You cited a year 2000 DWR report that said two of the Oroville anchor tendons had broken. Did they replace those tendons? How do you get a broken tendon out of 37 feet of concrete?
“... How do you get a broken tendon out of 37 feet of concrete? “
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I have been wondering the same thing.
And... just what exactly are these “tendons”?
Are they just a big steel rod that is threaded on each end
and tightened down to a certain torque specification?
An earlier post mentioned they were inside of a sleeve.
The dumb answer is: you get them out the reverse way you put them in,
but if you try to get it out and it breaks half way down, then what?
The 2 failed Oroville spillway tendons have been replaced. However I have not been able to find bid instructions for these two tendon repairs. I have found DWR bid repair instruction documents for the replacement of tendons in the Clifton Court Forebay Dam. See below.
There are significant construction differences between Oroville and Clifton Court Forebay Dam tendons. Oroville's anchor tendons are encased within a steel sleeve, with grout emplaced between. Whereas Clifton Court's tendons are not encased within a sleeve. Oroville's tendons are tightly spaced with an array of two rows of 12 (total 24) tendons per trunnion side in a tight grouping. Clifton's tendons are just two larger tendons per trunnion side (easier access). Oroville's tendons are post-stressed while Clifton's are pre-stressed.
Replacing the Clifton tendons are easier (see below) verses Oroville's. We had upthread discussion on how Oroville tendons likely would be done. The challenges would be in (1) coring either inside of the sleeve to drill out the tendon & grout. or (2) coring out the whole sleeve & tendon (larger diameter core hole). If (2), then there is the necessity emplacing of two layers of re-grouting of outside the new sleeve and inside the sleeve. If you have 2 layers, you have 2 curing times as the sleeve will act as a binding seal on the post-tensioned anchor. The other challenge is the "Tee" anchor (7 inches by 2 inches approx). It likely needs to be removed from the side of the Chute Column as a "coring" diameter that encompasses a "Tee" may be too large for the tightly spaced grouped array of tendons. If the tendon to be replaced is in an inner "Tee" location, then the neighboring Tee anchor will likely be in the way from the side access. This too must be fixed & replaced (possibly another whole tendon assembly) if "cut through" to get to the inner tendon anchor.
Reversing the process: The new tendon "Tee" anchor must be grouted in first - then wait for curing to load strength - then the tendon is tensioned to the specified tensile load (near 160,000 psi), (somewhere in the process grout is emplaced in the sleeve - the grout will then cure to strength).
= = Clifton Court Forebay Dam Bid on replacing anchor tendons:
2. Install new anchor tendons for Radial Gates 1, 3, and 5 on the Clifton Court Forebay control structure. This work includes the following principal features:
a. Modify existing concrete control structure piers and abutments.
b. Core new holes, install, grout and tension new anchor tendons.
c. Fabricate and install new bearing plates.
DWR bid instructions on Tendon Replacement - Clifton Court Forebay Dam