Design of Overhead VMS Structures for Fatigue Loads

2011PDFTech ReportFHWA/CA/OR-09203Variable message signsOverhead traffic signsFatigue (Mechanics)Load testsWindGustsResearch HubWeatherEnviornmentSignsDesignUnited StatesUniversity Transportation Center for AlabamaFouad, Fouad H.Hosch, Ian E.University of Alabama. Dept. of Civil, Construction and Environmental EngineeringNTL-HIGHWAY/ROAD TRANSPORTATION-HIGHWAY/ROAD TRANSPORTATIONNTL-OPERATIONS AND TRAFFIC CONTROLS-OPERATIONS AND TRAFFIC CONTROLSNTL-SAFETY AND SECURITY-Highway SafetyUS Transportation CollectionThe 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 includes 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. The impact of the fatigue criteria on the design of highway overhead variable message sign (VMS) support structures has not been evaluated and is not currently being implemented by the Alabama Department of Transportation (ALDOT). The main goal of the proposed work was to conduct an experimental program to develop realistic loading criteria for the use in fatigue design of bridge-type overhead VMS support structures. The study addressed fatigue loading related to natural wind and truck-induced wind gusts. An efficient step-by-step design methodology was formulated and made available from the established fatigue loading. The data analyses involved fundamental principles related to Structural Dynamics. Design examples with associated commentary are provided that describe the methodology and application of the fatigue loading criteria developed from this study. Recommendations for fatigue design of overhead VMS support structures were made