Real Time Measurement of Scour Depths Around Bridge Piers and Abutments

Details

• Creators:
  Khan, Abdul A. ; Atamturktur, Huriye S.
• Corporate Creators:
  Clemson University. Glenn Department of Civil Engineering
• Corporate Contributors:
  South Carolina. Dept. of Transportation ; United States. Federal Highway Administration
• Subject/TRT Terms:
  Accuracy Bridge Abutments Bridge Piers Field Tests Flood Damage Measuring Instruments Monitoring Real Time Information Research Hub Scour Sensors State Of The Art Time Domain Reflectometers Turbulence

  More +
• Publication/ Report Number:
  FHWA-SC-14-05
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States
• Edition:
  Final report
• Corporate Publisher:
  Clemson University. Glenn Department of Civil Engineering
• Abstract:
  Scour is one of the most significant threats to bridge infrastructure and is the leading cause of failure within the United States. Scour monitoring is an approved countermeasure as reported by the Federal Highway Administration. As the monitoring techniques available range from simple devices that rest on or in the channel bed to advanced scanning systems that provide a bed contour profile, a concise study of the state of the art in real time scour measurement capabilities is required. The available techniques for monitoring scour are reviewed to highlight the governing physics, to evaluate field performance, and to identify the effect of environmental factors on accuracy and reliability. From this assessment, two devices are selected for further study: a sonar fathometer and a Time Domain Reflectometry (TDR) device. A novel device, called a Vibration-based Turbulent Pressure (VTP) sensor, is proposed which exploits the turbulence in open channels to locate the bed level. This sensor vibrates at significantly higher amplitude when in the channel flow relative to an identical sensor located in the sediment. The vibration-based method, time domain reflectometry, and sonar devices are evaluated against simulated field conditions in order to determine their relative sensitivities to environmental conditions. These tests reveal that sonar and time domain reflectometry devices can be influenced by channel salinity and temperature. In addition, the sonar device is shown to be sensitive to the suspended sediment concentration in the channel, its height relative to the bed, and bed topography within the sonar beam. The vibration-based method is shown to be the least sensitive to environmental factors in the channel. In addition, the VTP device can provide reliable results in highly misaligned flows. Finally, the performance of TDR, sonar, and the vibration-based technique is evaluated under field conditions. The field tests reveal that all instruments perform at their accuracy level. The sonar must be deployed close to the bed to guarantee that the beam will be contained within the scour hole and would not have large width. In addition, the site should not have high suspended load concentration. The TDR is insensitive to suspended sediment; however, salinity greater than 0.5 parts per thousand renders the instrument inoperable. The VTP is proven to be insensitive to all the environmental factors. However, field deployment reveals that debris accumulation may cause the instrument to report false bed location.
• Format:
  PDF
• Funding:
  SPR 692
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:88cd544e72cd1b74485835b000e25b7b18636a67b88752a019dec9f1128c7108
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/31100/dot_31100_DS1.pdf
• File Type:
  [PDF - 3.73 MB ]