Sydney Gateway SB51 Twin Bridge

High-precision strain and vibration monitoring with welded gauges and accelerometers, safeguarding structural performance for Sydney Airport’s new twin-arch bridge

The Sydney Gateway SB51 Twin Bridge Project

The Sydney Gateway SB51 twin bridge is a key part of Sydney’s infrastructure upgrades, connecting the city’s motorways to Sydney Airport. The project includes two large twin-arch bridges over Alexandra Canal, built to handle up to 10,000 heavy vehicles daily.
Each bridge uses over 3,500 tonnes of Australian steel and spans 108 meters in length and 26 meters in width. Once complete, it will provide a seamless, traffic-light-free route between major motorway interchanges and the airport.

The Challenges

The SB51 bridge project poses several technical challenges critical to ensuring its durability and effective monitoring. One primary challenge is the precise installation of welded dynamic strain gauges to measure fatigue from variable loads. Another significant challenge is capturing accurate vibrational data from the bridge cables to estimate the loads they bear, crucial for understanding the structural demands on the bridge and identifying any early signs of strain.

What We’ve Delivered

From 2023 to 2024, Sixense developed a custom, high-precision monitoring system for the SB51 twin bridge on the Sydney Gateway to support precise fatigue life calculations and ensure long-term safety. The system includes 24 welded strain gauges to track dynamic loads, eight 3D accelerometers on key cables to monitor vibrations, and temperature probes to assess environmental impacts
on performance. With high-frequency data collection, this setup provides engineers with a constant stream of data that enables proactive maintenance, preserves the bridge’s integrity, and supports smooth traffic flow, strengthening the reliability of Sydney’s key airport link