Measuring Trunnion Friction on Tainter Gates

BDI was subcontracted to temporarily install instrumentation on three dam Tainter gatesĀ  to determine in-place trunnion friction coefficients. BDI used their SPRAT Level I qualified ropes access personnel to install a total of 65 sensors on each gate consisting of strain, rotation, displacement, and torque instrumentation. SPRAT Level III oversight was subcontracted through Rhino Access. Once the gates were instrumented, periodic monitoring of the instrumentation during spilling tests was performed and subsequently stored in BDI datalogging equipment. Each gate was instrumented and tested in one day for a total field duration of three days.

Following the field work phase, BDI’s Registered Professional Engineers conducted analysis by converting strain measurements into axial forces and bending moments at each member cross-section. In turn, the measured forces were applied to pin-strut free-body diagrams so that the moment resistance could be computed for each of the six pins. The resulting trunnion friction coefficients were found to be consistent and well below the FERC-mandated design value.