Date of Thesis

5-7-2015

Thesis Type

Honors Thesis

Degree Type

Bachelor of Science in Civil Engineering

First Advisor

Kelly A. Salyards

Abstract

The use of lightweight and slender elements in civil engineering design has been increasing, which in turn has increased the vulnerability of these flexible structures to vibrations. For proper functioning of such structures, it is important to accurately assess the dynamic properties of the occupied structure and to incorporate the effects of human-structure interaction (HSI) in the design process. The dynamic properties refer to natural frequencies, damping ratios, and mode shapes of the occupied structure. Human occupants are modeled as an additional degree-of-freedom on a single degree-of-freedom model of the structure. Modal analysis of the combined 2DOF system is used to determine the dynamic properties of the occupied structure. This small-scale study utilized previously collected experimental data, from a laboratory test structure built at Bucknell University, to assess the quality of a current method proposed for incorporating HSI into design. In addition, several current models aiming to represent the occupants are assessed through a comparison of modal properties obtained through a series of analytical models with the available experimentally determined properties. Finally, a parametric study is completed to ascertain the most appropriate occupant properties to simulate the experimental dynamic parameters. The results of this study show that the methodology proposed to incorporate the effects of HSI in design is accurate for the standing-straight occupant posture but not for the standing-with-bent-knees posture. Further, the methodology was not appropriate for seated occupant postures. Thus, the focus was to develop an appropriate seated occupant model that would accurately predict the experimental dynamic properties ascertained from the laboratory structure. Additional seated occupant models from the field of biomechanics were investigated which informed the range of occupant properties to be used in the parametric modeling. To this end, a Dynamic Graphical User Interface (GUI) that implements modal analysis in the frequency domain was developed in Matlab. A natural frequency range of 5.2-5.9 Hz and damping ratio range of 33-39% was determined. An incremental parametric modeling was completed through the use of a modified version of the GUI code. The results seem to indicate that the frequency of the occupant model should be in the 5.2-5.4 Hz range. However, the results do not definitively suggest a damping ratio for this model. Additional research is necessary.

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