The Earthquake Engineering Online Archive

The behavior of submerged, multiple bodies in earthquakes

Liao, Wen-Gen

UCB/EERC-82/16, Earthquake Engineering Research Center, University of California, Berkeley, 1982-09-01, 138 pages (540/L528/1982)

In order to investigate the nature of hydrodynamic interaction between two (or more) cylinders subjected to earthquake ground motion, a numerical analysis is presented for determining the hydrodynamic forces acting upon a nonaxisymmetric offshore structure and the corresponding structural responses. With the assumption of potential flow theory, a finite element method is developed to solve the boundary value problem in the fluid domain, which, because of symmetry, is reduced to one half. A localized finite element method utilizing eigenfunction expansions is also outlined in detail. If the cylinders have uniform cross sections, the three-dimensional problem can be reduced to a two-dimensional one and the computation becomes much more efficient. A computer program is developed to analyze the hydrodynamic forces and the structural responses according to the above-mentioned analysis procedure, and illustrative examples are presented. Compared with the experiment results for a physical model on an earthquake simulator, the results are generally in agreement. The results established indicate that hydrodynamic interaction is relevant if the cylinders are close, and that this phenomenon depends on the characteristics of the structure, water depth, excitation frequency, amplitude of ground motion, and direction of excitation.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-82-16.pdf (7 MB)