Tilt up panel repair

[demayeng]

Hi, my question is whether is possible to repair a damage tilt up panel in situ..

The building is a steel portal frame factory approximately 6.2m tall at the apex, on the gable end 2 panels have been damaged by a truck impact, damage is below 2.5m height. The panels are 3m wide each and span vertically. We wer,e thinking of cutting out and replacing the bottom section by supporting the remaining top sections first, then forming up and casting the new bottom sections however I have a couple of concerns

-the cast section would not be as flat as the remaining section and would be quite difficult I assume. However replacing the whole panel is not easy because of no access for cranes etc..
- maintaining continuity of bending strength is difficult across the join.. ie starter bars.. also shrinkage of new concrete would cause a small gap at the join..


Thanks very much

 

[OHIOMatt]

Would removing the entire panels and infilling with reinforced masonry be an option.

If not, you could have the contractor remove the concrete of the damaged section and leave the reinforcing to allow for a splice. The small gap at the joint would not concern me at all. The shoring may be tricky, but a couple of holes for needle beams may solve that issue.

No matter what you do, it will look like what it is, a patch.

 

[demayeng]

Removing the panels entirely will be difficult because of limited access for a crane.. Otherwise I think your idea of full-height masonry would end up being the most cost-effective and look the best... as well as being structurally sound.

We are going to use channels on either side of the wall for the propping, with masonry anchors that can be removed afterwards

I still think pouring and vibrating the concrete right up to the underside of the remaining section is going to be difficult..

 

[OHIOMatt]

Removing the panels would not require a crane. Just some scaffold anda concrete saw. It would be labor intensive.

If you do have them cast the wall, have them add pour spouts. This will allow them to create a little head pressure and will allow for access for the vibrator. It will leave an area of concrete for cutting and patching, but it will be worth it.

 

[msquared48]

Since they span vertically, how do you plan to restore the continuity of the vertical steel in the panels if the bottom half is removed and replaced?

Mike McCann
MMC Engineering

 

[demayeng]

Hi mike,

Well that is the problem.. Matt has mentioned leaving some of the existing steel hanging out at the bottom.. But I was concerned about shrinkage of the new concrete reducing the contact at the join

Any suggestions?

Thanks

 

[msquared48]

Yes, that would work, however, I was wondering if you could avoid having to do that by installing metal tube columns on the inside of the wall to take the lateral loads, assumnig that the vertical load carrying capacity is still there.

Mike McCann
MMC Engineering

 

[hokie66]

Agree with OhioMatt. Support the broken panels on the adjacent ones, sawcut just above the damage, but not to the reinforcing. Chip out the concrete, leaving the reinforcement where required to lap with new bars below. Demolish the rest of the wall below, form up and cast new wall section. As Matt said, you can use pour spouts, or alternately, leave a gap and dry pack it.

 

[demayeng]

Ok great,

Thanks for the replies.

I did think of dry-packing, however it would look pretty ugly!

 

[csd72]

I would think that the cheapest option would be as suggested by msquared48.

 

[hokie66]

Ugly? Yes, but tilt panel buildings are ugly already. But that's only my opinion. In this case, I'd suggest you will need to coat the affected panels.

 

[dhengr]

Put some strong-backs on one face or the other to straighten in up, bring it back into plane. Depending upon the location and extent of the real damage, could you break out an area 2 or 3' high x 2' wide; skip 2' in width and repeat the break out process (another void area); maintain as much of the bottom of the panel as possible intact, to maintain bond with the steel. You can examine the steel and make some judgement about loss of prestress. Pour the voids and dry pack with non shrink grout, as you see fit, after sufficient curing time. Then repeat the process on the old panel material which was left in place during the first round, to maintain the prestress in the steel. Hopefully, the outside surface is not some exotic texture.

 

[hokie66]

dhengr,
The OP said these were tilt panels. Tilt panels are site cast and not prestressed.

 

[demayeng]

I have decided using needle beams will be easiest to gain access to the area to be worked on for removing concrete/forming new concrete etc.

What do you think of the attached sketch? I need to support the tops of the columns laterally somehow, maybe join pairs together with diagonals and struts in a bracing frame? Is there a cheaper way do you think?

Thanks

 

[hokie66]

I would just through bolt a pair of channels, say 300PFC's, to the wall above the damage.

 

[demayeng]

Yeah.. my original design uses channels, but I had SHS posts under the channels hard up against the panels, meaning they were in the way for the concrete removal and formwork.

I can either support on the adjacent panels as this new sketch shows (i'll have to justify they can work) or install SHS posts at the ends out of the way.

Each panel weighs in the order of 100 kN

 

[hokie66]

That's the way I would do it, except I wouldn't have the bolts one above the other.