Delaware Memorial Bridge First and Second Structures, Dehumidification of Main Cables and Anchorages Design-Build

The Delaware Memorial Bridge (DMB) consists of twin span suspension bridges that are 3,650′ long with 2,150′ main spans. AB completed the superstructure and cables for the first span in 1951 and the second in 1969. In 2016, AB was back at the familiar site to install a main cable dehumidification system. At the time, the bridge was only the second in the U.S. to receive this technology. The modified design-build project’s goal was to protect the main cables from the effects of corrosion by lowering the relative humidity (RH) to acceptable levels.

AB’s scope of work included the design, installation, commission, and maintenance of the main cable dehumidification systems on both bridge structures. Given dehumidification’s relatively new status in the North American market, AB’s project team implemented creative concepts in sequencing the work, sealing the main cables, and troubleshooting the completed system to meet the DRBA’s needs. This was done by utilizing our experience on various rehabilitation and cable-supported bridge projects. This experience aided in painting operations, removal and re-installation of main cable shielding, and suspender replacement work on the DMB. AB also utilized team members who had worked on similar projects in the United Kingdom. Their experience helped the team with the dehumidification process and established ties with specialized plant and control integration contractors.

AB was also responsible for jacking and replacing 58 suspender ropes at 29 panel points that were shown to have corrosion. AB’s in-house engineering department designed the truss jacking system, temporary supports, and main cable roller nests for the suspender rope replacement. Throughout the project, AB continuously examined ways to execute the job in a safer and more efficient manner. On the previously completed dehumidification projects, movable gantry platforms had been utilized to access main cables. This required all dehumidification and cable band-related work in a single panel to be completed before moving to the next panel. On the DMB, AB worked with subcontractor Safespan, to design and install a full-length access platform that remained in place on all main cables throughout the duration of the project. This allowed crews to work safely and efficiently.

This project received an Award of Merit in the Highway/Bridges category from Engineering News-Record.