MnDOT recently entered into a contract with the University of Minnesota (UMN) to complete a research project to keep wind from damaging rural intersection conflict warning signs (RICWS) and other digital message signs (DMS).
The project is titled “Understanding and Mitigating the Dynamic Behavior of RICWS and DMS Under Wind Loading.” Lauren Linderman, assistant professor at UMN’s Department of Civil, Environmental and Geo-Engineering, will serve as the principal investigator. Jihshya Lin of MnDOT will serve as technical liaison.
“This project will find out the behavior of the DMS and RICWS under AASHTO defined design loads and develop the retrofitting system to avoid the experienced problems that will improve the public safety, reduce the maintenance cost and minimize impact to the traffic,” Lin said.
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.
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.
- Task 1A: Development of Field Instrumentation Plan and Instrumentation Purchase
- Task 1B: Experimental Determination of Load Effects and Dynamic Characteristics of Post Mounted DMS in Field
- Task 2A: Development of Numerical Models to Investigate Post Mounted DMS Sign Demands and Fatigue
- Task 2B: Validation of Numerical Models to Investigate Post Mounted DMS Sign Demands and Fatigue
- Task 3A: Investigation of Design Loads and Relevant Fatigue Considerations for DMS
- Task 3B: Analysis of Design Loads and Anticipated Fatigue Life of DMS
- Task 4: Experimental Determination of Dynamic Characteristics of RICWS in Field
- Task 5: Development and Validation of Numerical Models to Investigate RICWS Signs
- Task 6: Numerical and Experimental Investigation of Drag and Vortex Shedding Characteristics of RICWS Signs Using Scaled Models
- Task 7: Numerical and Small-Scale Experimental Investigation of Modifications to RICWS Sign Panel to Reduce Effects of Vortex Shedding
- Task 8: Numerical and Analytical Investigation of Noncommercial Means to Damp Motion of RICWS Blankout Sign Structure
- Task 9A: Research Benefits and Implementation Steps Initial Memorandum
- Task 9B: Research Benefits and Develop Implementation Steps
- Task 10: Compile Report, Technical Advisory Panel Review and Revisions
- Task 11: Editorial Review and Publication of Final Report
The project is scheduled to be completed in March 2019.