AN INVESTIGATION OF ACCURACY OF INERTIAL INTERACTION
ANALYSES WITH FREQUENCY-INDEPENDENT IMPEDANCE
COEFFICIENTS
Yilmazok, Ö / zgü / n
M.S., Department of Civil Engineering
Supervisor: Assoc. Prof. Dr. B. Sadik Bakir
November 2007, 79 pages
The inertial interaction between the soil and structure alters dynamic response
characteristics of a structure due to foundation deformability, such that the
flexibility and energy dissipation capability of surrounding soil may lead to a
significant increase in period and damping of structural oscillations. The inertial
interaction analyses can be accomplished through utilisation of frequency
dependent foundation impedance coefficients that are reported in literature for
various soil conditions and foundation types. However, such analyses should be
performed in frequency domain, and applicable to only cases that linear
structural response is considered. Alternatively, equivalent frequencyindependent
foundation impedance coefficients can be employed, such that a
constant excitation frequency is assumed in calculation of these coefficients.
In this study, it is assumed that the fundamental frequency of a fixed-base
structure, which can be obtained through employing available empirical
relationships or a modal analysis, can be substituted for excitation terms in
impedance expressions. The error induced in calculation of peak structural
distortions is investigated through comparisons of structural response due to frequency-dependent and frequency-independent foundation impedance
coefficients. For analyses, a linear single-degree of freedom oscillator is
considered for modeling the structure. The frequency-dependent impedance of a
rigid disk foundation resting on elastic halfspace is simulated by a limited
number of discrete elements. The response calculations are performed in
frequency domain, through employing 72 acceleration records.
It is concluded that, the natural frequency of fixed-base building can be
considered as effective excitation frequency for calculation of foundation
impedance coefficients, when the effect of inertial interaction on structural
response is moderate. Through employing equivalent-linear approximation for
the structural response, it is shown that the conclusion is also valid in cases that
nonlinear structural response is considered. However, when the inertial
interaction has more profound effects on the structural response, the use of
natural frequency of flexible-base structure, which is calculated iteratively due to
its dependence on foundation-impedance factors is recommended.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12609030/index.pdf |
| Date | 01 November 2007 |
| Creators | Yilmazok, Ozgun |
| Contributors | Bakir, Bahadir Sadik |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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