foundation superelements for various purposes

 

Hi

I have general question about use of appropriate waves while creating foundation superelements:

 

Psi module: What do pair of forces mean in X and Y directions

For Fatigue Analysis: Is it correct to use centre of damage wave and combine this with persistent dead and live platform loads to create superelement within psi? Then do I need to put this combination same for 1st pair (x and y direction) as well as 2nd pair (x and y directions)

For mode shapes: Do we need to use operational wave in combination with persistent dead and live loads? Again how to insert it for 1st and second pairs and x and y directions?

For seismic analysis: What operational waves to be taken into account? Is it 1 year wave? Again how to insert it for 1st and second pairs and x and y directions?

 

Many thanks.

Parents
    1. The pair of forces are for the X and Y components of the pilehead stiffness as they are calculated independently. Refer to section 2.5.1 of the PSI manual.
    2. You want to linearize the piles using the loading that will be closest to the actual loading experienced during the dynamic analysis. This will typically be the operational or 1 year loading on the structure. You can use the 0 and 90 degree waves to load the structure in the X and Y directions. The second linearization is typically not needed for fatigue analyses since the loading is fairly consistent (i.e. operational loading).
    3. If you are asking what load is to be used to linearize the piles, again you want to use loading that is closest to the actual loading experienced during the dynamic analysis. In seismic analyses, this is typically an acceleration that is applied to the structure that will closely match the acceleration due to the seismic spectrum. This can be an iterative process since the true acceleration will not initially be certain. You can use 0 and 90 degree accelerations to the load the structure in the X and Y directions. The second pair of load cases is intended for a second intensity seismic event, so that you can have an operational and/or extreme seismic event.

    Regards,

    Geoff

  • Thans Geoff.
    In order to get the linearised foundation for mode shape extraction for seismic analysis, what load cases should I consider? Is below appropriate:
    Dead Loads
    75% Live Loads
    Wave Load (?? year storm)
    Current Load (??)

    Please suggest what would you do?
    Thanks.
  • If you will refer to my previous post, I suggest using an acceleration instead of environmental loading because that will more closely match the seismic loading.

    Regards,

    Geoff

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