Seismic Design of Internal ground supported Piperack (Non-structural or Building design?)

[EireEng]

Hi All,

We are designing a large internal ground-supported piperack structure for an industrial facility located within Europe in a seismically active region,
The piperack system carries mechanical piping and electrical cabling and is a sizeable structure,
There are 15No. piperacks located at the ground floor level of this single-storey structure.
Each piperack structure is approximately 60m in length and the piping on the 15NO. racks bridges between each rack also.
The racks are designed with modular offsite construction in mind and a light-weight steel frame carrying the services will sit on top of hot-rolled structural steel framing beneath, with columns spaced at approx 5.0m centres, the racks are circa 7.0m in height

My query is this;

When assessing and designing this structure for seismic design requirements;
Is it sufficient to design the frames of this rack system as a Non-structural element supported at ground slab level in accordance with EN1998 or should the design of the structural steel frame be undertaken as if the steelwork was a building structure (essentially an unclad steel building supported from a raft foundation (ground bearing slab))
I believe the resulting foundation forces will be considerably different dependant on which option is chosen

Any thoughts on this would be appreciated

Regards

 

[saplanti]

Everything depends on how you are going to transfer structural loads on to civil engineer to design the foundation.

Just be careful about the differential settlement of columns and implication on to the piping on the rack. Therefore I would discuss the issue with civil engineer about the foundation type and expected load information transfer to design foundation/slab.
If pipe stress engineers can manage the settlement in the calculation, this could be end of it. But you need to take pipe stress engineer into discussion for the positive outcome for all parties.

To be able to reduce acceptable settlement, you may have to be forced to use single block foundation with/without piles (becomes more complex with weak soil types). In this way you may consider differential settlement between neighbour slabs only, not for piping on a single block foundation.

Piperack is a steel (in your case) structure with high masses elevated.

When you start discussing the issue with these parties you will find more content to consider in addition to cost.

I hope I did not confuse you with these, but your answers will be clear on the discussion with these parties.

 

[EireEng]

Hi Saplanti,

Thank you foryour reply. The foundation (supporting slab) will be designed to manage the settlement (both differential and total) so as to not adversley affect the piping/joints on the rack. It is the determination of the reactions that I am interested in based on the appropriate seismic analysis method.
Thank you for your reply again,

 

[saplanti]

You need to check the code that you are supposed to work with. You may be able to use the equivalent static or dynamic analysis depending on the natural frequency of entire system, I guess. I trust if you follow the code you will find out.

 

[GC_Hopi]

In my region we would generally use the classification called "non building structure similar to buildings". If you do not have a such a classification then you could investigate both paths to see what the difference in the reactions would be since that is your area of interest then make a judgment on what is most appropriate. Also see if there are any local experts that can advise you and what is the owners preference/input.