Scour at Contracted Bridges (2006) / Chapter Skim
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Pages 112-123
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101 CHAPTER 4: CONCLUSIONS AND SUGGESTED RESEARCH The main purpose of this research was to collect field data from which processes affecting scour magnitude in contracted openings could be identified, to support verification of physical- and numerical-model studies, and to improve guidelines for applying scour-prediction methods at contracted bridge sites. Field data collected from 15 sites in this study were added to the National Bridge Scour Database (BSDMS)
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102 Factors Not Included In Laboratory Models (1) To date (2004)
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103 2001) is problematic because the hydrodynamic mechanisms that induce the individual scour components work together.
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104 (7) The clear-water scour equations grossly over-predicted field observations by 2 to 40 times the measured scour depth.
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105 roughness and topographic variation; floodplain flow obstructions; valley geometry, including valley width variation and slope; roadway crossing geometry – roadway profile, embankment geometry and orientation, and bridge length; embankment protection; and duration and frequency of flood flows.
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106 Numerical Models (13) The flow conditions and resulting scour patterns at contracted bridges are often too complex to be represented accurately by one-dimensional hydraulics and current (2004)
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107 as at the beginning of a flood and during the scouring process, the one-dimensional model is severely limited in its ability to accurately distribute the flow.
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108 observed width of debris accumulations on the observed pier; however this was based on data from only one site. RECOMMENDATIONS Although additional real-time data collection would be beneficial, the collection of large volumes of field data sufficient for developing regression or semi-empirical equations for abutment and contraction scour would be difficult and expensive.
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109 14, this approach is only appropriate for regional applications; however, a large data set with a broader range of conditions may provide a more detailed assessment of the limits of scour given a variety of different conditions. The result could be a simple method or family of curves that would provide the maximum observed scour for various site conditions.
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110 (2) No detailed real-time measurements were collected during conditions where the bridge superstructure is partially or completely submersed, because of the difficulty and hazards in measuring scour these conditions.
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111 (7) Additional research should be conducted on the geometry of debris accumulations to extend and support the methods proposed by Diehl and Bryan (1997)
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112 large number of bridges. The research on the effect of vegetation should be given a higher priority.
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