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Following on from the successful completion of the installation of specially tailored uplift bearings to replace the pin-and-link devices that originally secured the superstructures of the Delaware Memorial Bridge, the bridge’s twin suspension structures are currently undergoing a multi-year project to replace their numerous small-movement expansion joints. In line with the great care that the responsible engineers have taken to date in planning and implementing the renovation of this critically important transportation connection, the expansion joints to be installed throughout the two structures are being carefully evaluated before use.
The preferred expansion joint solution – the TENSA®POLYFLEX®Advanced flexible plug expansion joint – might be considered the vastly superior modern alternative to the traditional asphaltic plug joint. This joint type, which uses a special polyurethane (PU) material to form the driving surface, offers excellent long-term performance – thanks, for example, to its great strength and elasticity (with the material allowing 650% elongation before failure), and its resistance to both very low and very high temperatures – and also offers special advantages when used to replace old joints in existing structures with minimum impact on traffic. Thanks to these and its numerous other benefits, the TENSA®POLYFLEX®Advanced joint was selected for special consideration by the project’s engineers. But not content to rely only on the extensive testing to which it has been subjected in connection with its being awarded various national and international certifications, or its track record on structures around the world – including on similar cable-supported bridges in other countries and in other challenging applications in the United States – they decided to evaluate the expansion joint’s performance by means of trial installations on the bridge. This would enable them to gain experience in its use and greater confidence in its quality before proceeding to install it throughout the bridge’s twin superstructures.
In the course of the project, the option of also using – at selected locations – mageba’s newly developed alternative flexible plug expansion joint, the TENSA®POLYFLEX®RapidCure joint, was discussed and agreed upon in principle. The RapidCure version, which uses polymethylmethacrylate (PMMA) rather than polyurethane to form the driving surface, is very similar to the Advanced version. While both versions are very suitable for use in typical bridge renovation projects, where disruption to traffic must be kept to a minimum, the even faster-curing PMMA material of the RapidCure version is particularly beneficial in this regard – requiring only three hours to cure before being subjected to traffic.
The trial installations were done by way of two “pilot projects” – one using the original Advanced version of the joint to accommodate movements of about 40 mm, and another using the newer RapidCure version for larger movements of up to 105 mm. Following completion of the first pilot project (using the Advanced version) in November 2020, and of the second pilot project (using the RapidCure version) in October 2021, with excellent performance of the installed joints observed to date, the path is clear for these two versions of the TENSA®POLYFLEX® expansion joint to be installed throughout the bridge’s parallel superstructures in the coming years.
Owner: Delaware River and Bay Authority
Contractor: J.D. Eckman, Inc.