There are distinct stages of "failure" from losing any imbedded Post-Tensioned Anchor Tendon steel rods. The first (1) is loss of strength. This passes the stress to other anchor tendons, which could lead to their failing (an "unzipping effect"). (2) is where a tilt may develop that could bind the trunnion pins. A "binding" could accompany a side force from the Radial Gate slides on the sidewalls of the chute concrete column. (3) if a "tilt" + "binding" occurs, the Radial gate could become inoperable to fully close. Then it would remain open to the scouring depth of 813.6ft of the incoming aggregate covered inlet. (4) Radial Gates are slowly changed in height based on the reservoir "head" (pressure) level to yield a given overall flow rate to the 8 chutes during releases. A stuck gate would cause an imbalance to this choreograph & would imbalance the mixing flows in the immediate upper spillway. (4) any "stuck" open Radial Gate would impede the repair schedules as this is a safety hazard until the gate is blocked off with "stop logs".
An interesting component to the "stresses" that the anchor tendons need to include (but is a smaller factor) are any dynamic forces that ride on top of the hydrostatic forces. Not all is a smooth flow - even though it looks as such. An example is that Hydrodynamic Fluid Flow model testing found that certain gates would feel an "oscillation force" at different frequencies from different flow rates. They measured these "pressure force" oscillations using a large array of tiny piezometer sensors (dynamic strain gauge sensors). Gate 8 had the highest hertz rate or cycles per second near 4 hz. Below are the plots from testings. These dynamic oscillation forces are summed with the average hydrostatic force of the flow & head pressure. (anyone stopped in traffic in the middle of a concrete bridge span will recognize the "flexing" bounce of the suspension waves caused by other moving vehicles - same thing here except on a different scale, but it exists as an oscillating force. The Gate Structure is highly stiff with regard to these waves..the safety factor should well contain any of these boundary summations). But, designers must understand and be aware of resonant frequencies & make sure their designed structure is not aligned/tuned to one of these….
Gate Inlet Pressure Oscillations at different flow rates. Data from piezometer sensors instrumented within the Hydrodynamic Fluid Flow model of the Spillway. Note that certain gates (sensor numbers) & the curvature location in the gate had superimposed water pressure oscillations at various frequencies during flow.
