Tilt Wall Footing Design - Point Loads

[BadgerEngineer]

My understanding of how a tilt wall panel should be properly set in the field is the following:

1. The panel is raised and set on shims (on a footing) by a crane.
2. The panel is held until the gap between footing and bottom of panel is grouted & grout is set.
3. The panel is braced and crane removed.

Is this typical practice? A GC is using a different method that inolves setting the panels on shims, bracing, then moving to the next panel before grout is set or before grouting at all. He states it is not economical to wait for the grout to set which I understand.

The prob with this is that the footing no longer acts as a continuous wall footing. It is now point loaded at shim locations (Approximately 4' o.c.) They are seeing cracking in the footing as a result of this.

The GC is stating this is standard practice and tilt wall footings should always be designed for this type of loading. Does anyone have any experience with this? Right now are current solution is to decrease shim spacing to allow the load to be distributed more evenly.

I appreciate all your input.

 

[csd72]

in my experience it is typical for the grout to be placed afterwards.

No matter what you do, the majority of the load will actually be on the two shims regardless of the crane holding it.

To make things more difficult it is actually very hard to get the weight distributed on more than 2 shims per panel.

I would suggest you look for a tiltup or precast handbook as a reference for the accepted practice.

 

[DaveAtkins]

I have always designed for the point loads.

That being said, the wall panels are not very wide, and you have two shim locations per panel. So I am wondering why the footing is cracking. Is it cracking in bending between shims? At the shims?

DaveAtkins

 

[BadgerEngineer]

These are actually very large/heavy panels. 35' high & 10" wide. (I would have to double check the max spans)

Are you stating you should never use more than 2 shims per panel regardless of span? And if so, is there a max suggested span for tilt panels?

I've referenced the tilt up manual I have, but it has little information on this topic.

 

[structuresguy]

This is the typical construction sequence that we see on all our tilt jobs. (and we do lots and lots of tilt)

We require them to grout under the panels before the floor slabs are poured. That way, they can erect internal framing, and deck the floors to provide an adequate diaphragm to brace the panels, and then remove the temporary bracing. But the panels need to be grouted before the concrete floor slabs are poured.

We have never heard of our wall footings cracking due to the weight of the panels sitting on shims, which are also typically at 4 ft spacing. We don't provide top steel in our wall footings for shim loading. We only provide top steel where there might be negative bending in final configuration, such as at large openings. Our typical wall footing for tilt would be 2-4 feet wide, and 16" thick, with 3000 psi concrete, with minimum shrinkage steel (0.0018*Ag) continuous along the bottom.

Is the cracking regular spacing, or limited to one area? Is it possible that they drove the crane over the footings, and damaged them? We have seen that happen many times before. Other than that, I would say you have a soil bearing problem. Did they have adequate compaction under the footings?

 

[csd72]

I have done quite a number of panels in excess of 35' and with thicknesses up to 10" and I have not had a problem with the footings cracking before.

Every site I have been two has used 2 shims per panel.

What type of cracking are you talking about?

 

[hokie66]

I would also like to know what type cracking has been observed. What is the pattern? The most common type of cracking in footings is plastic settlement cracking around the top bars due to inadequate consolidation.