Understanding and mitigating the dynamic behavior of RICWS and DMS under wind loading

Principal Investigator:

Lauren Linderman, Assistant Professor, Civil, Environmental and Geo-Engineering

Co-Investigators:

  • Cathy French, I.T. Distinguished Professor, Civil, Environmental and Geo-Engineering
  • Michele Guala, Assistant Professor, SAFHL - Hydraulic Lab
  • Dominik Schillinger, Assistant Professor, Civil, Environmental and Geo-Engineering

Project Summary:

MnDOT districts have an interest in better understanding the structural behavior and ensuring the required performance of two types of sign panels and supporting structures: Rural Intersection Conflict Warning Signs (RICWS) blankout signs and the Type A post mounted Digital Message Signs (DMS). RICWS blankout signs have exhibited excessive swaying under wind loads, leading to safety concerns regarding failure of the support structure at the base. It is believed the heavy weight of these signs has brought the frequency range of these systems too close to that of the wind excitations. There is a need to investigate the wind-induced dynamic effects on these sign structures and to propose modifications to the systems to reduce the likelihood of failure. There is also interest in investigating the dynamic behavior of the post mounted DMS, particularly the loads on the friction connection and the fatigue lifetime. This research project involves a field investigation to determine the structural performance of these two types of sign structures. Numerical models incorporating computational fluid dynamic structure interaction (CFDSI) will be validated with the field and laboratory data and used to investigate the loading on post mounted DMS and RICWS blankout sign support; for the RICWS, a variety of modification schemes will be considered using the CFDSI based numerical models. Laboratory tests using a towing tank facility and a wind tunnel will be performed on scaled models of the RICWS and opportunely modified models to improve performance and minimize unsteady loads. Analytical models of the RICWS based on the numerical results will be generated to optimize potential noncommercial damping strategies. The outcome of this project is expected to develop an understanding of the RICWS blankout and post mounted DMS sign structures, provide guidance on the DMS Type A support design, and to propose modifications to improve the structural performance of the RICWS blankout sign structures without altering the structural supports. The results will help to ensure the uninterrupted service of these sign structures, which are important to public safety.

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