Intelligent Infrastructure Systems and Pennoni were responsible for the hands-on emergency inspection of the superstructure and substructure of Spans 11 through 14 and Pier 15 of Bridge 1-813. The bridge, located in Wilmington, DE, is comprised of twin structures carrying northbound and southbound Interstate 495 with independent multi-beam superstructures and independently supported hammerhead piers under each half of the structure carries 90,000 vehicles per day.
Within 40 minutes of being alerted to the problem by DelDOT, Intelligent Infrastructure Systems engineers were onsite to assess the condition of the bridge. Transverse rotations up to 4 percent from their original position were observed in Piers 11 through 14 causing the median barriers to be vertically out of alignment by as much as 17 inches, which was visible from the roadway. It was later determined that this rotation was a result of a large earth embankment (estimated at 50,000 tons) placed immediately adjacent to the structure, causing compression of the underlying soft soils and lateral pressure on the bridge foundations.
The bearings, field splices, cross frame connections, deck joints, top of deck, hammerhead pier caps, and pier columns were all inspected hands-on to assess any damage caused by the global rotations/movement of the structure and measurements were collected to document these rotations/movements. In addition, open pits were excavated along the south faces of the foundations of Piers 11 through 14 exposing the full height of the footing and approximately 18-inches of the piles beneath the footing for inspection.
Tilt sensors were installed on Piers 10 through 15 to continuously monitor the pier rotations via real-time data collection and data was collected within 12 hours of the initial call from DelDOT. Duties included extensive coordination with DelDOT’s Bridge Management section, coordination with access equipment providers, oversight and management of all field operations (inspection and monitoring), hands-on inspection of Spans 11 through 14 and pier foundations/piles, supported DelDOT’s Survey section with collecting survey points on the structure, attendance and participation at internal DelDOT coordination meetings, preparation of interim daily reports of conditions found, and preparation of a final comprehensive emergency inspection report.
The bridge was re-opened to traffic within two months. Intelligent Infrastructure Systems continues structural monitoring services during the construction of the permanent pier replacements. Intelligent Infrastructure Systems will install long-term monitoring and continue monitoring services after construction is completed.