The Earthquake Engineering Online Archive

A laboratory study of submerged multi-body systems in earthquakes

Ansari, Gholam Reza

UCB/EERC-83/08, Earthquake Engineering Research Center, University of California, Berkeley, 1983-06, 357 pages (540/A58/1983)

In this theoretical and laboratory study, multi-body and fluid interactions are subjected to a set of boundary conditions, constraints, and excitations. The scales of motion, along with various parameters found in the ocean environment, are investigated and the behavior of ocean-based systems subjected to earthquake excitations is discussed. A multi-variable feedback control system is developed to model the behavior of multi-body fluid interactions. A successive superposition technique is presented using efficiency functions. Key steps in the study were (1) development of physical modeling criteria; (2) generation of time-scaled excitations and their application to the models using an earthquake simulator; (3) variation of geometric configurations and inertia-related properties and the measurement of various response parameters; (4) recording of the three-dimensional motions of the subsystems, surface effects, and pressure distribution on the structures; and (5) development of a dynamic system identification method to measure the addedmass properties of the multi-structure system without constraining any of the degrees-of-freedom. The paper includes an explanation of the applications of various signal processing techniques to the experimental study of fluid-structure systems. The importance of transient analysis is discussed and the coupling of transverse and in-line degrees-of-freedom is measured. It is shown that the systems with well-spaced modes can behave similarly to closely spaced mode systems when placed in a fluid.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-83-08.pdf (18 MB)