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Precast Wall Panel - Crack at Connection

Precast Wall Panel - Crack at Connection

Precast Wall Panel - Crack at Connection

(OP)
What is typically done to repair a cracked connection area (at the welded conn plate) on a precast wall panel? See attached photo please.  

RE: Precast Wall Panel - Crack at Connection

That's minor.  Clean it up, remove the spall, and use repair mortar  or sealant repair.

RE: Precast Wall Panel - Crack at Connection

That is a good example of why precast panels shouldn't be welded together.  Both panels are cracked.

RE: Precast Wall Panel - Crack at Connection

Hokie:

With the properly detailed, and implemented, welded connection between panels, this would not have happened.  There are connections out there that do allow lateral expansion/contraction.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Precast Wall Panel - Crack at Connection

I suppose if you move the welding far enough away from the joint and reinforce the panel accordingly, you could control cracking a lot better than in the photo shown.  But why would you want to tie the panels together anyway?

RE: Precast Wall Panel - Crack at Connection

A few things can cause cracking of this nature around connections.  The first is shrinkage of the concrete panel due to high water content in the concrete mix design.  The second is where a connection utilizes thin steel plates and a lot of welding.  The steel plate heats up, expands and causes the crack in the concrete.  The third, which is less prevalent, is thermal expansion due to ambient temperature changes.  The fourth possibility involves improper handling of the panel when the crane is setting the panel into place.  I typically resolve cracks with epoxy injection to make sure that there is a seal from the elements to protect the underlying reinforcing or plating materials.  Panels are typically attached along the vertical faces at the roof to develop a chord for the roof diaphragm.  Panels are often connected at the mid-height of the wall (or whatever cadence is desired) to align the panels together.  When the panels are lifted from the casting slab they can often deform slightly and from more of an aesthetics basis are really forced into a uniform profile, hopefully vertical.

RE: Precast Wall Panel - Crack at Connection

Welcome, son of Mike.  I understand the reasons for connecting the panels together by welding, but still would not do it.  What is shown in the photo happens all too often for my liking.

RE: Precast Wall Panel - Crack at Connection

If you look closely at the connection, it is made of multiple rebar welded together to completely fill the gap and then welded to both panels.  There is no room for any movement whatsoever.  That's the mistake.

The way to do it, if it needs to be done, and I do see your point here Hokie, is to limit the gap to 5/8" to 3/4", and fill the gap with a single #4 bar 6" long, welding the bar 2" on one side at one end, and 2" on the other side at the other end.  That way there is space for expansion and contraction.  I have also seen the same thing done with bent angles, but I have also seen more cracking with that one due to the increased rigidity of the angle.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Precast Wall Panel - Crack at Connection

That went over the top.  I finally got it after he called me.  Man it's been a long day.  Damn kid!  bigsmile

He is also a CE in Washington.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Precast Wall Panel - Crack at Connection

Hay there pops.  Just infiltrating your circle.

RE: Precast Wall Panel - Crack at Connection

Mike,
And here I was thinking you had deputized your son to fight your battles.  What I am waiting for now is for the two of you to get on opposite sides of an argument.

RE: Precast Wall Panel - Crack at Connection

Yea...  Like that's never happened!

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Precast Wall Panel - Crack at Connection

Let's role play.  I am Luke Skywalker and you are the heavy breathing, out of shape, evil darthvader.

RE: Precast Wall Panel - Crack at Connection

I wonder how the water proofing is surviving at this connection? The inside steal is compromised by the looks of things.

I agree with hokie, no compelling reason to weld the panels at mid height or at all. My rule of thumb is only one welded connection per panel. I wonder how this detail works at corners?
 

An expert is a man who has made all the mistakes which can be made in a very narrow field

RE: Precast Wall Panel - Crack at Connection

steal=seal

An expert is a man who has made all the mistakes which can be made in a very narrow field

RE: Precast Wall Panel - Crack at Connection

I agree that its not a good idea to have such a connection for concrete panels.

I would tend to think that the crack would be more due to the heat from site welding expanding the rebar and cracking the concrete than any movement or shrinkage since the panels look quite new.

However its likely the crack will worsen due to movement.

RE: Precast Wall Panel - Crack at Connection

civeng80...no, it is the panel movement that typically causes this stuff.  Think of it as a dog (the panel) wagging its tail (the connection).  As long as the tail is loose, the dog's happy.  If you grab the tail and try to hold it down, the dog isn't happy and will try to pull the tail away.

RE: Precast Wall Panel - Crack at Connection

It looks to me that this panel has only very recently been put up.  Weld has still not been primed. Joint has not been caulked up.

The dogs tail hasn't had time to wag yet !

Movement for a crack like that would take some reasonable time to happen.

RE: Precast Wall Panel - Crack at Connection

You could have easily been sonOFmsquare48, but you chose to be son OF A ???

RE: Precast Wall Panel - Crack at Connection

(OP)
The panels were installed about 2.5 weeks before the photo was taken.  I'm attaching another photo that shows a better view of the connection.  This is not how the connections are specified on the plans - the connections were supposed to be plates welded to plates embedded in the panels. There are 5 connection points along the height of the wall. I am doing periodic construction inspections but did not do the original design so it's possible that the drawings were revised and we did not receive the updates.  
I have another question but will post separately with another photo.  

RE: Precast Wall Panel - Crack at Connection

This crack almost looks like the concrete overlapped the embed plate a little, and when the panels moved a little it spalled the corner off.  Still nothing to worry about

RE: Precast Wall Panel - Crack at Connection

slickdeals - well, I know that the handle has some evil overtones although, being his progeny, I have recieved a heavy dose in the genes.  I know that he will counter.  All in good fun.

I believe as well that the connection is not really much of a structural concern.  But still needs to be fixed.  When I look at the root of the weld nearest the spaul, it looks rather healthy.  I am siding with expansion of the plate due to the welder not allowing the weld to cool as well as maby the base plate not being thick enough to provide for a proper heat sink.

Cheers all
 

RE: Precast Wall Panel - Crack at Connection

The two photos are of two different connections.  If you look closely at the first photo, there is a crack on the right side some distance from the joint.  To me, that discounts the theory that this is only localized due to welding heat.  The cracking is due to restraint of volume change due to shrinkage and/or ambient temperature variation.

I would cut loose all these connections before bothering to do any repairs, as otherwise the problem will just repeat.  If this were my new building, I would not accept that it is "nothing to worry about".

RE: Precast Wall Panel - Crack at Connection

I agree with Hokie66.  The right crack in the first photo would be due to movement and shrinkage and is more incidious and serious, this one will grow. If this was my building I would be concerned.  The connection is not a good connection.

Just for the record, I would join the panels with a fish plate bolted to ferrule bolts with slotted holes  (recessed if concealment is required).

As a matter of interest what would you guys do to join the panels?

RE: Precast Wall Panel - Crack at Connection

In the secondphoto, the gap appears excessive in width - I would guess 1.5 to 2".  Must be a longer pair of panels.

The connection is rigid too - cannot expand or contract.  No wonder the failure.

I have already described the connection I would have used.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Precast Wall Panel - Crack at Connection

If this was my project, I wouldn't be welding the 2 panels together.

RE: Precast Wall Panel - Crack at Connection

Ron and Civeng80:

The movement need not be just due to temperature, it could also come from the normal shrinkage of the curing process.  Can be quite a bit in panels of that size.  I expect something on the order of 1/4" over the width of each panel.

OP:  

How old were the panels when they were picked?  

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Precast Wall Panel - Crack at Connection

OP:

Additionally, how old were the panels when the welds were made?

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Precast Wall Panel - Crack at Connection

(OP)
I would say the panels were between 3 and 4 weeks when they were placed.  It was another week before they started the welding on the ones that were shown in the pictures.

RE: Precast Wall Panel - Crack at Connection

Doesn't matter.  Drying shrinkage continues for a long time, and ambient temperature variation is always there.

RE: Precast Wall Panel - Crack at Connection

I think with concrete panels (and masonry also) its best to allow for as much flexibility in joints as possible.  So its probably better not to tie the panels up at all. There will always be movements from temperature, shrinkage, foundation movements, creep and maybe more.

Without knowing the complete structural arrangement, however, I cannot comment this.

RE: Precast Wall Panel - Crack at Connection

mssquare48

Couldn't agree more with your comment on movements of large panels.

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