Insight into Strong Motion Behavior of Large Concrete Structures

Abstract

The inability to induce strong motion excitation levels in structures is often cited as a limiting factor in evaluating the seismic performance of large concrete dams. The advent of modern computational tools that provide advanced non-linear analysis capabilities for these structures contributes to the view held by many analysts that low-level response monitoring does not contribute meaningful insights to overall dam performance. Recent experiences with low-level monitoring of two large concrete dams suggest that this may not be entirely true. Results from field tests are discussed in which the ambient testing technique was used to design follow-on forced vibration tests on a large concrete gravity dam and that formed the basis for the evaluation of predicted seismic response behavior of a large multiple concrete arch dam. An overview of the field test procedures employed is described, and sample response measurements are also presented. Details of the time and frequency domain analysis techniques employed are presented and results from each test are interpreted in the context of seismic performance. Recommendations for standardizing field monitoring procedures are provided.