shotcrete special inspection 2

[AlpineEngineer]

I have been requested to perform a shotcrete ispection on a thin shell concrete dome struture. The design engineer specified a 4000psi mix and shotcrete thicknesses. I was going to get a batchplant report on the mix and be on site and measure actual applied thicknesses. Is there anything else to be concerned about? It seems fairly simple to me, I think the local municpality was just nervous about it and didn't want to inspect it.
Thanks,

 

[civilperson]

Cores taken to verify the location of reinforcement is a good idea if you did not observe the use of chairs to locate the steel.

 

[DonPhillips]

IBC Chapter 17 requires special inspections and the municipality probably does not have the staff to have someone parked at the site to watch the work.

Who is testing the mix to ensure 4000 psi?

Don Phillips

http://worthingtonengineering.com

 

[hokie66]

I think the engineer who designed this work should be responsible for the inspections. Considering the number of thin concrete domes, hyperbolic paraboloids, etc which have collapsed over the years, I wouldn't want to be involved.

 

[msucog]

ask the EOR what they want you to do, how often, etc.

i would (at a minimum) do the usual concrete tests (slump, temp, etc) and make lots of notes about the placement and placement times. document admixtures or any troubles/delays experienced. i also suggest the contractor make several preconstruction panels...then core and test them. and i like hokie66's suggestion to have the design engineer there too (i'd try to at least get them there for the first few placements and periodically thereafter if possible). you might want to dig up a shotcrete inspection checklist and get the engineer to provide direction on what's needed.

 

[LittleWheels]

Make sure the fellow placing the shotcrete is experienced with the method, equipment and material. msucop has the right idea.

I've seen a lot of shadowing of reinforcement, excessive plastic settlement and other shotcrete defects during condition and structural inspections. As with most things, shotcrete isn't quite as simple as simple as it looks.

 

[AlpineEngineer]

Thanks a ton for your input guys. I found in 2006 IBC SEction 1913 some criteria. I think I have learned enough to distance myself from this thing. THe EOR is 9 hours away and is of no help, I don't think he had any buisness stamping these plans but thats besides the point. It seems like a geotech firm would be able to build the test panels and test them. As I learn more about this it sounds like an art, the gunman must have some good skills. I also read of some horror stories in failures. Not to mention this building is darn near a bunker, they will bury it with 30" of soil all the way around except for the door side, a failure could be catastrophic.
Thanks again.

 

[BigH]

You might also like to check out ACI Guides "506r 90"; "506.1r 98"; "506.2 95"; "506.3r 91"; and "506.4r 94". You don't always have to use wire mesh - you can use steel fibres.

 

[msucog]

for your own sake, i'd create a detailed paper trail of making requests to the eor. essentially show that you did what the eor required and you performed a very thorough job. if the thing fails and kills someone, an elaborate paper trail might help you (might not)...but if you don't have the paper trail, i'd say you're well on your way to being "hung".

here's some links i found while researching for one of my projects.

http://www.shotcrete.org/

http://www.concrete.org/

(search for aci 506 and/or shotcrete)

 

[hokie66]

I think your decision to distance yourself from the thin shell construction is wise. Regardless of how far away the EOR is, he should be on site for this construction. The captain has to be prepared to go down with the ship.