Full-scale experimental modal analysis of an arch dam: The first experience in Iran |
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| Institution: | 1. Faculty of Civil Engineering, University of Tabriz, Tabriz, East Azerbaijan Province, Iran;2. Faculty of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran;3. Tagliatela College of Engineering, University of New Haven, New Haven, USA;1. Department of Earth and Planetary Sciences, Northwestern University, 2145 Sheridan Rd., Evanston, IL 60208, USA;2. United States Geological Survey, 525 South Wilson Ave., Pasadena, CA 91106, USA;3. Institute for Policy Research, Northwestern University, 2040 Sheridan Rd., Evanston, IL 60208, USA;4. Department of Statistics, Northwestern University, 2006 Sheridan Rd., Evanston, IL 60208, USA |
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| Abstract: | Forced vibration field tests and finite-element studies were conducted on the Shahid Rajaee concrete arch dam in Northern Iran to determine the dynamic properties of the dam–reservoir–foundation system. The first forced vibration tests on the dam were performed with two different types of exciter units, with a limited maximum force, bolted on the dam crest for alternative in-phase and out-of-phase sequencing. Because of an insufficient number of recording sensors, two arrangements of sensors were used to cover sufficient points on the dam crest and one gallery during tests. Two kinds of vibration tests, on–off and frequency sweeping, were carried out on the dam. The primary natural frequencies of the coupled system for both symmetric and anti-symmetric vibration modes were approximated during on–off tests in two types of sequencing of exciters, in phase and out-of-phase, with a maximum frequency of 14 Hz. The principal forced vibration tests were performed at precise resonant frequencies based on the results of the on–off tests in which sweeping around the approximated frequencies at 0.1 Hz increments was performed. Baseline correction and suitable bandpass filtering were applied to the test records and then signal processing was carried out to compute the auto power, cross power and coherence spectra. Nine middle modes of vibration of the coupled system and corresponding damping ratios were estimated. The empirical results are compared against the results from calibrated finite-element modeling of the system using former ambient vibration tests, considering the dam–reservoir–foundation interaction effects. Good agreement is obtained between experimental and numerical results for eight middle modes of the dam–reservoir–foundation system. |
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| Keywords: | Forced vibration test Dam–reservoir–foundation Dynamic properties Finite element method (FEM) Damping ratio Mode shape Shahid Rajaee arch dam |
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