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Experimental observations of the effect of foundation embedment on structural response

Lin, Albert Niu (1982) Experimental observations of the effect of foundation embedment on structural response. EERL Report, 82-01. California Institute of Technology , Pasadena, CA. (Unpublished)

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Ambient, ring-down, and forced vibration tests were used to determine the effect of foundation embedment on the response of a one-story model structure 10 ft square in plan and 11.4 ft high. The tests, conducted at the full-, half- and unembedded foundation conditions, led to the identification of the fundamental translatory mode in the primary (east-west) and secondary (north-south) directions, and two torsional modes. The forced vibration consisted of horizontally incident SH-waves generated at an excitation structure located 47.5 ft (center-to-center) away. During these tests, detailed measurements of the near-field ground motion and modal displacement ratios were obtained at the fundamental mode in the primary direction. The displacement ratios were used to calculate the structural and foundation-soil stiffnesses and damping coefficients for comparison to theoretical results. Foundation embedment increased the model frequencies and decreased the contribution of the foundation motion to the overall displacement of the superstructure. For the fundamental mode response, which consisted of translatory and rocking motions, the resonant frequency predicted by lumped parameter analysis was higher than that measured experimentally by 25% for the unembedded case. While the experimental and theoretical fundamental mode shapes were in close agreement, the calculated effect of embedment on the response was less than that measured. These results were consistent with the comparison of the impedances and embedment factors. Serious discrepancies between analytical and experimental results were found for the case of torsion; a simple two-degree-of-freedom model was consistent only with the first of the two measured resonant frequencies.

Item Type:Report or Paper (Technical Report)
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URLURL TypeDescription ItemAlso published as author's PhD thesis
Additional Information:PhD, 1982: PB-84-163252
Group:Earthquake Engineering Research Laboratory
Series Name:EERL Report
Issue or Number:82-01
Record Number:CaltechEERL:1982.EERL-82-01
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Usage Policy:You are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format.
ID Code:26364
Deposited By: Imported from CaltechEERL
Deposited On:25 Sep 2001
Last Modified:20 Aug 2021 23:41

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