In this chapter, dynamic field measurements of three full-scale operational Tainter gates are documented. Measurements of the in-air gate structural dynamics were made when feasible or were simulated using FEM analysis when physical measurement was not possible. In-water structural dynamics were documented using experimental modal analysis with gate excitation supplied by the sudden tension failure of a carefully machined steel rod. The field measurements permitted assessments of the stability of each gate and these assessments are compared with theoretical predictions. Two gates were found to be stable and one was determined to have a potential instability. Theoretical predictions are shown to agree with the experimental results from field measurements.
TopTainter Gate “A”
Field vibration tests were undertaken on a 29-ton Tainter gate, hereafter called Tainter gate “A” (see Anami et al., 2004a). A photograph of Tainter gate “A,” taken from the downstream side, is shown in Figure 1. The configuration and major dimensions are shown in Figure 2. In Figure 2a, the skinplate height is specified as 8.3 m and the skinplate radius is 8.5 m. The span of the skinplate is 8.75 m, as shown in Figure 2b. The skinplate is supported by two truss-structure radial arms. The gate is portal-shaped with the radial arms parallel to the streamwise direction. As shown in Figure 1, many reinforcing bracings are attached on the back side of the skinplate, and many additional bracings are attached between the horizontal girders. The gate elements are riveted together. The entire skinplate structure including the bracing and the horizontal girders has a mass of 21,091 kg and the radial arms have a mass of 7,941 kg. The skinplate mass is about 73% of the whole gate mass of 29,032 kg (about 29 tons).
Figure 1. View of downstream side of Tainter gate “A”
Figure 2. Two views of the 29-ton Tainter gate “A” in Japan showing (a) side view, and (b) the A-A cross-sectional top view
Figure 3. Measurement locations for in-air modal analysis tests on Tainter gate “A” (a) upstream view of skinplate, and (b) side view
In order to determine the in-air natural vibration characteristics, stop logs were installed on the upstream side of the gate to isolate the gate from the water, and experimental modal analysis was carried out.
The gate was raised so it was no longer in contact with the sill. The gate was struck with the instrumented impact hammer in the central portion of the lower horizontal girder in the tangential direction (vertical direction) and the radial direction (streamwise direction) of the skinplate, as shown by the arrows in Figure 2. The acceleration responses of the gate to the impact force were measured at 48 points on the gate (6 points on each arm and 36 points on the skinplate), as shown by the filled circles in Figures 3a and 3b. Two significant directions of vibration were measured at each measurement location. The gate acceleration responses to the impact force were measured with servo-type accelerometers (LS-20C by RION Co.).