Fatigue Design of Sign Support Structures for Loading Caused by Natural Wind Loads

Abstract

A unified design method for fatigue loading caused by natural wind for highway overhead sign support structures is needed. Whereas the fatigue design provisions given in the 2001 AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals provide fatigue design criteria for natural wind, these provisions are applicable only within certain limitations. A comprehensive approach was developed for fatigue design for the treatment of sign support structures, considering the dynamic properties of the structures such as the natural frequency and damping characteristics. The approach is applicable for structures in which the dynamic response can be approximated by a single degree-of-freedom system. Typical examples include cantilever-and bridge-type overhead sign support structures. The proposed fatigue design approach incorporates these parameters in a simplified, systematic procedure that can be readily used by the engineer. The analytical work performed involved principles relating to random vibration in use of the vibration response spectrum (VRS). The fatigue load was selected from the VRS in terms of the natural frequency of the structure, the critical damping percentage (a.k.a., damping ratio), and the annual mean wind velocity of the intended site.

Aerodynamics of Highway Sign Structures: From Laboratory Tests and Field Monitoring to Structural Design Guidelines

“…One recognized contribution to the instability of sign supports is vortex shedding caused by wind loading (Hosch and Fouad 2009;Connor et al 2012;Sherman and Connor 2019). A solid structure immersed in a fluid flow generates vortices in its wake.…”

Comprehensive investigation on the cause of a critical crack found in a diagonal member of a steel truss bridge

“…Wieghaus [13] proposed a probabilistic framework to estimate the fatigue life of a lightweight, wind-excited steel structures, and compared resulting wind-induced fatigue life distributions with compiled inspection records for a large traffic signal structure population. Hong [14] and Hosch [15] observed the fatigue failure of sign, luminaire, and traffic signal support structures caused by natural wind-induced vibration and developed a comprehensive approach for fatigue design. Alduse proposed [16] a Bayesian approach to estimate the wind-induced fatigue damage of long-span bridges while considering the uncertainties in the probability model and the parameter.…”