In service fatigue fracture of highway signs and signal support structures due to wind induced oscillations is the primary concern for cost-effective life cycle performance of these structures. Recognizing the impact of potential life and property damage from structural failures and economic burden of inspecting, maintaining and replacing the sheer volume of these structures in the inventory, the American Association of State Highway and Transportation Officials (AASHTO) made significant revisions to the fatigue design provisions of these structures in the 2013 6th Edition of the Standard Specifications for Highway Sign Luminaire and Traffic Signal Structures, which were ported to the 2015 1st Edition of the LRFD specifications for the subject structures. These changes necessitated update to the standard designs and drawings. While the specification changes were based on significant research performed during 2000s, many of the connection details for the subject structures existing in the NJDOT inventory and standard drawings are not included in the specifications, but have performed satisfactorily in the field. One such example is the arm-to-pole clamp connection. In other instances, the structure sizes successfully used by NJDOT are outside the dimensional limits imposed by the specifications. As a result, NJDOT is expected to experience significant cost impact on account of upgrading of the existing inventory or due to non-compliance of the latest AASHTO specifications. An experimental and computational research project is proposed for investigating the fatigue performance of the connection details in the current NJDOT inventory and the existing standard drawings that do not meet current AASHTO specifications but have shown satisfactory performance over the years. In addition, alternate innovative sign and signal support structures employing bolted connections (instead of fatigue prone welded connections) are proposed to be investigated as part of this research for cost-effective fatigue resistant solution.
Idea No. 147