Computational Fluid Dynamics Investigation of High Mast Illumination Poles: Influence of Light Fixtures

The Kansas DOT has recently discovered numerous failures of galvanized high mast illumination pole (HMIP) structures along major highways, particularly in western areas of the state. The majority of the failures have been characterized by cracks at the handhole detail, near the pole base. Many of the failed poles were installed in the past 8-12 months, and thus the failures are deemed extremely premature. The severity and speed of the failures is alarming, especially considering that collapse of an in-service HMIP near major highways such as I-70 poses great risk to the traveling public. Known failed structures have been removed from service, and KDOT is contracting with an outside party to perform holistic inspections of fatigue-sensitive details on poles across the state inventory to determine whether cracking exists in other HMIP structures. Additionally, a project is currently underway at the University of Kansas to characterize the failures and to determine fatigue implications of the current HMIP design and possible design modifications. The failures appear to be at least in part caused by wind-induced fatigue loading, and a number of KDOT’s HMIPs have exhibited “locked in” resonant frequency responses, such that they experience very large cyclic deformations under wind loading (on the order of 5’ of deflection at the tip of a 100’-tall pole). KDOT engineers recorded videos of multiple HMIPs exhibiting locked-in resonant behavior in March 2019 during a windstorm. Finite element models performed as part of the KU research showed that this type of repeated large-deformation response has the potential to produce severe fatigue damage over a very short amount of time. Therefore, there is a clear need to develop an understanding of what conditions produce this behavior so that actions can be taken to keep it from occurring. To develop a complete understanding of what conditions produce locked-in resonant responses, sophisticated aeroelastic analysis utilizing fluid-structure interaction (FSI) models are ultimately needed. FSI modeling can be used to explicitly capture the interaction between wind loading and dynamic structural behavior. However, FSI models are extremely resource-intensive, and they require careful development and tuning of variables beforehand. Before a FSI investigation can be responsibly performed, aerodynamic analysis based on computational fluid dynamics (CFD) modeling should be first completed, to ensure that the fluids component of the later FSI modeling is well-developed and valid. Additionally, the project team needs to be confident in our selection of variables to investigate in FSI models, and preliminary work is needed to determine whether variables such as HMIP luminaire type have a significant influence on the fluid dynamic response. In CFD models, the geometry of a structure is modeled which remains fixed while a fluid (i.e., air) flows around the rigid structural components at specific velocities. As geometric parameters of the HMIP are varied across different CFD models (e.g., luminaire type), it will be apparent if these variables have an influence on airflow around the pole. This is a critical first step to establishing a set of meaningful variables to be investigated in later fluid-structure interaction models.

Language

• English

Project

• Status: Active
• Funding: $100000
• Contract Numbers:

  RE-0797-01

  C2153

• Sponsor Organizations:

  Kansas Department of Transportation

  Eisenhower State Office Building
  700 SW Harrison Street
  Topeka, KS  United States  66603-3754
• Performing Organizations:

  University of Kansas Center for Research, Incorporated

  2291 Irving Hill Drive, Campus West
  Lawrence, KS  United States  66045
• Principal Investigators:

  Bennett, Caroline

  Collins, William

• Start Date: 20190901
• Expected Completion Date: 20241231
• Actual Completion Date: 0

Subject/Index Terms

• TRT Terms: Failure; Fatigue limit; Fluid dynamics; Lighting equipment; Structural mechanics; Support poles; Wind
• Subject Areas: Bridges and other structures; Highways; Maintenance and Preservation;

Filing Info

• Accession Number: 01856807
• Record Type: Research project
• Source Agency: Kansas Department of Transportation
• Contract Numbers: RE-0797-01, C2153
• Files: RIP, STATEDOT
• Created Date: Aug 30 2022 4:04PM