Date of Award

Fall 2003

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Civil, Construction, and Environmental Engineering

First Advisor

Foley, Christopher M.

Second Advisor

Heinrich, Stephen M.

Third Advisor

Schaefer, Matthew

Abstract

Highway sign support structures are rather innocuous structures when compared to the architectural and engineering marvels that fill the urban skylines in many cities across the globe. Though these structures are visually bland, they consist of a complex framework, which only recently has begun to be understood. This thesis provides a firm foundation for the analysis and fatigue evaluation of full-span highway sign support structures. The research this thesis is based upon was motivated by the seemingly "poor'' fatigue performance of full-span highway sign support structures in Wisconsin. This research endeavor consists of analysis and fatigue evaluation of a test group of full-span highway sign support structures found along Wisconsin roadways. While this study has a Wisconsin "flavor" to it, its methodology and conclusions are applicable to most any type of highway sign support structure. An extensive literature review is included, which summarizes the current state of highway sign support structure research. The studies and reports referenced are primarily devoted to cantilevered sign and signal support structures. The present study utilized these previous research endeavors as a steppingstone for the research of full-span sign support structures. The results and conclusions provided by the present study were generated analytically. A detailed discussion of the analytical models is provided. This discussion includes modal analysis as well as development of the supported sign and catwalk models. Future research, including testing of actual in-service structures to measure their dynamic characteristics (i.e. damping, vibrational frequencies, etc.) should be used to qualify the present study's analytical models and results. Numerous studies over the past decade have been devoted to quantifying and qualifying the truck-pulse loading. The source of this loading is wind pressure generated by semi-trailer trucks passing beneath sign support structures. The magnitude of this pressure and its impact on the design and analysis of highway sign support structures have been debated continually since the advent of the truck-pulse loading scenario. The present study contains an analysis of the test group structures subjected to a truck-pulse loading function that was developed from field measurements of a previous research effort. Discussion of this analysis and its results is provided. The Thesis includes discussion of wind loading including both galloping stability and vortex shedding. By using the aerodynamic stability criterion, the susceptibility of the test group structures to galloping instability is addressed. Vortex shedding is also evaluated. The remainder of the chapter is devoted to the study of natural wind gusts. Wind simulations are developed and used to perform time history analyses of the test group structures. Results data is then used in the fatigue evaluation of these structures. Current design standards are used to assess fatigue and fatigue damage accumulation in the test group structures. Results data from the truck-pulse loading and the wind loading analyses are used to quantify yearly fatigue damage to make service/ fatigue life predictions for these structures.

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