Vibration Studies of Monticello Dam. A Water Resources Technical Publication

摘要

Tests conducted on Monticello Dam demonstrated the feasibility of determining dynamic properties of a concrete arch dam by measurement of the accelerations of the structure when excited by vibration generators. This research report includes a brief description of the vibration equipment and test procedures used and a discussion of some of the measured results. During the 10-day test period, acceleration measurements using unbonded resistance wire accelerometers were made on the crest and downstream face of the dam to obtain natural frequencies for the first five modes of vibration and the deflected shapes of the crest and of three cantilevers for the first four modes. Two test series were performed, before and after the mode shape tests, to obtain resonant frequencies of the dam. Frequency response data were obtained by measuring accelerations for small increments of shaker speed over the range of 2 to 8 cycles per second. Damping ratios for small displacements were determined from the frequency response curves. Vibration generators used were of the counter-rotating eccentric-weight type, with all components light enough to be manhandled on the dam. With this equipment, sinusoidally varying forces can be applied along any predetermined axis.