All ETDs from UAB

Advisory Committee Chair

Fouad H Fouad

Advisory Committee Members

Talat Salama

Virginia Sisiopiku

Houssam Toutanji

Nasim Uddin

Document Type

Dissertation

Date of Award

2009

Degree Name by School

Doctor of Philosophy (PhD) School of Engineering

Abstract

The 2001 edition of the American Association of State Highway and Transportation Officials (AASHTO) Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals has been revised in its entirety through a major research project conducted under the auspices of the National Cooperative Highway Research Program (NCHRP 17-10). A major part of the revision included updated provisions and criteria for extreme wind loads and new provisions and criteria on fatigue design. These provisions differ considerably from those in previous editions of the specifications, and have remained relatively unchanged in the 2009 edition. The impact of the fatigue criteria on the design of overhead sign structures has not been fully evaluated. The fatigue design loads do not adequately reflect the stresses gen-erated on these structures from wind-induced fatigue loading. In addition, the provisions do not account for the variety of support structures in design, each with different configuration, sizes, shapes, and material properties that influence vibration behavior. As a result, the vulnerability of sign support structures to wind-induced fatigue loading is not fully realized. The main goal of the project was to conduct theoretical and experimental pro-grams of study to evaluate the performance of cantilever-type highway overhead sign support structures subjected to wind induced fatigue loads. A theoretical program was developed that took into account the variety of sign supports structures in design, as well as addressed the vulnerability of these structures to wind-induced fatigue loading. The experimental program was developed to evaluate the accuracy of the theoretical study. A finite element analysis program was conducted to simulate the wind-induced loading en-vironment and the response of sign support structures to this environment. Alterations were made to the model that could not be done experimentally due to costs and time re-straints. The results of the finite element analysis were compared to the theoretical and experimental programs of study. The developed information and criteria on fatigue design of sign support struc-tures were used to develop fatigue design loads to provide an improved and more reliable design method. Recommendations are made to update the current specifications to in-clude more reliable fatigue loads.

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