Tilt Up Panels - Bracing and Lifting shop drawings

[NFExp]

I recently did a simple tilt up project. I specified the lift design was to be designed by others and signed and sealed by a delegated engineer. The contractor has submitted some shop drawings that are not signed and sealed. Before I reject them, I was hoping to get some feedback from the engineering community.

Also, the shop drawings included bracing drawings. The bracing was not addressed in my drawings. I am hesitant to assume the liability for the bracing. Let me know your thoughts.

 

[phamENG]

Before I reject them, I was hoping to get some feedback from the engineering community.

What sort of feedback, exactly? The necessity of signing and sealing delegated designs? What exactly did you delegate? The design of the panels? Delegating the lift plan makes sense - but the design of the panel for lifting should be completed by whoever designs the panel for everything else. Lifting is just another load case that will stress the same rebar that in-service wind load will stress. Whoever designs the panel should absolutely be a licensed engineer...

I am hesitant to assume the liability for the bracing.

So don't. I'm assuming you're talking about temporary construction bracing? Don't comment on that section unless it looks grossly under sized. Make a note that "temporary works are part of the contractor's means and methods and have not been reviewed" or something like that. Now if they have an 18' 2x4 holding up a 12" thick wall and you don't say anything, your head would likely roll when that toothpick snaps on account of gross negligence. But if the sizes are even remotely reasonable then temporary bracing wouldn't be on you.

 

[JLNJ]

Sometimes these delegated design places shoot a submittal out before they have someone in hand to do the sealing. They like to resubmit a final FINAL set under seal. You can at least check to see that they understood your design intent.

If you are concerned about liability, mark on the submittal exactly what the delegated designer is responsible for and ask for a sealed resubmittal.

 

[NFExp]

Thanks for your responses.. WE designed the panel (thickness and rebar) for wind and gravity as required for this area. We did not consider the lifting stresses and followed the recommendations from TCA (Tilt-up Concrete Association) which recommends that specialized vendors design the lifting and bracing. My understanding is that the panel rebar is neglected for the lifting design and only the concrete uncracked flexural stress is used. The concrete stresses are controlled by the number and spacing of the inserts.

I'll review the lifting drawings and confirm that the panel sizes and weights are shown correctly and I will request the final lifting drawings be signed and sealed.

 

[JStructsteel]

We always designed, detailed rebar and lifting locations. Why not keep that money in house?

With that, we tried to be uncracked for stresses. Either a 4, 6, or 8 point lift.

 

[Once20036]

In the steel industry, it would be unusual for a specialty engineer to sign and seal a set of shop drawings. Typically they would sign a seal a calculation package that they prepared.
AISC also requires written confirmation that they have reviewed the shop drawings and confirmed that their connections are accurately depicted. Maybe something similar is at play here?

I also wouldn't review bracing shop drawings "filed for record only" is my go-to response.

I surprised you say that panel rebar is neglected for lifting design. I haven't heard that before.
I`m accustomed to seeing the reinforcing considered, and additional bars added if needed, based on the geometry of the lift points.

 

[dylansdad]

In every tilt wall building I have done, I have designed the panels only. I have delegated a third party to locate the lifting points, bracing points, and additional reinforcing or strong backs for lifting stresses. This third party has also supplied the braces and lifting hardware.

 

[Brad805]

It is very common that the design of these panels is governed by lifting stresses. I suggest you check that unless the GC is responsible for the complete panel design. I would pick up the tele and talk to them to see if they have an engineer and will be providing sealed shops.

 

[Aesur]

We always designed, detailed rebar and lifting locations. Why not keep that money in house?

Because 99.99% of the time the owner doesn't want to pay you up front for this, so there is no "money" for the EOR to design said items, these are almost always in my experience deferred and rolled into the construction loan through the contractor. Typically I see the lifting design engineer adding additional bars where needed for their lifting design.

 

[Brad805]

I think delegating is better in this case. Unless you know the equipment, work sequence, and logistics of the site it is not very likely the EOR will detail this very well.

 

[phamENG]

I think delegating is better in this case. Unless you know the equipment, work sequence, and logistics of the site it is not very likely the EOR will detail this very well.

For design-bid-build, I agree. But the couple times I've been involved with one of these I delegated the entire panel. Trying to do my rebar design and then incorporate somebody else's rebar and who is responsible for what and why is it so congested just didn't seem worth it. The precaster's engineer can just run a few extra load cases...

Did a site-cast tilt up once and I did design everything - but it was also a design build and I was able to work closely with the contractor.

 

[EZBuilding]

Agree with the general consensus - panels either fully delegated or primary design by the EOR and additional design by delegated engineer for the lift case and bracing.

One comment I made on a review of the bracing design - the delegated engineer was bracing the panels back down to the 4" wire mesh reinforced slab on grade and performing no calculations on the capacity of the slab to resist the tension loads.