Bridge Scour Research Project

1. Bridge Scour Research Project Project Team Abstract Model Features • KNOWLEDGE GAPS IN HEC 18 METHODS • Relationships are not sensitive to the broad range of soil and rock textures actually encountered at bridge sites, leading to over-prediction of • scour depth in some situations. • Bed sediments consisting of very coarse granular particles, e.g. cobbles, boulders, are not addressed ; these typically exhibit high resistance to • erosion and low susceptibility to scour. • Actual field performance of a bridge over time clearly plays a role in scour analysis. However, longevity is not included in HEC-18 analyses. • Practice of using envelope curves to predict maximum scour depth is increasing in the U.S. and around the world; there is minimal treatment • of these in HEC-18. • New Jersey SEM Erosion Classes for Soil and Rock New Jersey Envelope Curve and Equation • (Developed from USGS Data) NJDOT Research Customer: Scott Thorn, P.E. Research Project Manager: Nazhat Aboobaker, Ph. D., P.E. NJIT Robert Dresnack, Ph. D., P.E. Josh Tooker, E.I.T. Eugene Golub, Ph. D., P.E. Melissa Salsano, E.I.T. Ali Khan, Ph. D., P.E. Shu Yi Tham John Schuring, Ph. D., P.E. Piotr Wiszowaty, E.I.T. William Pennock • The overall objective of this research is the development of a new approach for evaluating bridge scour for New Jersey's bridges. Study results include: • Web-based survey of scour practice within the U.S. • A new Scour Evaluation Model (SEM), which is a tiered, • parametric, risk-based decision tool, featuring: • »Geotechnical, hydrologic, and hydraulic data are analyzed • to generate risk ratings for a bridge. • »Ratings are inputted into a Risk Decision Matrix to • generate a scour priority level and recommended actions. • New Jersey SEM provides standard protocols for: (1) erosion • classification of sediments; (2) application of scour envelope • curves; and (3) analysis of hydrologic data. • Model was validated and calibrated by comparing actual field • observations with model results. • Model reflects New Jersey’s unique geology and hydrology, • although it can be recalibrated to other regions or states. • Model is principally designed for existing bridges, but some • components are also useful for new bridges. Acknowledgements New Jersey Department of Transportation U.S Department of Education New Jersey Institute of Technology NJIT McNair Staff The Scour Team Survey of Other States Q1: Have you had any bridges that have failed due to scour, including outright failures or preemptive replacements? Q2: In your experience, what are the most prevalent types of erosion that have caused failure and/or created potential danger of failure? Q3: In the light of your experience of different types of bridge scour, is there a need to modify current HEC-18 design procedures? Q4: What scour procedures and equations do you use in the design of new bridges? Q5: What scour procedures and equations do you use in the evaluation of existing bridges? Example Model Application Bridge Scour Module 1 Module 2 Module 3 Geotechnical Analysis Hydrologic/Hydraulic Analysis Risk Decision Matrix Module 4 Recommended Actions “Scour is an effect of erosive action of flowing water, which excavates and removes material from the channel bed, the bank of streams, and around the piers and abutments of a bridge.”