Precast Panel Wall Deflection

[bpstruct]

I looked at a building last week that has precast concrete panels for the building skin. They are not load bearing and are only nominally connected to the building at the roof line. The panels just sit on the footing - no connection. They were apparently used as a blast barrier of sorts and designed to collapse under blast pressures leaving the building standing. There are isolated panels 4 or 5 total around the building that appear to be deflecting - no pattern. One is out about 3.5" at midheight. No signs of distress or misalignment (in either direction) at the footing or roof line. There are no foundation issues. The perimeter grade beam sits on void boxes on large piers. I cannot make sense of the deflection. The current owner does not know when this started. They may have been like that when he bought the property. Wondering if these panels could be curled and have simply always been like this. The panels are 8" thick and roof is at 27.5 feet. Any thoughts?

 

[ztengguy]

Any way to know if they were pre-stressed or post tensioned?

 

[bpstruct]

Not for sure. There are no panel details.

 

[concretemasonry]

They sound like a typical prestressed panel without insulation (insulated are 12" thick or so). They are made on long(400' or so) beds and cut to length. The camber can vary, depending on the location of the panel section in the production run.

If you know the date of the building construction, you might look to a local precast panel supplier (not too many within a 100 miles marketing area) and find out what may have been supplied (most plants are PCI members and have detailed information of all production). If you talk to an engineer, you may get some detailed information of the product characteristics, performance and other items. They are usually lightly connected to the structural system at the top to resist the wind loads, but not to resist any large interior pressures.

the engineers at some precast plants are willing to give general information on their products.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[asixth]

I've heard of this happening before with tall skinny panels so I always check that the minimum height to thickness ratio is used. From memory I think it is 50 so you are still within this max but the panels would look skinny. If there is different reinforcement provided in each face that can cause the panels to curl with the different restraint to shrinkage.

 

[rowingengineer]

What was the temperature inside the building compared to outside? Wouldn't happen to be a cold room or sorts?

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