Understanding and Mitigating the Dynamic Behavior of RICWS and DMS Under Wind Loading

Status:  Active
Project Start Date:  05/10/2017


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) and the Digital Message Signs (DMS). RICWS 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 DMS, particularly the loads on the friction connection. This research project involves a field investigation to determine the structural performance of these two types of sign structures. Laboratory tests using a towing tank facility and a wind tunnel will be performed on scaled models and opportunely modified models to improve performance and minimize unsteady loads. Numerical models incorporating computational fluid dynamic structure interaction (CFDSI) will be validated with the field and laboratory data and used to investigate a variety of modification schemes. Analytical models 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 and DMS sign structures and to provide modifications to improve the structural performance of the RICWS sign structures while maintaining the crashworthy requirements. The results will help to ensure the uninterrupted service of these sign structures, which are important to public safety.

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