Bridge Inspections Combine Modern Technology with Traditional Techniques

As leader of a WSP bridge inspection team, Matt Sullivan leaves nothing to chance when safety is concerned — whether protecting his team while they work high above the ground, or when he makes the tough call to close hazardous bridges.

“I’ve only ever been part of four bridge closures in my entire 17-year career, but I closed two of them in the past month,” said Sullivan, PE, a vice president and structural engineer for WSP. “It was WSP’s first inspection of both bridges, and our team uncovered significant deterioration and section loss of the superstructure.”

Sullivan doesn’t have to look far to be reminded why his responsibility is critical. “I have a four-month-old child and I wouldn’t want him riding in a vehicle across any bridge in that condition,” he added.

Bridge safety is a top priority in the U.S., where nearly half of all bridges are at least 50 years old, and 7.5 percent of those are considered structurally deficient, highlighting the critical need for quality inspections by experts trained to reliably locate those flaws.

But with more than 617,000 U.S. bridges, that is no small undertaking.

More than 120 WSP inspectors nationwide conduct approximately 2,500 bridge inspections annually and have completed well over 100,000 inspections since the National Bridge Inspection Standards (NBIS) were established by the U.S. Congress in 1968. NBIS mandates thorough inspections of all U.S. bridges at least once every two years to maintain safe operations and prevent structural and functional failures.

WSP’s bridge inspectors work with state departments of transportation, federal agencies, bridge and port authorities, city agencies and municipalities to ensure that their structures meet or exceed the requirements of a safe, secure bridge.

“One team can complete 120 inspections of routine, local bridges with one-to-four spans annually, whereas larger signature bridges may require three-to-four teams – and as many as six – to complete over the course of an entire year,” said Frank DeOrtentiis, PE, vice president and deputy bridge inspection lead for the New York metropolitan area at WSP.

One of his key focus areas is load rating, which is a critical part of WSP’s inspection work. There are certain structural elements that are evaluated on every bridge. Depending on the specific details, condition and configuration of the structure, additional elements may also be inspected. All findings are then analyzed to ensure that the bridge can still safely support the loads imposed upon them.

“If some conditions require immediate repair, there might be a load restriction implemented where heavier trucks cannot use the bridge until the needed repairs are made,” DeOrteniis added. “It all boils down to public safety. That’s why we’re out there.”

Over the past decade as a special liaison to the firm’s national bridge group, Sullivan’s focus has been on inspecting everything from small culverts to well-known signature bridges.

“I lead inspections of some of the large suspension bridges in the Delaware and Philadelphia region. I also do a lot of our rope access work, too,” he said. Sullivan has   Level 3 certification, the highest level recognized by the Society of Professional Rope Access Technicians (SPRAT). This means he can oversee rope access worksites, the designing of rope systems and can provide advanced rescue aid.

Sullivan has seen an increase in work with WSP’s unmanned aerial systems programs – or drones — although, as an emerging technology for bridge inspections, its use has been limited.

“We use the drones as much as we can,” he said. “But, because our inspections are federally mandated and include federal regulations, we must adhere to certain requirements, in terms of our inspection processes.” Some inspections require a hands-on approach to ensure that specific things are being examined properly and correctly measured.

That’s where the use of ropes is necessary. “A drone simply can’t replicate that physical, firsthand approach,” Sullivan added. “That said, drones have proven to be a good addition to our toolkit.”

The main advantage to using drones is that they enable “eyes on” access to areas of a bridge that are difficult and time-consuming to reach, like concrete facades, large steel towers and cables that inspectors don’t have to physically handle. Visuals from the drone also provide clients with a clearer view of what inspectors discover in the field.

“We want our teams to be safe, so we limit our time in the roadway when we can and that’s another benefit of using rope access and drones,” DeOrtentiis said. “Once you’re on that rope, you’re not in a traffic lane. It also reduces traffic issues, so it benefits everyone.”

Sometimes when new problems are found during a bridge inspection, it’s because WSP has recommended a rope access inspection, which ensures that every single inch of the structure is examined. Often it results in the discovery of issues that have been undetected for years.

The decisions to replace bridges are usually made on a priority basis, due to limited funding and generally high replacement costs.

“It’s largely based on who the owner is,” DeOrtentiis said. “An owner that collects tolls usually will have a larger budget with a constant money stream and can afford preventive maintenance. For bridges where taxpayer funding is limited, the repairs that bring the structures up to code can often be more patchwork in nature.” 

“The federal government and the states do their best to maintain bridges, so they don’t have to be replaced, because replacing them is much more expensive,” Sullivan added. “If you spend $500,000 now to save $50 million 20 years from now, it makes sense, right? So, we see a lot of money invested in maintenance.

“Everything boils down to public safety,” he added. “It’s up to us to do a good job to catch potential problems early so that they can be repaired before the bridge reaches a point where closure is necessary.”