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Jean–Louis Briaud, Observation Method for Bridge Scour
March 1, 2016 @ 6:00 pm - 8:30 pm
2016 Geo-Institute Cross Country Lecture and University of Washington Hennes Lecture
Dr. Jean-Louis Briaud
Distinguished Professor, Texas A&M University
President of FedIGS
6:00pm – Lecture, Alder Commons
7:30 pm – Reception, Kane Hall, Walker Ames Room
University of Washington, Seattle
Lecture and Reception:
free, no registration required
One bridge collapses every ten days in the USA and 60 % of the time it is due to scour. Bridges are inspected every two years; those with foundations that are unstable for calculated and/or observed scour conditions are termed scour critical bridges. There are approximately 17,000 scour critical bridges in the United States. This lecture proposes a new bridge scour assessment method called the Observation Method for Scour (OMS). The proposed method does not require site specific erosion testing and accounts for time dependent scour in erosion resistant materials. The OMS works in four simple steps. First the maximum observed depth of scour Zmo recorded at the bridge site is obtained; this typically comes from inspection reports. Second the maximum observed flow velocity Vmo that the bridge has been subjected to is calculated; this is done by using USGS gages records and an interpolation technique. Third, knowing Zmo and Vmo, the value of the future scour depth Zfut for a chosen velocity Vfut is calculated; this is done by using equations and charts developed for that purpose. Fourth the Zfut value is compared with the acceptable depth of scour for the bridge and a decision is made as to the safety of the bridge should it be subjected to Vfut. Ten case histories are presented.