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

 

[clarke1973]

Thanks for all the replies. Some interesting theories there.

Hokie66 - at the top of the columns there is a series of horizontal ties connecting the columns together. all the other connections are fine, it is just that one column at the base that has failed.
I doubt that thermal expansion is a factor as there are a number of water tanks there in the vicinity (exact same construction) and only this one has the problem.a few of them do have some cracks at the end of the RC beams though indicating that the problem with the anchors is consistent.
I'm still at a loss though as to why the column would push out that far and how the horizontal beam has deformed the way it has.

 

[prex]

Those 'columns' are not really columns, but vertical beams: they resist water pressure, the GRP walls with metal corners cannot of course withstand the pressure as flat plates in bending. So I guess that simply one of the beams simply failed at the base (due to inadequate design and manufacture, possibly aided by an impact). There must have been a pretty large deflection of the wall, but this could have been elastic, so it is no more visible.
One condition for this to be true is that the tank was not empty at the time of the failure, and that, when clarke1973 visited the tank, it had been already emptied.
Now of course many questions will arise, for clarke1973, on the acceptability of the other beam supports and perhaps other bad details of this and other similar tanks.


prex
[URL unfurl="true"]http://www.xcalcs.com[/url] : Online engineering calculations
[URL unfurl="true"]http://www.megamag.it[/url] : Magnetic brakes and launchers for fun rides
[URL unfurl="true"]http://www.levitans.com[/url] : Air bearing pads

 

[SlideRuleEra]

I agree with prex. The tank has more in common with a cofferdam than a "tank". The bottom of the tank keeps the tank wall from failing, but does not prevent the center of the wall from bulging:

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[LittleInch]

If you look at pictures of others then it seems this is the case.

The only thing to maybe check is to see if that horizontal beam which is deflected was actually or was supposed to be bolted to a beam running under the tank. Connection details on other tanks seem to show you build the beams like a complete box.

If you look closely there seems to be room for four bolts holding the beam/column to the base, but only two have been used.

you can just see in the first photo there is a horizontal beam under the tanks along the line of the concrete beam, but not clear how / if it was attached to the bent channel.

Lots to investigate!



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

 

[RHTPE]

It appears to me that the concrete beam that the column was attached to had been repaired in some fashion, judging by the difference in color each side of the diagonal crack visible in the first picture. I see no evidence of reinforcing steel emerging from the intact concrete. Perhaps a patch/repair was done after the original concrete was placed and was not properly tied to the original concrete and quite possibly was done with lesser quality concrete.


Ralph
Structures Consulting
Northeast USA

 

[oldestguy]

Now this one should be labeled a "typical Rube Goldbereg tank design." What a bunch of beams and columns with no apparent experts doing the "design". Going in and replacing or "repairing" those concrete "beams" will surely be a job. Looking back, perhaps a series of many more photos would have shown the problem right away. Good luck fixing this mess. Full replacement may be cheaper.

 

[azcats]

Those 'inward' sets of wedge anchors appear to be bent as well. I'm on board with SRE's latest sketch.

I wouldn't trust any of the anchorage at the bottom anymore. Seems an 'easy' fix might be take shear out of the anchors by adding tension struts or rods across the bottom to opposing vertical beams just like they did at the top. Doesn't seem like it'd be that hard to retrofit.

 

[lilliput1]

There should be X bracing on each of the 4 sides to resist lateral force and prevent bending of any column. If a column bends out of alignment is center of gravity will act to create a moment at the base causing the concrete base to spall and the bottom of the column pulled out the bottom beam of the tank.

 

[Sawbux]

Maybe someone put a sling around the column and yarded some equipment around?

Looks to me like the horizontal beam was originally under the lip of the tank.