10-yr life design parameters

[shaneelliss]

I have been asked to design some foundations and buildings for an industrial project with an expected 10-year life. Is it possible to do anything differently for this shorter life project than it would be for a standard expected life design that would reduce the construction costs? Other than corrosion allowance or long term settlement on foundations, I can't really think of anything I can do to reduce costs. Suggestions?

 

[JAE]

You still have to meet code for strength (public safety and welfare).

But some reductions in cost from these might be possible:
1. Seismic design could look at a shorter return period which might allow a reduction in seismic loads.
2. Wind design reduced a bit but 50 year to 10 year - not much change perhaps but you could check.
3. Reduced f'c concrete strength (ACI requires 4,500 psi for exterior conc. in harsh environments - might go to 3,000 psi.



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[TLHS]

At ten years you wouldn't be allowed to reasonably reduce return periods for strength.

Maybe wind serviceability return period could be reduced.

There's some obvious durability stuff in concrete, but honestly none of it is a real cost saver.

The cost savings would be in keeping the scope tight and not building in wishlist items for a short duration installation.

There's also always the question of what happens if they extend the service life.

 

[TehMightyEngineer]

I'm thinking along similar lines to TLHS. Your biggest savings will be in eliminating extras. No need for extensive corrosion resistance. Painting and facade can be kept cheap. Roofing can be low quality. Etc.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[dik]

It's when the 10 year life is extended to 50... about the only change would be for corrosion issues...

Dik

 

[shaneelliss]

Thanks for the responses. That's about what I thought. They usually use epoxy coated rebar in all their concrete, so I told them they could probably use uncoated bar and save a few bucks but otherwise there probably wouldn't be much different. But I thought I would ask in case I was just ignorant to some obvious things.

 

[BridgeSmith]

We spec some epoxy coated and some uncoated reinforcing for bridge construction and see very little, if any, difference in price. That said, we only spec coated rebar for the deck slab, because of the potential exposure to deicing salts. All of our foundations use uncoated bars.