Bridges
The marine environment for civil engineers is challenging because infrastructure below the waterline is subject to hydraulic forces and environmental conditions. These can severely degrade the condition of the asset, yet the infrastructure is difficult to inspect and assess.
The Federal Highway Administration, the Association of Civil Engineers, the US Army Corps of Engineers, and the US Federal Government publish manuals that are dedicated to the inspection, assessment, and reporting requirements.
Highway and rail bridges that span waterways are subject to scour from hydraulic forces of river flows. Scour occurs due to river and tidal flows. The flow rate can vary dramatically from slack tide to full flow, or from normal to high rainfall conditions. Scour can cause sudden catastrophic failure of bridge piers, which is why the US Army Corps of Engineer’s bridge inspection manual, the US Government’s Congressional Federal Regulations for railroad bridges and the Federal Highway Administration focus on the importance of inspecting bridge piers for scour.
While these manuals offer general guidance, sensor technology has advanced so quickly that several tools available today aren’t documented in these reference manuals.
KONGSBERG sensors provide benefits to civil engineers and contractors responsible for infrastructure inspe¬ction and reporting.
KONGSBERG is a pioneer in applying underwater acoustic technology for visual inspection of marine infrastructure. It seems like magic, really – KONGSBERG’s acoustic instruments create high-resolution pictures underwater, using sound. Further, KONGSBERG’s sensor software can correct distortion to the sonar images by accounting for temperature, salinity, and pressure effects that affect the speed of sound in water.
The resultant images are the highest-resolution images available on the market. New developments in sensor technology, sonar deployment, unmanned and autonomous deployment platforms, and image processing software provide civil engineers and contractors with new tools. They can leverage these tools to do their complicated jobs faster, more reliably, and with superior deliverables for their clients.
Scour monitoring
“A PROBLEM OF NATIONAL SCOPE: Scour at bridges is a problem of national scope and is not limited to a few geographical areas (table 1). Scour of the streambed near bridge piers and abutments has resulted in more bridge failures than all other causes in recent history (Murillo, 1987)” report.pdf (usgs.gov).
Many of the nation’s bridges cross rivers or channels that are exposed to varying current flows depending on season and storm events. As climate change increases the intensity and frequency of storms, the potential for scour of bridge piers and abutments also escalates. Kongsberg has solutions for periodic and persistent inspection of bridges. As the threat of scour intensifies, there are now options of installing permanent sensors that monitor scour on a continual basis. Authorities who have responsibilities for multiple bridges can now monitor scour from multiple locations to central operation rooms for full situational awareness of their entire network and react to alarm conditions accordingly.
Structural inspection
Underwater bridge inspection
“The U.S. has 614,387 bridges, almost four in 10 of which are 50 years or older. 56,007 — 9.1% — of the nation’s bridges were structurally deficient in 2016, and on average there were 188 million trips across a structurally deficient bridge each day. While the number of bridges that are in such poor condition as to be considered structurally deficient is decreasing, the average age of America’s bridges keeps going up and many of the nation’s bridges are approaching the end of their design life” (Bridges-Final.pdf (infrastructurereportcard.org). Within the US, the Federal Highway Administration and the US Army Corps of Engineers define bridge inspection requirements and frequencies and compulsory reporting.
Kongsberg equipment has been actively used to augment conventional diver bridge inspection since the late-1980s for collecting two-dimensional bottom and vertical structure imagery. Subsequent Kongsberg equipment developments now allow inspection teams to collect images with unprecedented resolution and generate three-dimensional point cloud data of underwater piers and abutments, even in zero visibility and high current flow conditions where there are significant risks when deploying divers.
Underwater infrastructure inspection
“Out of sight, out of mind.” Sadly, this phrase is often indicative of the inspection of subsurface components of marine infrastructure where divers are traditionally deployed to complete the inspections. Another issue is whether the diver has the specialized training to complete the inspection. Add to that poor or zero visibility, and many diver inspections have to be completed by touch alone. This is a recipe for failure in detecting subsurface structural deficiencies.
The American Society of Civil Engineers Manual 130 - Waterfront Facilities Inspection and Assessment outlines the use of high-resolution imaging scanning sonar for infrastructure inspection. Sonar ‘sees’ through zero in-water visibility; today’s high-resolution sonar can produce near photographic imagery and are used for overall structure assessment and to augment diver inspections.
Unlike when using sonar, water intakes must be locked out before diver inspection. Acoustic inspection is completed at a standoff distance and effectively accomplished while the facility is fully operational; discharge outfalls/pipes can be scanned under full flow to reveal if the ports are functional, thus never jeopardizing a diver’s safety or impeding production.
Monitoring underwater infrastructure will always remain “Out of sight” but Kongsberg provides solutions for “Never out of mind!”
