Engineers' Society of Western Pennsylvania

Location

337 Fourth Avenue
Pittsburgh, PA 15222

Phone: (412) 261-0710 Email: eswp@eswp.com Get Directions

Monday, July 14, 2025

Featured State Session

Details coming soon!

 

Suspension Bridges Session

Time: 1:30 – 3:00 PM

IBC 25-04: NDT-inspection and Residual Lifetime Assessment of the Lysefjord Suspension bridge with more than 2000 Main Cable Wire Fractures
Tobias Friis, Ramboll, Copenhagen S, Denmark

Setting a new benchmark in bridge maintenance, this study delves into the structural health of the Lysefjord Bridge, a suspension bridge spanning 446 meters across Lysefjord in Rogaland, Norway. Featuring a construction with each main cable comprising six parallel laid prefabricated full locked coil cables, the bridge has seen over 2000 wire fractures in just 25 years of service, prompting a rigorous evaluation of its integrity and future viability.

Conducted by Ramboll in 2023 and 2024, this research unfolds in two pivotal segments. Initially, a special inspection combined state-of-the-art non-destructive testing techniques—Magnetic Rope Testing and Guided Wave Ultrasound Testing—with traditional visual assessments to thoroughly evaluate the external and internal condition of the bridge’s cables. This phase not only assessed the current state of wire breaks but also reviewed historical inspection data to trace the evolution of these fractures from the bridge’s inception to the present, aiming to predict future deterioration patterns. The work describes how the uncertainty arising from a lack of agreement between visual inspections and NDT-inspections is assessed to estimate a likely number of total wire fractures of around 2500.

Subsequently, the project tackled the challenging task of estimating the bridge’s residual service life. This comprehensive evaluation employed a variety of engineering approaches, from metallurgical analysis to probabilistic assessments and simulations, underpinned by advanced bridge and cable models. The result is a nuanced understanding of the bridge’s residual lifetime, culminating in strategic recommendations for maintaining its structural health and safety.

IBC 25-05: Constructing the Benjamin Franklin Bridge’s Dehumidification System
Joshua Pudleiner, AECOM, Philadelphia, PA; Elisabeth Klawunn, Delaware River Port Authority, Camden, NJ; Tyler Pritz, AECOM, Philadelphia, PA; Elizabeth Lucchesi, AECOM, Conshohocken, PA

The Benjamin Franklin Bridge opened to traffic on July 1, 1926, and was the longest suspension bridge in the world with a main span of 1,750 until the opening of the Ambassador Bridge in 1929. The bridge carries Interstate 676/US Route 30 over the Delaware River, connecting the cities of Philadelphia, Pennsylvania and Camden, New Jersey and is owned and operated by the Delaware River Port Authority (DRPA), a bi-state agency.

Following a main cable internal inspection in 2016, the DRPA decided to install a cable dehumidification system on the bridge to prevent corrosion from occurring in the high-strength steel cable wires. In late 2019, a five-part $195 million rehabilitation project began where Part 1 included main cable and anchorage dehumidification, cable band bolt replacement, and acoustic monitoring installation. Parts 2-5 consisted of steel repairs, painting, decorative lighting, and walkway widening/rehabilitation.

Cable dehumidification is a complex blend of structural, mechanical, electrical and controls engineering. It involves the injection of dry air into the cable microenvironment to remove water and sustain relative humidity below a critical threshold where corrosion practically ceases. To date, the Benjamin Franklin Bridge is the fifth bridge in the U.S. and first known previously oiled cable to have had a cable dehumidification system installed.

The project is anticipated to reach substantial completion on schedule in early 2025. The paper will present the project work including best practices to guide bridge owners who are considering the installation of cable dehumidification systems.

IBC 25-06: A Case Study on the Replacement of OSPD Deck Panels on an Existing Suspension Bridge
Dillon Betts, COWI North America, Halifax, Nova Scotia, Canada; Jorge Perez Armino, COWI North America, Halifax, Nova Scotia, Canada; Aaron Ferguson, COWI North America, Halifax, Nova Scotia, Canada

The A. Murray MacKay Suspension Bridge opened to traffic in 1970 and carries four lanes of traffic over the Halifax Harbour between Dartmouth and Halifax. The suspended structure of the bridge is approximately 740 meters in length and deck system comprises longitudinal stiffening trusses, transverse floor trusses and an orthotropic steel plate deck (OSPD). The OSPD consists of approximately 231 panels which are spliced together with hundreds of thousands of bolts. Each OSPD panel is approximately 9.6 m long and 5.5 m wide.

Recently, the OSPD panels have been shown to be susceptible to fatigue and some panels have experienced fatigue cracking. To address these fatigue concerns, the owner mandated that spare replacement panels be designed and fabricated. Though the exact dimensions of the existing panels vary along the bridge, the panels were designed and detailed the OSPD replacement panels as modular such that they could be used to replace the majority of the existing panels on the bridge. Additionally, HHB decided to move forward with the replacement of two panels on the bridge. Each panel replacement was completed successfully in single weekend bridge closures to mitigate the effect on local commuters.

In this paper, the replacement of two existing OSPD replacement panels is presented including the overall panel design approach, the development of the erection procedures and the structural analysis of the bridge during erection.

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Special Sessions

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