Uplift upgrade

State-of-the-art uplift bearings have now been installed to replace the antiquated pin-and-link devices that originally secured the superstructures of the Delaware Memorial Bridge.

The Delaware Memorial Bridge in the United States, twin suspension bridges connecting the states of Delaware and New Jersey across the Delaware River, were constructed with a pair of upright pinned links supporting the end of each superstructure at each tower. After over fifty years of service it was decided to replace this support system at all 16 locations, implementing a modern structural bearing solution instead. This significant change to the bridges’ superstructure support concept presented a number of challenges for the structural bearing design and supply, including large movements and rotations, load reversals with high uplift forces, and high long-term accumulated movements. The bearings were also required to temporarily (but not permanently) resist transverse forces, and to be designed for integration in the bridge’s monitoring system, with sensors to measure loads, displacements, rotations and loss of sliding material thickness due to wear.

Fortunately, mageba already had very useful experience in supplying a solution for a very similar project just two years earlier, at the Forth Road Bridge in Scotland. Applying that experience to meet the project’s requirements, mageba proposed a solution based on the tried-and-trusted RESTON® SPHERICAL bearing, with pre-integrated sensors for connection to the bridge’s structural health monitoring (SHM) system. Details of the requirements are provided on mageba’s project reference sheet, and the bearings’ design is illustrated by the attached images.

With the bridge bearings having now all been installed, the Delaware Memorial Bridge’s superstructures are optimally supported at each end using modern technology. The equipping of the structural bearings with sensors of various types for integration in the bridge’s SHM system, enabling online presentation of recorded data and immediate notification of unexpectedly high or low values of any variable, will also contribute to the maintenance and long-term proper performance of the bridge bearings in the structure, and to a degree, of the bridge as a whole. With these high-spec bearings installed to replace support mechanisms of a very different type, the project demonstrates how exceptional engineering structures, and extraordinary bridges in particular, often require unique, innovative solutions – solutions which can only be provided by suitably experienced suppliers.

“Frequent uplift (tension-compression) loads require a well thought detailed design given the high risks & costs associated with repair / replacement of uplift bearings. We are proud to have collaborated with HNTB and the DRBA in developing a custom solution and supply first of its kind uplift spherical bearings in the USA, equipped with a monitoring system. Fabrication in Asia, thorough load testing in Europe, and final installation by the American Bridge Company in the USA ended up being a truly global collaboration in successful execution of this challenging project.”

Amit Kutumbale, Technical Manager – Bearings, mageba USA

Owner: Delaware River and Bay Authority
Contractor: American Bridge Company
Engineer: HNTB Corporation

The Delaware Memorial Bridge consists of two parallel structures of length 10,764 ft [3,281 m] (main span 2,148 ft [655 m]), constructed in 1951 & 1968 respectively, connecting the U.S. states of New Jersey & Delaware across the Delaware River

At each tower, the superstructure at each side was supported by an original pin-link system that had experienced significant corrosion and wear over the years

It was decided to replace all 16 pinned links with modern uplift bearings – transferring changing downward and uplift loads, accommodating movements and rotations, and even providing temporary transverse fixity during the bridge renovation work

3D design representation of a main span bearing, with movement capacity +/-23 inch [+/-585 mm] and weighing 6.0 tons (side span bearings similar but with lower movement capacity)

Sample images from finite element analysis at local part level

Sample images from finite element analysis at global assembly level

The marked parts are removable and replaceable, enabling the structural bearing to be adapted as required to allow or prevent transverse movements (preventing during the bridge renovation work)

A fully assembled main span structural bearing, complete with “folding sheet” protection of the stainless steel sliding plate beneath along which the upper moving part slides

Testing, including uplift (tension) load testing, cyclic tension/compression testing (simulating load reversals) and horizontal load testing (shown), was carried at an independent testing facility in Germany

Lowering of a side span bridge bearing into position

Installation of one of the 16 new bridge bearings, equipped with pressure sensors to measure loads, tiltmeters to measure rotations, displacement sensors to measure movements and proximity sensors to measure wear of sliding material, on a new support bracket

Snapshot from the monitoring system’s web user interface showing presentation of recorded data