Date of Thesis

Spring 2024

Description

There is a limited understanding of the impact that passive human occupants have on a dynamic structural system, referred to as Human-Structure Interaction (HSI). Cantilevers are naturally prone to excessive vibrations due to their long unsupported spans, and cantilevered structures such as those commonly found in the seating area of a stadium facility or concert hall are designed to support a high density of occupancy.

This study determined that HSI in cantilevered structures can be modeled using a simple two-degree-of-freedom system. The results of the model were validated by data that was collected on a small-scale laboratory structure intentionally designed to replicate the typical frequency range of cantilever stadium structures. The simplified model identified the dynamic properties of a passive, standing crowd to be 7.7 Hz and 22% critical damping.

Additionally, this study identified that the spatial distribution of a crowd occupying a cantilever has a large impact on the change in the dynamic response. Occupants that are closer to the tip of the cantilever reduce the first mode of natural frequency in a system much more than occupants that are located further away from the tip of the cantilever. Thus, a method was proposed in order to approximate the impact of a large, distributed crowd with occupants spaced along all parts of the cantilever by considering the center of mass of the lumped crowd and the mass participation ratio of the empty structure.

Finally, results were presented that show the decrease in frequency in cantilevers occupied by large crowds. It was determined that some cantilevers can experience a reduction in the first mode of frequency by as much as 30% when heavily occupied. This reduction in frequency should be considered in the design of cantilevered structures in order to avoid excessive vibrations that could cause discomfort for the occupants or difficulty operating equipment and machinery.

Keywords

human-structure interaction, civil engineering, structural engineering, vibration

Access Type

Honors Thesis

Degree Type

Bachelor of Science in Civil Engineering

Major

Civil Engineering

First Advisor

Kelly Salyards

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