The objective of this paper is to present a universal approach for determining the design fatigue load due to truck-induced wind gust for highway overhead sign support structures. The fatigue load is determined based on the dynamic properties of the structure. It is applicable for structures where the dynamic response can be approximated by a single degree-of-freedomsystem. Typical examples include cantilever- and bridge-type overhead sign support structures. The developed approach incorporates these parametersin a simplified systematic procedure that can be readily used by the engineer. Principles relating to mechanical vibration and utilization of the shock response spectrum were used to determine the load. The fatigue load is selected from the shock response spectrum in terms of the natural frequency of the structure and the speed of the truck. Comparisons were made with the current truck-induced gust fatigue design provisions given in the 2009 AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals. Additional comparisons were made with dynamic finite element analysis of a modeled support structure.
Abstract