Plinth Design 3

[Daverich999]

thread194-243821

Hi Engineers,

I'm about to embark on designing some plinths for some Cryogenic Plant (Nitrogen Tank, Compressors, Cooling Towers ect...).

Is there a publication (UK) which give design examples of such plinths.

I've got the Concrete Society's Technical Report 34, which gives design examples for 'Concrete Industrial Ground Floors', but I'm hoping there is some thing out there which is more specific to plinths.

Thanks in advance

 

[csd72]

A bit more information would be useful, the term plinth has a varying meaning.

 

[Daverich999]

Hi,

Simply a concrete base for the Cryogenic Plant (Nitrogen Tank, Compressors, Cooling Towers ect...)to sit on.

One of the plints will be built on the earth/original ground, while the other will be built on a existing bund.

Hope that helps.

 

[dik]

Still don't know what a plinth is... historically, it was a stub portion of masonry/stone wall at the base that broke the force of water sheeting down the wall to prevent erosion of the soil...

Dik

 

[beej67]

Maybe "plinth" means "slab" across the pond?

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[Daverich999]

Best way to describe the plinth I'm referring to is - 'a small concrete slab'.

 

[dik]

Depends on the loading, soil type and exposure conditions... any hints?

Dik

 

[msquared48]

Here in the states, "plinth" refers to a small column of reinforced concrete that is used to raise something off a slab or footing, such as the mainframe of a metal building or a tower frame.

Mike McCann
MMC Engineering
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Motivation: Don't ask

 

[Daverich999]

Hi Dik,

The Loading on the plinth will be 440KN/m^2, Soil Type is Brown clayey fine to meduim sand, the plinth will be exposed to all the elements (sun, rain, snow etc...)

The vessel that sits on the plinth has a cylindrical shape, with the base having the diameter of 3.2m and a height of 6.4m.

Cheers

 

[kieran1]

What you refer to as a plinth is more likely known as a foundation slab or raft foundation. I know of no UK publication for these elements. Just size for the allowable bearing capacity and work out the moments etc for the rebar design. Ensure you place the base at a depth which will frost heave resistant.

Some of the established industrial companies have their own standard details for these items.

Kieran

 

[hokie66]

440 kPa on that type soil will require a larger foundation in plan, or piles. You need a geotechnical investigation to determine which. Then your structural engineer will be designing either a pile cap or a spread footing, not just a plinth.

 

[stanier]

Is earthquake a consideration?

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[Daverich999]

Hi,

Kieran: Your spot on with the description. Good advice

hokie66: I believe piles may be the order of the day. I've got a geotechnical report to hand.

stanier: Earthquakes are a rarity in England, but it can be considered. What are your thoughts?

 

[dik]

Sorry for not replying sooner.

The above comments are good.

If founded on a pad with relatively low bearing values, you will be looking at a fairly large pad and possible differential deformations; a geotekkie is prescribed. It is possible to design a pad for this. If silt is present with the clay, you could be looking at frost heave problems. The foundation can be founded at sufficient depth or insulation can be used (considering the long term deformation of the insulation).

We have about 40' or so of good clay, albeit, highly plastic in our area and friction piles would normally be used. with an octagonal shaped perimeter beam, structured slab and piles. with a void under the slab (plastic clay kickin' in). We would also use a void form under the perimeter foundatio beam.

Dik

 

[Daverich999]

Thank You,

Very helpful.

 

[dik]

It's OK... I now know another meaning for plinth... it's only taken 40 years... <G>