Precast Wall Panel - Crack at Connection

[Structures33]

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

 

[Ron]

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

 

[hokie66]

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

 

[msquared48]

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

 

[hokie66]

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?

 

[sonofamsquared48]

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.

 

[hokie66]

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.

 

[msquared48]

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

 

[msquared48]

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

He is also a CE in Washington.

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

 

[sonofamsquared48]

Hay there pops. Just infiltrating your circle.

 

[hokie66]

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.

 

[msquared48]

Yea... Like that's never happened!

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

 

[sonofamsquared48]

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

 

[rowingengineer]

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

 

[rowingengineer]

steal=seal

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

 

[civeng80]

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.

 

[Ron]

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.

 

[civeng80]

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.

 

[slickdeals]

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

 

[Structures33]

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.