Date of Award
1993
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
Seismic design of concrete gravity dams is usually based on a two-dimensional analysis of one monolith, or slice. This analysis provides the basic information but neglects the interaction between adjacent dam monoliths and assumes uniformity of dam section, foundation properties and ground motions along the dam longitudinal axis. While the seismic response of gravity dams has been investigated in considerable detail, the effects of ground motion spatial incoherence on dam response have not been investigated to any great detail.;In this study, dam response to spatially variable seismic excitations is theoretically investigated. Deterministic and random representations of the space-time random field of the ground motion are included.;Available models for the spatial coherency function are critically reviewed and unified in a general model. This model agrees well with theoretical studies, coherency established for similar random fields, and data collected during recent earthquakes. Two novel simulation techniques for generating spatially multi-dimensional seismic motions are developed. These simulation techniques allow for the digital simulation of ground motions in the near and far fields of small and extended faults. They are computationally efficient and require the summation of cosine functions only.;For long dams, a simplified analytical model, complementary to the conventional two-dimensional analysis is formulated. Dam-reservoir-foundation interaction is accounted for including water viscosity and through-rock interaction of foundation elements. Both continuous and segmented dams are considered. An extensive parametric study is conducted and the relative importance of the main parameters is identified.;Responses of long structures to spatially incoherent ground motions are also derived in closed forms neglecting soil-structure interaction.;The results suggest that both spatial incoherence and wave passage effects can produce significant stresses on dams. The effects of spatial incoherence are qualitatively different and can be more important than those of fully correlated travelling waves. Dam response is considerably affected by the interaction with the foundation and the reservoir.;The formulations presented are quite general and may be equally applicable in response analysis of other structures subjected to similar random fields such as those of turbulent wind and sea waves.
Recommended Citation
Ramadan, Osman Mohamed, "Ground Motion Spatial Incoherence, Its Modelling And Effects On Long Gravity Dams" (1993). Digitized Theses. 2225.
https://ir.lib.uwo.ca/digitizedtheses/2225