InTrans / Jan 05, 2023

New traffic signal design developed at InTrans reduces wind-induced vibration, and costs

Project led by BEC Researcher Alipour now in implementation phase

City of Ames staff with PI Alipour monitoring a signal light structure at University Boulevard

A recently funded project led by Bridge Engineering Center (BEC) Researcher Alice Alipour will be implementing a recently developed traffic light signal that has proven to effectively mitigate vibration in traffic signal structures.

The modified traffic light design increases aerodynamic damping and reduces vibration of the traffic signal structure. The proof-of-concept was developed as part of the National Cooperative Highway Research Program (NCHRP) Innovations Deserving Exploratory Analysis (IDEA) program that explores the feasibility of unproven technical concepts. Now, as part of a follow-up NCHRP IDEA project, Alipour will test and try the developed idea on a full-size traffic signal structure.

“In the initial project, we introduced the first known effort to use the geometric characteristics of the signal light itself to mitigate the problem. Since wind is used to mitigate wind-induced vibrations, it will be able to mitigate the vibrations due to any type of wind,” said Alipour, who is also an associate professor at Iowa State University’s Department of Civil, Construction, and Environmental Engineering (CCEE). “In the recently funded follow up project, we get to expand the concept from the laboratory to a real-world environment by implementing it on a real-life structure.”

“Another unique aspect about this innovation is that by increasing the wind speed, the respective aerodynamic damping also increases, which results in more degradation of amplitude of vibrations,” said Partha Sarkar, who collaborated on the project and is an Iowa State professor of aerospace engineering. Alipour added, “In other words, it effectively uses wind itself to mitigate wind excitations in traffic signal structures.”

The novel solution is much needed given the wide usage of cantilevered traffic signal structures throughout the US that have experienced many instances of failure, typically attributed to the large amplitude vibrations caused by wind. Additionally, it adapts the signals themselves rather than the structures, meaning the solution is less costly.

Alipour is especially thankful for the support from two main collaborators: the Iowa Department of Transportation (DOT) and the City of Ames. She said, “They have been supporting this project from the very first day.”

“The economic implications of this approach are huge considering the millions of these structures that are being maintained by cities and state DOTs,” said Alipour. “This new strategy can be used as a mitigation technique for the existing structures, and by implementing it for new structures, it can help with savings on the structural system.”

Alice Alipour, right, with City of Ames and Iowa State University staff at the test signal installation