Safety Inspection Assesses Condition of Longest Bridge in North Carolina

As bridge failures, deficient structures and crumbling infrastructure have made the national news for the last several years, North Carolina residents and visitors can breathe easy on their travels to and from the Outer Banks thanks to the safety inspection of the Virginia Dare Memorial Bridge. The structure connects the U.S. Route 64 bypass at Manns Harbor with Roanoke Island, and at over five miles long, is the longest bridge in the state and one of the lengthiest concrete bridges on the East Coast. In order to keep this heavily traveled four-lane structure safe for both locals and seasonal tourists, the North Carolina Department of Transportation (NCDOT) is required to have the bridge inspected every two years. Additionally, to address concerns about deteriorating transportation infrastructure, NCDOT has instituted an even more rigorous detailed inspection protocol than the core structural element inspection required by the Federal Highway Administration. KCI was tasked with completing the state’s first core element inspection of this signature crossing.

Working under an open-end contract, our team has successfully completed hundreds of bridge inspections for NCDOT; however under newer protocols, engineers were required to observe and document the size, material consistency and condition of each structural element of the bridge. With a short timeframe to get the work complete, KCI utilized several teams and an innovative management approach to overcome weather, traffic, equipment and data collection challenges.

The Virginia Dare Bridge provides the most direct access to the Outer Banks, which is responsible for a large percentage of Dare County’s $1 billion tourism-related economy. So, it was critical that KCI’s inspection in the field avoided impacting seasonal traffic. Typically when inspecting smaller bridges, our team is given one month to complete the work, but due to the size of the Virginia Dare Bridge, NCDOT asked that work begin after March 1st and be completed by April 30th.

With only a short window for completion, we had to develop and implement a strategy to tackle the voluminous amount of field work, extensive data collection and detailed report preparation. The schedule allowed little room for unforeseeable circumstances and conditions.

Liz Phipps, PEVice President, Practice Leader

Liz Phipps, PE

KCI’s initial plan was to utilize multiple inspection teams, minimizing the number of days needed in the field and maximizing days to write the report. However, engineers quickly realized that the data collection system they were using presented some limitations. Bridge inspections completed for NCDOT must utilize the state’s proprietary data management system called WIGINS – Wearable Inspection Grading Information Network System – to collect field observations and prepare the final report. Data for each structural element is entered into the system using a single pen tablet provided for each site. The system also requires that all data be entered for an individual span before moving onto the next. While the software improves the consistency of the data collection, and often eliminates inspectors from having to return to the office to file reports, the application’s design only allows for one inspection team to enter information at a time for each structure. The KCI team recognized immediately that the features of the WIGINS system that make it so efficient for inspection of routine bridges instead created major challenges for the Virginia Dare Crossing.

Because this was the first core element inspection for this structure, each element had to be identified visually and its material and dimensions noted and checked versus the original construction plans. With 268 spans and a very short allowable timeframe for the project, multiple inspection teams would have to work simultaneously to collect data on the nearly 11,000 structural elements that comprise the bridge. The structure’s curvature, skews and length further complicated the approach. Under-bridge access equipment was not wide enough for engineers to adequately inspect elements on both sides of each 68-foot-wide span. Logistic constraints for maintenance of traffic also limited the team to a single lane closure each day—meaning inspection of all core elements that make up a single span could not be completed before moving on to the next, as required by WIGINS.

Virginia Dare Memorial Bridge Drainage
The structure is composed of 268 spans and is constructed of 10,889 structural elements including 1,855,560 square feet of concrete deck; 1,610 pre-stressed concrete girders; 3,220 elastomeric bearings; 2,910 reinforced concrete end diaphragms; 536 reinforced concrete intermediate diaphragms; 15.2 miles of concrete barrier rail; two reinforced concrete end bents with 28 concrete piles; 233 concrete piers, which are supported on 1,591 concrete piles; and 33 concrete piers with 88 concrete columns supported by more than 2,000 pilings.

KCI and NCDOT programmers attempted to split the bridge up within the system to allow multiple teams to concurrently work on the structure using several tablets, but when that proved impossible, engineers developed a custom spreadsheet that would efficiently allow inspection findings to be collected simultaneously from multiple sources, yet still offer the ability to sort data by span and element for easy entry into WIGINS. With KCI’s customized approach established, engineers relocated to seaside towns for three weeks to complete the large-scale inspection.

Split into three teams, crews worked 10-hour workdays Monday through Thursday, with Friday available as a make-up day. Engineers utilized specialized equipment to access all of the bridges components, from every section of railing to each timber fender at the waterline.

Virginia Dare Memorial Bridge Underbridge Inspection
KCI’s plan called for two under-bridge inspection vehicles with a maintenance of traffic lane closure of up to one-mile. Safety boats, which were required while the under-bridge equipment was over the water, were able to contact approaching vessels in the channel by radio to alert them of ongoing inspection activity.

However, delays caused by equipment malfunction required teams to quickly change locations on the bridge. From logistic and reliability challenges with under-bridge equipment to malfunctions with crash vehicles and sign boards, delays resulted in a loss of 30 hours of equipment time. In addition, fog and high winds that surpassed equipment limitations led to additional work stoppages. To minimize the impact on the aggressive schedule, teams performed other tasks such as inspecting the pier caps, using the boats to perform soundings, and climbing ladders to access spans over wetlands.

Most individual bridges can be inspected in a single day, but the length of the Virginia Dare crossing stretched the schedule to three weeks. The entire deck had to be walked—meaning five miles in one direction, and then five miles in another.

Bob Pruett, PEProject Manager, Senior Structural Engineer

Bob Pruett, PE

These adjustments and working long hours, including Friday make-up days, allowed KCI to complete the field inspection on schedule. Report preparation took an additional five weeks, with engineers working nearly around the clock to cut and paste data from the custom spreadsheet into the WIGINS database. More than 1,400 photographs, totaling nearly six gigabytes of data, documented condition and defects and had to be uploaded into WIGINS for the final report.

Despite all of the unexpected circumstances, KCI inspected and documented every component of the structure and submitted the 1,500-page report in just 36 days.