Dynamic Response of Arbitrarily Shaped Foundations: Experimental Verification
Publication: Journal of Geotechnical Engineering
Volume 112, Issue 2
Abstract
Results of twenty‐one free vibration tests on surface model footings on moist sand having different base shapes and about equal base area have been reported by Stokoe and Erden (5,8). These tests are used here to verify the analytical method of the companion paper (3), for circular, square and rectangular base shapes with aspect ratios up to 6, and including vertical, torsional and coupled swaying‐rocking oscillations. Close agreement is found between predicted and measured frequencies in all cases, and also between damping ratios in vertical and torsional vibration. The experiments provide strong support for the vertical and torsional radiation damping graphs developed in Ref. 3, including verification of the increased damping ratios predicted for the longest footings. The accord is also reasonably good for damping in those swayingrocking tests in which rocking and material damping are dominant and the overall damping ratio is about 3%. However, the method of Ref. 3 overpredicts the measured swaying‐rocking damping ratios in those tests in which swaying and radiation damping are also important, and for which larger damping ratios are predicted (4% to 9%). This discrepancy between half‐space predicted swaying‐rocking damping and measured values is explained by the effect of boundary wave reflections on the test results.
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References
1.
Dobry, R., “Soil Properties and the One‐Dimensional Theory of Earthquake Amplification,” thesis presented to the Massachusetts Institute of Technology, at Cambridge, MA, in 1971, in partial fulfillment of the requirements for the degree of Doctor of Science.
2.
Dobry, R., Gazetas, G., and Stokoe, K. H., II, “Dynamic Response of Arbitrarily Shaped Foundations: Experimental Verification,” Research Report, Dept. of Civ. Engrg., Rensselaer Polytechnic Institute, Troy, NY, 1985.
3.
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4.
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5.
Erden, S. M., “Influence of Shape and Embedment on Dynamic Foundation Response,” thesis presented to the Univ. of Massachusetts at Amherst, in 1974, in partial fulfillment of the requirements for the degree of Doctor of Philosophy.
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Richart, F. E., Hall, J. R., and Woods, R. D., Vibrations of Soils and Foundations, Prentice‐Hall, 1970.
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Roesset, J. M., Whitman, R. V., and Dobry, R., “Modal Analysis for Structures with Foundation Interaction,” Journal of the Structural Division, ASCE, 99(3), Mar., 1973, pp. 399–416.
8.
Stokoe, K. H., II, and Erden, S. M. “Influence of Base Shape on Dynamic Response of Surface Foundations,” Geotechnical Engineering Report GP85‐1, Civ. Engrg. Dept., The Univ. of Texas at Austin.
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Woods, R. D., “Screening of Elastic Surface Wave by Trenches,” thesis presented to the Univ. of Michigan, at Ann Arbor, in 1967, in partial fulfillment of the requirements for the degree of Doctor of Philosophy.
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Copyright © 1986 ASCE.
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Published online: Feb 1, 1986
Published in print: Feb 1986
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