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Experimental Observations of the Effect of Foundation Embedment on Structural Response

Citation

Lin, Albert Niu (1982) Experimental Observations of the Effect of Foundation Embedment on Structural Response. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:05162018-100416743

Abstract

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:Thesis (Dissertation (Ph.D.))
Subject Keywords:Civil Engineering; Environmental Engineering Science
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Civil Engineering
Minor Option:Environmental Science and Engineering
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Jennings, Paul C.
Thesis Committee:
  • Housner, George W. (chair)
  • Babcock, Charles D.
  • Brooks, Norman H.
  • Jennings, Paul C.
  • Scott, Ronald F.
Defense Date:17 May 1982
Funders:
Funding AgencyGrant Number
CaltechUNSPECIFIED
NSFPFR77-23687
Earle C. Anthony FellowshipUNSPECIFIED
Record Number:CaltechTHESIS:05162018-100416743
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:05162018-100416743
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10896
Collection:CaltechTHESIS
Deposited By: Melissa Ray
Deposited On:02 Jul 2018 23:34
Last Modified:02 Jul 2018 23:34

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