For those that have been wondering, the prior images of the Radial Trunnion Anchors show areas where there is a solid connection between certain gates - via a Trunnion Beam. Only gates 1, 4, 5, and 8 have these.
The "box beams" (see image below) are designed to handle a specific problem discovered in the concrete stiffness of the Headworks. Analysis found that the stiffer sides of the radial gate mounting would have a different "differential" movement during a seismic event than would the thinner standard vertical gate concrete columns. Thus the larger volume & stiffer concrete is located at the ends of the monolith Gate Structure (outside gate 1, outside gate 8) and in the middle (double thickness column between gates 4 & 5).
This forms the greatest differential in concrete column density on Gates 1, 4, 5, & 8. The differential movement could cause damaging stress to the Anchor Tendons via the Massive Steel Radial Trunnion Gate - via the pins to the anchorage. To "fix" this, they added massive connecting box structures between the Trunnion Anchorage (near the pins) on these gates. Side note: Either the Division of Safety of Dams Inspector was unaware of the root "seismic" necessity, or the Inspector believed or was told these beams were simply for anchorage balance.
In any case, this notation created an oddity in the 2015 inspection report as images clearly revealed that these were not on every gate. Thus, a reader may believe that there were "missing" balancing force beams, or there was some other underlying reason. That is what led me to research the real history on these beams. I suspected a torsion force on the structure - which it was: via a seismic event (via analysis). So why didn't the Inspector include the notation of "seismic"?
View of Thick Box Beam Structure Connecting both sides of the Trunnion Pivot Anchoring. This Modification was done in 4 Gates where the differential stress from an earthquake could damage Anchor Tendons. Note: Inspectors notes for pic are misleading (do not mention Seismic or Quake analysis origin).
