Help me identify this water tank failure? 1

[clarke1973]

Can anyone offer any ideas as to how this failure has occurred in a water tank in the attached photos?
The tank construction consists of a GRP wall, with steel framing around the outside, presumably to provide lateral restraint to the tank. The framing sits on RC beams which are on a raft footing.
One of the steel columns has completely sheared through the RC beam and pulled away from the tank, bending the horizontal ring beam in the process. It is clear that the baseplate anchors where installed outside the beam reinforcement, significantly reducing the shear capacity.
On first appearance it looks like the horizontal pressure from the tanks has caused the failure, however the tank wall itself is still intact with no apparent evidence of stress in the seem connection. The client is certain that vehicle impact has not occurred, however I have my doubts. There is no evidence of impact on the steel column however.
does anyone have any thoughts?
Thanks in advance

 

[LittleInch]

Are you sure the ring beam hasn't buckled or been subject to some sort of axial force buckling it and finding the weak spot as the connection from the column. How long / what is the end connection of the buckled beam.

Has that been hit?

Can't see how the tank can affect that support.

A few more pictures would help.

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[clarke1973]

Thanks for the reply littleinch.
That is a possibility. I don't know what the beam end connection is though unfortunately. I've attached more photos

 

[clarke1973]

another photo

 

[SAIL3]

just one col failure.....which one?....why just this one particular col?...how is this col different than the others in construction and loading?...these are some of the questions that would come immediately to mind....one immediate cause may be the lateral pressure on the col and it"s resulting shear @ the base but then the question arises why no sign of distress @ the other cols?...

 

[IRstuff]

I would bet that the concrete got hit somehow. The level of rust on the bolts suggests that it's been like that for a long time. This is further indicated by the lack of debris from the footing.

Seems more likely that the footing failed or was hit, and the column, without its foot, pulled the ring out.

TTFN (ta ta for now)
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[BAretired]

A wedge shaped chunk of concrete below and left of the column has a different color and texture from the rest of the beam. It appears to have been poured afterwards for some unknown reason. The concrete which has been removed appears to have failed in a vertical line following a vertical bar which is visible in the photo.

It looks like a tensile failure caused by water pressure, although impact is a possibility too. It was not adequately tied to the beam to resist any significant horizontal force.

BA

 

[bridgebuster]

A drawing of the tank would help. Is the I beam supposed to be connected to the tank wall? Your first photo shows two open vertical holes? As BA pointed out the concrete beam appears to have been two pours, which suggests a repair subsequent to the original construction. The anchor rods look fairly short as well; the rebar doesn't look properly detailed. I'm leaning towards BA's opinion that it's a tensile failure. Is this a pre-engineered tank? If so, call the manufacturer, although they might say they're not responsible for designing and detailing the concrete beams.

 

[oldestguy]

Have you looked at temperature caused expansion of the horizontal steel member, as from sun heating? Could that have moved out the column taking with it the horizontal member?

 

[XR250]

Have you looked at temperature caused expansion of the horizontal steel member, as from sun heating? Could that have moved out the column taking with it the horizontal member?

You beat me to it on that one!

 

[dik]

Are the anchors connecting the steel to the beam expansion type anchors? Is there sufficient width to the beam for the expansion anchors to work?

Dik

 

[TehMightyEngineer]

Interesting mystery, I gotta say that aside from thermal effects I don't see a conclusive explanation for this damage if you assume a vehicle impact is not the cause. Very curious if you do find any more clues.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com

 

[SlideRuleEra]

I assume a GRP tank is pretty flexible. Say that the tank is empty, wind loading causes the tank wall to flex (deflect). Reaction to the wall deflection is that the weakest column base fails in shear (pops outward). BAretired may have spotted why one particular column was susceptible to failure.

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[SteelPE]

Are those anchors post installed wedge anchors?

 

[KootK]

Many of the concrete anchorage failures that I've encountered have been the result of thermal forces. Any cause to suspect thermal expansion here?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[hokie66]

I don't know why it wanted to move that way, maybe expansion of the steel. But there was very little holding it, and this is not the first time it has happened. As pointed out above, the concrete where the anchors were was a sloppy repair. The structural steel appears to be galvanized, but the anchors are not. They look to be expansion anchors, Trubolts or the like, and not corrosion resistant. The corrosion of the anchors could have contributed to the spalling. And there was no reinforcement which was effective in restraining the anchors.

All in all, destined to fail.

 

[hokie66]

Is that column connected to the tank higher up? If so, how did those connections fare?

 

[LittleInch]

The larger view seems to show that the columns are fixed across the top of the tank to create a ring around the tank.

The column that failed seems to be on the outside.

It is feasible that the tank did expand when filled as the column seems to be in close contact with a vertical seam. Given that examination of the first photo seems to show a repair line then this column and foundation appear to be more prone than the others to failure of the concrete and column being pushed out than the others

I don't really understand why those columns are there, but maybe to support a platform on top of the tank? If so why place it so close to the tank.

If you look at the tank to the left, it seems to be a similar size, but has a much meatier connection of the columns to a slab, not a set of supports.

Was the tank actually installed 90 degrees wrong? i.e. those columns should sit on the much bigger beams on the left and right?? or were the beams cast 90 degrees out?? Stranger things have happened and then everyone just goes - Sod it put it on the bases, no one will know and nothing will happen???

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[hokie66]

LittleInch,
I don't understand the system either, but it looks like these "columns" are on all four sides.

 

[LittleInch]

You look as though you're right - Damn - I thought I had a good reason there for a few minutes...

I think BA retired has it best - these columns appear to be an afterthought and were poured after the main supports

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.