Evaluation of Bridge Scour Research (2012) / Chapter Skim
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NAtioNAl CooperAtive HigHwAy reseArCH progrAm Responsible Senior Program Officer: E.T. Harrigan August 2012 C o n t e n t s Introduction, 1 Research Results Proposed for Adoption by AAsHto, 2 Pier Scour Processes and Predictions, 2 Abutment and Contraction Scour Processes and Predictions, 5 Geomorphic Processes and Predictions, 8 Proposed Future Research studies, 16 Pier Scour Processes and Predictions, 19 Abutment and Contraction Scour Processes and Predictions, 20 Geomorphic Processes and Predictions, 23 References, 23 evAluAtIon oF BRIdge sCouR ReseARCH This digest summarizes key findings of NCHRP Project 24-27(01)
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2dation material in which the pier is sited. Of these variables, effective pier width and flow depth are of prime importance because they determine the overall structure of the flow field.
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3poral development of scour entails significant uncertainty. Prediction (not design estimation)
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4flow depth and pier width (in a vertical cross-sectional plane transverse to the pier and a plane streamwise to the pier)
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5method (Sheppard et al.
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6that are not satisfied for bridge contractions (which are inherently short contractions, and for which the flow is non-uniform)
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7needed. It could in theory be applied to scour Classes I, II, and III channels (where Class I refers to narrower bridge crossings of incised channels; Class II to wider bridge crossings, where the channel is typically compound; and Class III to bridges spanning wide braided river channels)
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8or HEC-RAS with controls on reasonable values of input parameters would be very helpful. A long-term field program of obtaining highquality, real-time field data should be undertaken.
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9table 2 Current practice based on type and level of analysis. Level of Analysis Level 1 – Assessment (qualitative or conceptual)
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10 table 3 Strengths and weaknesses of proposed methods in geomorphology topic. Result (Reference)
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11 table 3 (Continued)
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12 table 4 Strengths and weaknesses of proposed methods in site reconnaissance topic. Result (Reference)
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13 and headcuts. Sediment deficiency results when an imbalance exists between the sediment supply and the sediment transport capacity in a river reach.
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14 Channel Migration Channel migration is the specific term for changes through time in the location of the channel of a watercourse that occur because of retreat of one bank at an erosion rate that is approximately matched by advance of the opposite bank through accretion. Channel migration results in lateral movement of the channel across the floodplain, either through incremental shifting at a rate related to channel width or more rapid relocation of the channel through an avulsion.
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15 Vegetation Influence on Migration (Perucca et al.
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16 a meandering planform into a braided channel (with extreme widening) , or vice versa (with extreme narrowing)
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17 table 7 Strengths and weaknesses of proposed methods in the change in channel width topic. Result (Reference)
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18 table 8 Strengths and weaknesses of proposed methods in sediment dynamics topic. Result (Reference)
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19 Similar to the classification used in NCHRP Project 24-8 (Parola et al.
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20 table 12 Research topics and priorities for considerations complicating scour depth estimation. Topics Priority Design Issues -- Common Pier Forms Reliable shape and alignment factors for common pier forms.
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21 table 13 Prioritized list of research and education needs addressing improved understanding of abutment scour processes. Aspect Research Need Priority Laboratory Studies (L)
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22 table 15 Prioritized list of research and education needs addressing improved methods for monitoring and maintenance. Aspect Research Need*
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23 geomorphic Processes and Predictions Table 16 lists prioritized research needs related to the overall topic of geomorphic processes and predictions. Two of the eight research needs are assigned critical priority.
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24 spill-through abutments. Journal of Hydraulic Engineering 132(3)
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25 Journal of the American Water Resources Association 43(5)
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ACKNOWLEDGMENTS This study was performed under the overall guidance of the NCHRP Project Committee 24-27. The Committee is chaired by RICK RENNA, Florida Department of Transportation.
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Transportation Research Board 500 Fifth Street, NW Washington, DC 20001 These digests are issued in order to increase awareness of research results emanating from projects in the Cooperative Research Programs (CRP)
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