You note that each anchor tendon is a 6 inch thick steel rod. That is a fairly hefty chunk of steel. Even if the outer 16th inch got corroded, which would be a lot, the rod should still maintain better than 95% of its tensile strength.
Steel in the Golden Gate Bridge, and the Brooklyn Bridge, and many other applications has been in continuous tension for quite a bit longer than the Oroville dam has existed, and that steel is still quite serviceable. Are these anchor tendons so under designed that they commonly fail?
In my experience as a civil engineer, most structures are overdesigned A minimum of 300 to 500%. Maybe with dams, it’s a whole different ballpark though. Considering the consequences, it seems like they’d want to do way better than that.
"You note that each anchor tendon is a 6 inch thick steel rod."
Perhaps there is a misunderstanding of the text... The text of 37' 6" is a length - thirty seven feet six inches long. The diameter of each steel rod is 1 3/8 inches. (Oroville specs). In the Oroville Radial Trunnion Gate anchor tendons, in reference to this picture, anchor tendon (150), encased within a steel sleeve (158), anchor plate (154), nut (156) -(or in other cases a wedge type "grip nut"). Oroville's spillway has 24 anchor tendons to secure the operating loads from each Trunnion Pin (136) (forces from). note: This drawing only shows 1 anchor tendon to each Trunnion Pin. Oroville's construction emplaced grout inside the steel sleeve (158) that encapsulated the anchor tendon (150) after the tendon was tightened to load design tension.
Anchor Tendon example image - for discussion.
Wow, you bring up a good point about structures like the Golden Gate Bridge.
Don’t want to get too far off the Orville Dam topic here, but do you guys have any idea of the assessment of how long the Golden Gate Bridge is built to withstand the continual tension since it was built in the 30’s?