Trends Summer 2017 - Page 17

A A four-phased system yres Associates and GCI, Inc., in partnership with Kimley-Horn and Associates, Inc., and STV Incorporated, recently earned a National Recognition Award in the American Council of Engineering Companies 2017 Engineering Excellence Awards competition for their efforts evaluating scour for more than 1,500 Florida bridges with unknown foundations. The following describes the four levels of evaluation typically completed. Phase 1 involves a field review of the bridge, looking at conditions, the Bridge damage after flash flood in Colorado Springs, Colorado water’s angle of attack, its channel migration, and other field evidence suggesting a scour problem. Bridges appearing to look scour-susceptible advance to a Phase 2 hydraulic evaluation where engineers complete a channel survey and hydraulic modeling and calculate a Undermining of abutment by scour theoretical amount of bed material that the force of the water will remove. If it’s doubtful there’s enough material left to support the foundation, then a Phase 3 evaluation is performed. This involves geotechnical and structural evaluations to check the bridge’s stability and determine whether the predicted scour could potentially cause it to become unstable in a major storm. If the latter is the case, engineers then implement Phase 4 and develop a plan of action. When working with unknown foundations, additional steps, such as non-destructive evaluation or theoretical formulations to estimate pile embedment, are required. I I mporting Innovation n 2001, Ayres engineers Pete Lagasse and Paul Clopper traveled to Germany to investigate and assess a partially grouted riprap technique that had been developed and perfected there. They then adapted what they learned into practice back in the United States. Tidal surge at Shad Creek Bridge near Jacksonville, Florida “We routinely look at what the state of practice is not just in the United States but all around the world – and then supplement that,” said Clopper, director of applied technology at Ayres, who’s currently leading $800,000 worth of research projects in conjunction with the National Cooperative Highway Research Program (NCHRP). In 2010, Lagasse and Clopper proposed using the innovative and ultimately cost- saving European technology on a scour-critical bridge in Colorado Springs, Colorado. Permeable and flexible, it offered decided advantages over traditional, fully grouted rock – including providing greater protection against storm events at a lower cost. The original design with standard techniques was bid at $140,000 and provided protection up to a 50- year flood. The change to partially grouted, or “matrix” riprap, cost $47,000 and provided protection against a 500-year flood. Matrix riprap uses smaller rock and grout within the riprap to provide stronger and more stable protection compared to traditional loose (dumped) rock. The Colorado Springs project represented the first use of the partial grouting technique in the United States for bridge scour protection. │17