are not doing any favours for your client. It is the responsibility of your client to determine important parameters. These are the things that advance the knowlege in engineering.

jim

 

[billsumner]

I must agree with jdmm. Leave it to soils engineers.

Soils are not manufactured materials like steel or aluminum.

Their properties vary a lot both vertically and horizontally.

When you apply oscillating loads to them, such as from wind turbines, their properties change over time.

Refer to the recent ICE Geotechnique publications where Can or Suction Anchors have been tested for turbines in sands and clays.

 

[naitwerk]

I have been having problems getting the right formular to calculate modulus of subgrade reaction k,(spring constant in N/MM3).-in newtons per cubic millimiter.can i get help?