Civil Engineering ETDs

Tong Xia

Publication Date

9-10-2010

Abstract

This research primarily studies the effect of air on vibration of structures. Theoretical solutions based on various physics are derived and compared with experimental results to determine how air modifies the vibrational behavior of structures. This work may help in determining the characteristics of structural vibrations — from acoustic behavior to earthquake response - in practical buildings. The work consists of several primary components: derivation of theories that predict the effect of air on structural vibrations and vice-versa, design of experiments, and determination of the importance of air in structural vibrations and the applicability of different physics under various vibrational frequencies. Two types of physics - acoustic theory and fluid dynamics theory - are applied to derive solutions for damping ratios of air. Experiments such as an unbaffled plate experiment, a pendulum experiment and a baffled plate experiment are designed and conducted to observe the damping effect of air. Experimental results illustrate the applicability of the theories. Finite element analysis is performed to provide a computational basis with which to compare the observed vibrational frequencies. The main question in this research is whether air has a great effect on structural vibrations. The results show that air has a damping effect on vibrating buildings that can be important under certain conditions. The results also reveal that when calculating the damping effects due to air, different physics should be applied under different vibrational conditions. A dimensionless factor is derived to determine under which regimes acoustic theory is applicable, and under which regimes fluid dynamics theory is applicable.

Keywords

Structural dynamics, Vibration, Damping (Mechanics), Air pressure, Aerodynamics, Sound-waves, Acoustic radiation pressure, Fluid dynamics, Fluid-structure interaction.

Sponsors

United States Department of Energy National Science Foundation Sandia National Laboratories

Document Type

Thesis

Language

English

Degree Name

Civil Engineering

Level of Degree

Masters

Department Name

Civil Engineering

First Committee Member (Chair)

Ross, Timothy

Second Committee Member

Hayat, Majeed

Third Committee Member

Griffin, Steven

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