Use of Ambient Vibration Measurements to Infer Dynamic Properties of PoorlyCharacterized Old Earth Dams – A Case History from Puerto Rico

摘要

This paper presents a case history involving the seismic evaluation of the Patillasearth dam constructed in 1914 in southeast Puerto Rico. The dam is located in aregion of high seismicity and like many old structures there was little or noinformation regarding the properties and compaction levels of the different materialsused for the construction of this dam. This paper presents a description of theprocedure used to estimate the material properties for the seismic analyses of PatillasDam, with emphasis on the maximum shear modulus (G_(max)). The paper presents acomparison of the predominant vibration period of the dam in the transverse directionestimated using three different equivalent linear models for the dynamic finiteelement analyses and the values obtained from ambient vibration measurements usingaccelerometers placed at the crest of the dam. The resulting predominant periods forthe finite element models (T = 0.42, 0.49 and 0.56 s) had very good agreement withthe field tests (T = 0.43 to 0.45 s). The proposed methodology of using ambientvibration testing to help calibrate dynamic models of poorly characterized old damsproves to be promising.