Aeroelastic Testing of Span-Wire Traffic Signal Systems

Ziad Azzi,Arindam Gan Chowdhury,Amal Elawady,Manuel Matus,Peter Irwin,Ioannis Zisis

doi:10.3389/fbuil.2020.00111

Ziad Azzi, Arindam Gan Chowdhury + Show 4 more

Open Access

https://doi.org/10.3389/fbuil.2020.00111

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Abstract

Span-wire traffic signals are vulnerable to extreme wind events such as hurricanes and thunder-storms. In past events in the Southeastern Coast of the United States, many failures of span-wire traffic signals were reported. In order to identify their dynamic behavior during extreme wind events and investigate their buffeting response, a large-scale aeroelastic testing was conducted at the NHERI Wall of Wind (WOW) Experimental Facility (EF) at Florida International University (FIU). The WOW is a large-scale open jet wind testing facility, comprised of 12 fans, and capa-ble of simulating winds at speeds up to 70 m/s, corresponding to a Category 5 hurricane. Follow-ing the Froude number criterion, a 1:10 aeroelastic model of a span-wire traffic signal system consisting of two 3-section and one 5-section signals was designed and constructed, based on the properties of its full-scale counterpart. In the testing protocol, various wind directions ranging between 0 and 180 degrees were considered at full-scale wind speeds ranging between 21 m/s and 42.5 m/s. The results of the aeroelastic tests show a similar behavior compared with previous full-scale tests conducted at the WOW. However, an increase in the RMS of accelerations was observed in comparison with those from the full-scale tests. This is attributed to the fact that the aeroelastic model enabled better simulation of low-frequency eddies in the turbulence spectrum compared to the full-scale testing turbulence spectrum.

Highlights

Florida and the East Coast of the United States have been very vulnerable to extreme wind events such as hurricanes and thunderstorms
During the 2004–2005 hurricane season, it was observed that these systems were very susceptible to damages under windinduced forces, which indicated that a better design was required to enhance their survivability and sustainability (State of Florida Department of Transportation (FDOT), 2005; Cook et al, 2012; Zisis et al, 2016a)
Studies have focused on the effect of wind loads on untethered span-wire signal poles and recommended the consideration of load transfer induced by such forces, which can cause significant deflections to end supports (Alampalli, 1997)

Summary

Introduction

Florida and the East Coast of the United States have been very vulnerable to extreme wind events such as hurricanes and thunderstorms. Aeroelastic Testing of Traffic Signals such traffic signal systems consist of the signal units supported by aluminum hangers and two wires (a messenger on the bottom and a catenary on the top) holding the hangers in place and spanning between two poles (typically steel or concrete) Despite their wide use in the state of Florida, there is a lack of design guidelines for span-wire systems subjected to highintensity wind events (Cook et al, 2012; Irwin et al, 2016; Zisis et al, 2016a, 2017; Azzi et al, 2018, 2019; Matus, 2018). Other investigations examined the overall response of span-wire traffic signals with different parameters of the signal assembly itself and found out that such changes affect the drag and lift coefficients of the entire system (Matus, 2018)

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