Low Cost Steel Bridge Pile Inspection Technology

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Low Cost Steel Bridge Pile Inspection Technology

Author: Hay, Thomas R | Size: 1.10 MB | Format: PDF | Quality: Original preprint | Publisher: Transportation Research Board | Year: 2008 | pages: 216

Inspection of steel bridge piles on a regular basis for the presence of defects is essential for the long-term safety of bridge infrastructure over water. Currently, these inspections are done visually and in the case of submerged piles, divers perform these inspections. Current pile inspections are performed by divers according to the National Bridge Inspection Standards and are dependent on inspector training, skill and experience. In many cases, significant sections of pile can not be visually inspected since they are submerged in environments that prevent visual inspection, such as swampy waters and river beds. Based on this feedback from railway bridge field engineers, there is a requirement for affordable pile inspection technology capable of providing feedback on pile wall loss. The ideal technology would be able to inspect submerged pile remotely from easy-to-access pile locations. The objective of this Innovations Deserving Exploratory Analysis (IDEA) project was to study the pile wall loss detection and characterization potential of long-range ultrasound (LRUT). Quantitative readings on remaining wall would be used to estimate pile remaining life and the load rating for the bridge. Laboratory studies were carried out to investigate the effectiveness of LRUT in detecting several types of manufactured defects in dry as well as H-piles submerged in water. In the laboratory tests, LRUT was able to detect manufactured defects, such as wall loss, through spliced and braced pile. Field testing was carried out on dry H-pile on a Norfolk Southern bridge in Mississippi and these data were used to develop Distance-Amplitude Correction (DAC) curves to quantify the wall loss (in ranges of 100%, 75%, 50%, and 25% wall loss). These ranges were established based on feedback from Norfolk Southern Railway and the performance limitations of the technology. Field testing on submerged H-pile was undertaken on a Norfolk Southern bridge in North Carolina. Of the eighteen LRUT measurements taken, slightly more than half fell within the established accuracy requirements, based on comparisons with actual measurements taken by divers.. Possible sources for the differences include the location at which the diver made the measurement, the severely-eroded pile surface above water, on which the electromagnetic acoustic transducer was mounted, inability of the current prototype to account for multiple inline wall losses, welded braces absorbing significant amounts of the ultrasound, and LRUT measurement error. As a direct result of this project, WavesinSolids LLC has developed the core technology to launch a commercial product and inspection service. Improvements in this core technology are underway to address the problems identified in the field tests.

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