Masonry wall out of plumb 4

[SteelPE]

I have a project that I am working on that is currently under construction (IBC 2015). The building is a single-story masonry bearing building supporting open-web steel joist and metal decking. Steel erection began last week and today I was told by the steel fabricator (who I work very closely with) that the masonry wall is out of plumb over 120’ of a 300’ long masonry wall. The wall is quite tall 29’ and I have been on the GC from the beginning about proper construction of the perimeter walls.

I don’t know exactly why the wall is out of plumb. I am guessing it wasn’t quite properly braced as during my last site visit, I found a large brace that wasn’t anchored to the deadman. It is in this area that the wall is out of plumb.

How do you go about fixing a masonry wall that is out of plumb? I can’t say that in 20 years I have ever had this happen before.

The out of plumbness is causing joist bearing issues on the wall (which is how this error was picked up).

I am not exactly thrilled at the moment.

 

[r13]

Since the deflection is affecting the proper bearing for the joist, it looks like some masonry re-work is required to correct the problem. The tricky part is to determine how much works to be removed and redone, and how much you want to shield the contractor for the burden he is obligate to bear. A good measurement should be the first step towards finding a good/reasonable solution.

 

[darthsoilsguy2]

the last time i had an out-of-plumb wall... my speculation was that they were grouting too soon after it was being layed and they were only checking plumbness on the new work and not the post-grout work below.

 

[BAretired]

A 29' high by 300' long wall is a very large risk to leave exposed to the wind for a long time with only temporary bracing. The danger of blowing over is a factor to consider even when bracing is carefully installed.

If the out-of-plumb distance is not too large, the contractor may be able to ease the wall back to nearly plumb condition using cables and ground anchors each side of the wall. A 29' high wall should be fairly flexible, but it would be exacting work and should be followed up with joist attachment as soon as possible after or, better still, during the plumbing operation.

BA

 

[SteelPE]

Well, it's the next day and I'm still not thrilled (after a sleepless night).

I think we need to figure out what exactly is wrong in the field. Is the whole wall tilted, it the last course laid wrong, is there something else going on that we don't know about.

I am sure the GC is going to pursue easing the wall back (pushing the wall back). At that height I don't think it is going to take much force. I just want to know what options are on the design end before we have a conversation with the GC.

I was very skeptical at the beginning about building these walls. We have done another wall of this height with the GC in the past without incident so I knew it was possible and they were capable, but I still didn't like it.

 

[r13]

I am not so confident on the strength of the wall after straightening by force, will all the bond remain unaffected? Also, how thick is the wall?

 

[BAretired]

Wall thickness and reinforcing might help as well as a rough plan of the building showing interior column lines and shear walls or lines of permanent bracing, if any.

BA

 

[SteelPE]

Wall thickness is 12" (we just met the h/t requirement of 30 in ACI). The overall building is 600' long with an expansion joint about in the middle with a concentric steel brace along each side of the joint. No perimeter columns along this wall. The perimeter walls act as shear walls to resist lateral loads (since there was miles of masonry around the perimeter).

From talking to the client today it appears as if this is an isolated issue (withing 1-2 panels of masonry). I was told 9 joists do not have proper bearing (so that is 45' in-between those 9 joists). They are not exactly sure what went wrong yet as they are still trying to figure it out. The wall is way out of the 1/2" tolerance specified in ACI.

I suppose I could go back and check the wall for additional eccentricity. If I remember correctly, axial load was as much of a concern as bending (we specifically detailed joist bearing to fall within the h/t requirements of the code). I don't want to be the one to "fix" this form them. Their problem should not become my problem.

 

[Brad805]

I think how easy it is to flex back will depend on how much steel is in place. If little steel is installed, and you have bond beams, I would rent some meadow Burke braces and slowly rotate back. That is assuming the it is a simple case of some accumulated errors and not some real sloppy work.

If you really want to know how far out the wall is hire a 3D laser scanner company to scan the wall. We do this type of work with our 3D scanner, and it is easy when it is a clear open space. It could be as little as one scan where it will take longer to setup than do the actual scan. Our scanner will collect data from as far as 1100ft in the right conditions. When done, they can give you a file that shows you the true wall shape within mm's. I will post a couple of screenshots shortly of a floor slab and wall structure we did not long ago.

 

[Aesur]

I'm surprised they even braced the wall, in my area I see CMU walls that tall being built all the time without any bracing. With what ever decision you make, keep in mind that you accept a great deal of liability if you let them rotate the wall back rather than rebuild it.

 

[SteelPE]

Steel is installed but not physically attached to the wall yet. They realized they have and issue so the roof members have not been attached to the wall. They have a style of Burke braces installed in the field as temporary shoring already. We did place bond beams at window head, mid height and under the joist bearing (which works out to the 1/3 points of the wall).

Out of curiosity, I went back into my computer models and modeled the eccentricity of the new wall on the applied dead and snow loads (using the eccentricity on the full dead which isn't quite right as the weight of the wall is a large portion of the dead load). After a 5 minute heart attack (forgetting how the NCMA software works for 5 minutes) it appears as if the wall has sufficient reinforcing to resist the as-built eccentricity.

I don't know what I am going to do. I want to see if the GC will come up with a pleasing solution (doubtful). I am sure this will not be resolved until sometime next week. Until then I will ponder the options.

 

[Brad805]

Here is an example scan as mentioned. Keep in mind this is not a picture. The scanner creates colored points and collects enough points that the data looks like a photo when done.

From the data you can create a contour map like the one below.

This was one of the worst slab on grades we have scanned. It has heaved over 9". Here we could use a contour interval of 1"'s and not 1/8 ths like typical.

 

[phamENG]

Brad - that's pretty neat. What kind of scanner is your company using, and what kind of file output does it deliver? What about post processing requirements?

 

[Brad805]

We are using a TopCon GLS2000, but would like to upgrade to the new Leica RTC360. Leica and Faro are the more common scanners. Registering scans together can take some time if you have lots of scans, but the new RTC does a pre-registration as you are scanning since it tracks the scanners position. We hope that will speed up the process of registering the data. The scanner is essentially collecting million of points, and 360deg photographs. The points are colored automatically based on the photographs. At the end of this you have a point cloud that can be read with Autodesk Recap, imported into Revit, CAD, or many other packages that can handle very large point files. The top image was taken from the Revit model. Converting the data into a solid model after this can be tricky. There are endless software solutions for different aspects, and you may require many software packages when involved in multiple industries. In a case like this one could easily figure out the wall deformation by measuring in Recap to find the wall bow.

There are some other nice scanner solutions on the market too that are much more cost effective. The progress being made in photogrammetry is quite impressive and it is quite a bit easier to work with. The Leica BLK360 can collect data that can be accurate to within 1%. This would not work well for this case if dealing with long distances, but if you are wanting to create decent general arrangement drawings for a reno, it can be a great option.

 

[XR250]

What about welding extensions on the bar joist seats? I guess cutting the metal deck and massaging the edge angle to conform to the bow could be a bummer.

 

[BAretired]

29 May 20 18:31
I'm surprised they even braced the wall, in my area I see CMU walls that tall being built all the time without any bracing. With what ever decision you make, keep in mind that you accept a great deal of liability if you let them rotate the wall back rather than rebuild it.

Would the masonry contractor's insurance policy cover an unbraced wall if it blew over in a 30mph wind?


BA

 

[dik]

BART... I don't think I've ever seen a masonry wall built that high... on a positive note, if it can be restrained by the roof diaphragm, it takes little force on 29' to hold it in place... might not be that difficult a problem...


Dik

 

[r13]

dik,

The concern is temporary braces during construction of a 3 story high masonry wall. At this stage, it is a cantilever, the slenderness ratio of this wall approaches 200, quite flexible and vulnerable.

 

[dik]

retired13... no doubt about it... bracing is essential... but, correcting the out of plumbness may not be as big an issue...



Dik

 

[r13]

I image the mortar-brick bond is likely to be damaged to an extent, wouldn't it be a concern, and how to correct it, maybe re-patch?