Post-Tensioned Special Inspection (PTSI) on the Lyne Rail Bridge.
In February 2019, following the global safety concerns raised by the Genoa Bridge collapse, HTA was commissioned to perform a high-priority Post-Tensioned Special Inspection (PTSI) on the Lyne Rail Bridge. This complex cable-stayed, post-tensioned structure required a comprehensive audit to CS465 standards to verify its structural integrity and ensure the safety of both the rail network and the M25 motorway below.
The project was a logistical feat, requiring the total closure of the M25 to facilitate safe access for inspections. Simultaneously, the team had to operate within the Rail Network’s highly restrictive night-time possession windows. The structural design combining post-tensioning with cable stays demanded specialised access and the coordination of multiple teams working under intense time pressure and high-stakes safety conditions for Network Rail, Osborne, and Arcadis Consulting.
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Post-Tensioned Special Investigations (PTSI): Rigorous structural auditing to CS465 compliance.
Magnetic Flux Leakage (MFL): A UK-first application to detect corrosion within cable stays.
Ground Penetrating Radar (GPR): High-resolution imaging to locate tendon ducts at depth.
Ultrasonic Tomography: Advanced NDT to assess the grouting condition of detected tendons.
Possession & Traffic Management: Coordinating works across full motorway closures and rail possessions.
HTA pioneered the use of Magnetic Flux Leakage in the UK to provide definitive data on the internal condition of the cable stays. By integrating this with GPR and Tomography, our teams were able to locate tendon ducts with surgical accuracy and assess grout quality far more efficiently than traditional methods. This data-driven approach allowed HTA to deliver a comprehensive safety assessment for Network Rail on schedule, proving the effectiveness of innovative NDT in managing critical national infrastructure.
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