- Author
- Marshall, R. D. | Phan, L. T. | Celebi, M.
- Title
- Measurement of Structural Response Characteristics of Full-Scale Buildings: Comparison of Results From Strong-Motion and Ambient Vibration Records.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD Geological Survey, Menlo Park, CA
- Report
- NISTIR 4884, October 1992, 85 p.
- Distribution
- Available from National Technical Information Service
- Keywords
- buildings | damping | earthquakes | instrumentation | dynamic response | field measurements | signal processing | structural dynamics | structural systems
- Abstract
- This report describes the collection and analysis of ambient vibration data from five buildings in the San Francisco Bay area that experienced strong shaking during the Loma Prieta earthquake of October 17, 1989. The buildings represent a range of construction materials, structural systems, foundation systems and building dimensions. Results of the analyses are compared with similar analyses carried out on strong-motion response records obtained from the same buildings during the earthquake. While the lower modes of vibration can be reliably identified from ambient vibration records, the frequencies of these modes are in each case higher than the corresponding frequencies derived from strong-motion response records. When soil-structure interaction is involved, the strong-motion model frequencies may range from 70 to 80 percent of the corresponding values extracted from ambient vibration records. Estimates of structural damping derived from ambient vibration data are substantially smaller than those derived from strong-motion data and are consistent with predictions of a damping model based on forced vibration tests. The lower bound of damping estimates obtained from strong-motion response records in this study is consistent with published data. Where soil-structure interaction is a significant factor, the overall damping for strong-motion response may be 3 to 4 times the indicated lower bound.