How to Model Equipments on a Platform in SAP2000

[Marine88]

Hi,

I'm modelling an LNG platform. The model is pretty straight forward, a concrete deck, supported on steel piles, with nonlinear soil springs.
I need to model the loading arms and other equipments on the deck to look at the seismic behavior of the structural with the additional mass on its deck. How would you guys recommend modelling the top of deck equipment? I'm afraid modelling them similar to piles or other structural members may change the period of my structure. Any thoughts?

Thanks!

 

[Thanh123]

Hello,
You can buid a fiction element (like a frame but EJ very high) from supporting points to grativity of quipment, then put load at top of fiction element. I offten do this way.
BR
Thanh

 

[stressed]

You could use a rigid "dummy" element as described by Thanh, but a cleaner approach in my opinion would be assign gravity direction joint loads at the equipment center of mass and attached them to points on the deck using joint constraints, probably Body type joint constraints.

Using Define menu Mass Source you can define your mass model from loads. If the assigned loads are assigned in the gravity direction, they will convert to mass in all degrees of freedom, so this is a convenient way to account for mass of equipment and such.