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Estimation of Ice Thickness and Strength for Determination of Lateral Ice Loads on Bridge Substructures in South Dakota

During 1998-2002, the U.S. Geological Survey (USGS), in cooperation with South Dakota Department of Transportation (SDDOT), conducted a study to evaluate factors affecting ice forces at selected bridges in South Dakota. The focus of this ice-force evaluation was on maximum ice thickness and ice-crushing strength, which are the most important variables in the American Association of State Highway and Transportation Officials (AASHTO) bridge-design equations for ice forces. Ice thickness was measured at six sites in South Dakota during 1999-2001 and ranged from 0 to 2.3 ft. Historical ice-thickness data measured by the USGS at eight selected streamflow-gaging stations in South Dakota also were compiled for 1970-97. Three ice-thickness-estimation equations that potentially could be used for bridge design in South Dakota were selected and included the Accumulative Freezing Degree Day (AFDD), Incremental Accumulative Freezing Degree Day (IAFDD), and Simplified Energy Budget (SEB) equations. An analysis of the data indicated that the AFDD equation best estimated ice thickness in South Dakota using available data sources with an average variation about the measured value of about 0.4 ft. Maximum potential ice thickness was estimated using the AFDD equation at 19 National Weather Service stations located throughout South Dakota. The estimated maximum potential ice thicknesses generally are largest in northeastern South Dakota at about 3 ft and are smallest in the southwest and south-central South Dakota at about 2 ft. Ice-crushing strength measured at the six sites from 1999 to 2001 ranged from 58 to greater than 1,046 lb/in² (pounds per square inch). From an analysis of the ice-crushing-strength data, ice-crushing strengths of about 1,000 lb/in² could be expected at any site in South Dakota if enough water is available for freezing and if the winter is as cold as the 2001 winter. Ice-crushing-strength data were evaluated to a limited degree to see how the ice-crushing strengths compared to the strengths used in bridge design in South Dakota. The ice-crushing strengths measured during spring breakup probably are the most applicable values for bridge design. The average ice-crushing strength measured near breakup at the six ice-data collection sites in South Dakota ranged from 75 to 300 lb/in². An ice-crushing strength of 250 lb/in² would not be anomalous for expected ice-crushing strengths near spring breakup in South Dakota. A more extensive ice-data collection effort is needed to accurately characterize ice thickness and ice-crushing strength for SDDOT bridge design in South Dakota. A direct measurement of ice forces acting on bridge structures also would be beneficial for bridge design.

Language

  • English

Media Info

  • Media Type: Print
  • Edition: Final Report
  • Features: Appendices; Figures; Maps; Photos; References; Tables;
  • Pagination: 122p

Subject/Index Terms

Filing Info

  • Accession Number: 01044305
  • Record Type: Publication
  • Report/Paper Numbers: SD98-04-F
  • Files: TRIS, USDOT, STATEDOT
  • Created Date: Mar 12 2007 3:39PM