Hydrodynamic Forces Induced in Fluid Containers by Earthquakes

Citation

Conrad, Allan (1956) Hydrodynamic Forces Induced in Fluid Containers by Earthquakes. Engineer's thesis, California Institute of Technology. doi:10.7907/JYF8-KK15. https://resolver.caltech.edu/CaltechETD:etd-03222004-162041

Abstract

This thesis describes an experimental method of measuring the hydrodynamic forces induced in fluid containers when the containers are subjected to varying accelerations. Experiments were performed on a model of a rectangular tank and the forces due to the convective pressures were measured and compared to those predicted by a simplified linear theory in which the fluid system is reduced to a system of simple oscillators. An investigation was made to determine the limit of applicability of this simplified theory and to observe the effect of the non-linearity of the fluid motion on the predicted forces. It was found that the natural frequency of vibration diverged significantly from that for small amplitudes when the amplitude to depth ratio exceeded 0.05. The force-amplitude relation remained essentially constant for amplitude to depth ratios up to 0.20 An electric analog computer was used to compute the dynamic shear forces induced in a typical water tower structure when its base was subjected to the ground accelerations of an actual earthquake. The effect of varying the tower stiffness, on the shear forces induced, was also studied and the results were compared with a modal type of solution. It was found that the modal type of solution gave good results and it is recommended for analyzing earthquake forces on elevated water tanks when an analog computer is not available.

Thesis Files