Torsional Radiation Damping of Arbitrarily Shaped Embedded Foundations
Publication: Journal of Geotechnical Engineering
Volume 118, Issue 8
Abstract
Radiation damping of torsionally oscillating, arbitrarily shaped rigid foundations embedded in linear hysteretic homogeneous soil is studied parametrically with a rigorous boundary element formulation. A simplified analytical model, based on sound physical approximations and calibrated against the numerical results, is also developed. The basemat shapes studied include rectangles of aspect ratios up to 6, circles, triangles, and T‐shapes. Particular emphasis is placed on the effects of the depth of embedment and the extent of contact between sidewalls and surrounding soil. It is shown that even foundations placed in an open trench, without sidewall‐soil contact, radiate energy more effectively than surface foundations with an identical basemat. Additional radiation damping is generated from vertical side‐walls, even if they are in good contact with the soil only over a small height compared with the embedment depth; hence, separation or slippage between sidewalls and soil near the ground surface would not substantially affect the amount of torsional damping. Physical arguments are put forward to explain these findings and develop insight to the problem. The paper concludes with an illustrative numerical example.
Get full access to this article
View all available purchase options and get full access to this article.
References
1.
Ahmad, S., and Gazetas, G. (1992). “Torsional stiffness of arbitrarily shaped embedded foundations.” J. Geotech. Engrg., ASCE, 118(8), 1168–1185.
2.
Chen, H., Roesset, J. M., and Tassoulas, J. L. (1984). “Dynamic stiffness of non‐uniformly embedded foundations.” Geotech. Engrg. Report GR84‐10, The Univ. of Texas at Austin, Austin, Texas.
3.
Day, S. M. (1977). “Finite element analysis of seismic scattering problems,” Ph.D. thesis, Univ. of California, La Jolla, Calif.
4.
Dobry, R., and Gazetas, G. (1986). “Dynamic response of arbitrarily shaped foundations.” J. Geotech. Engrg., ASCE, 112(2), 109–135.
5.
Fotopoulou, M., Kosanopoulos, P., Gazetas, G., and Tassoulas, J. (1989). “Rocking damping of arbitrarily shaped embedded foundations,” J. Geotech. Engrg., ASCE, 114(4), 473–490.
6.
Gazetas, G. (1983). “Analysis of machine foundation vibrations: State of the art,” Soil Dyn. Earthquake Engrg., 2(1) 2–43.
7.
Gazetas, G., and Dobry, R. (1984). “Simple radiation damping model for piles and spacing.” J. Engrg. Mech., ASCE, 110(6), 931–956.
8.
Gazetas, G., Dobry, R., and Tassoulas, J. L. (1985). “Vertical response of arbitrarily shaped embedded foundations.” J. Geotech. Engrg., ASCE, 111(6), 750–777.
9.
Gazetas, G., and Tassoulas, J. L. (1987). “Horizontal damping of arbitrarily shaped embedded foundations.” J. Geotech. Engrg., ASCE, 113(5), 458–475.
10.
Kausel, E., and Ushijima, R. (1976). “Vertical and torsional stiffness of cylindrical footings.” Res. Report R76‐6, Massachusetts Inst. of Tech., Cambridge, Mass.
11.
Tassoulas, J. L. (1981). “Elements for numerical analysis of wave motion in layered media.” Res. Report R81‐2, Massachusetts Inst. of Tech., Cambridge, Mass.
12.
Veletsos, A. S., and Nair, V. V. D. (1974). “Torsional vibration of viscoelastic foundation.” J. Geotech. Engrg. Div., ASCE, 100(3), 225–246.
13.
Veletsos, A. S., and Tang, Y. (1987). “Rocking vibration of rigid ring foundation.” J. Geotech. Engrg., ASCE, 113(9), 1019–1034.
14.
Wolf, J. P. (1988). Soil‐structure interaction analysis in time domain. Prentice‐Hall, Inc., Englewood Cliffs, N.J.
15.
Wong, H. L., and Luco, J. E. (1978). “Tables of impedance function and input motions for rectangular foundations.” Report No. CE78‐15, Univ. of Southern California, Los Angeles, Calif.
Information & Authors
Information
Published In
Copyright
Copyright © 1992 ASCE.
History
Published online: Aug 1, 1992
Published in print: Aug 1992
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.