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Double T Bleachers

Double T Bleachers

Double T Bleachers

Our firm was invited to bid on a project that involves the repair of deteriorating double T concrete bleachers. I am trying to get some opinions or ideas as how to go about doing this.  One idea is to use Fiber Reinforced Polymers and epoxy injection and I would like to know if this is the best way to go about it.  Any help would be greatly appreciated.   

RE: Double T Bleachers

Depending on the deterioration type and severity, you could consider carbon fiber overlay, epoxy injection or a combination of these.  Assuming these are precast,pre-stressed sections, check the damage to the strands.  Neither carbon fiber overlays, nor epoxy injection will restore losses in pre-stressing capability.  

RE: Double T Bleachers

I would also check on the DT load capacity - with loss of reinforcing area with oxidation you might have an issue.  Prestressing tendons are especially prone to rusting as they are a more refined steel.

If you don't havd information about the reinforcement and tendons inside the DT's a load test might be in order.

I posted this earlier last year:

I did a load test once on a small grandstand - made of load bearing CMU with double tees forming each riser.  No one had a clue where the DT's came from and what load capacity they truly had.

I had a number of barrels set up in a specified spacing to load the grandstand to 125% of the required live loading for grandstands (100 psf I think it was).  The loading was performed by adding water to the barrels - calculating the volume in each barrel, the resulting weight, and the barrel spacing to mimic 100 psf.

I took vertical elevation measurements of the DT's prior to loading, at 1/4 loading, 1/2, 3/4 and full loading.  Then removed the load, took measurements, and then took them again I think at 24 hours later.  (I don't have ACI with me right now but this is what I recall).

ACI provided design criteria for the deflection and deflection-rebound.

RE: Double T Bleachers

Replacement double Tees could be the most cost effective solution.  Get some bids from precasters and compare to repair costs.

RE: Double T Bleachers

First things first. Do you know why the DT's have deteriorated? If so, then you can select the proper method of repair.

If a study has not been done to determine first the cause, then a would suggest a 2 part project:
1) to determine the cause
2) to design the repair

RE: Double T Bleachers

I was actually getting my initial information from an RFP, but we finally attended the pre-bid meeting and had a chance to visually inspect the double T's.  Luckily, the double T's themselves are intact, however, they have shifted around considerably and their connections to the supports are coming apart.  The connections are embedded plates welded together and the welds are shearing off.  The shifting may be caused by setteling foundations which is something we would have to investigate should we get the job.  

Thank you all for your replies, they are greatly appreciated.

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