Forced Vibration Testing of an Expanded Base Concrete Pile

by Alex Sy, Klohn Leonoff Ltd, Richmond, Canada,
David Siu, Klohn Leonoff Ltd, Richmond, Canada,

Document Type: Proceeding Paper

Part of: Piles Under Dynamic Loads


Forced vibration testing of a full-scale cast-in-situ expanded base concrete pile supporting a structural mass was conducted as part of a test pile program for a paper mill expansion at a site near Vancouver, British Columbia. An electromagnetic shaker was used to generate random broadband and sinusoidal excitations to the mass in the vertical, horizontal and rocking modes. The random vibration testing provided a rapid, initial estimate of the natural frequencies of the system. The measured frequency response functions from the subsequent sinusoidal frequency sweep tests are compared to theoretical results calculated based on a plane strain approximate solution and measured in-situ shear wave velocity data. In the vertical and horizontal modes of vibration, the theoretical resonant frequencies are in good agreement with the measured values. In the rocking mode, however, the computed resonant frequency is higher than the measured value. The theoretical damping is too high for all modes. Reasonable match between measured and calculated responses is obtained by use of a weak zone to approximately account for the non-linear soil behavior adjacent to the pile and for pile-soil slippage or gapping. The analysis further suggests that the sequence of vibration testing can have an effect on the measured response.

Subject Headings: Wave measurement | Frequency response | Shear waves | Wave velocity | Soil structures | Soil-pile interaction | Soil-structure interaction | Concrete structures | British Columbia | Canada | Vancouver

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