The National Academies

NCHRP IDEA 20-30/IDEA 127 [Completed (IDEA)]

Instrumentation to Aid in Steel Bridge Fabrication
[ NCHRP 20-30 (NCHRP-IDEA) ]

  Project Data
Staff Responsibility: Dr. Inam Jawed

Most states require a steel bridge fabricator to shop assemble some or all parts of a steel bridge. This practice is intended to assure that the structure, primarily the splice plates and cross frames, will fit together at the job site as designed. In many cases, during initial girder fabrication the splice plate holes are subdrilled at a dimension smaller than the final hole size needed for a splice plate bolt. To make sure all holes are aligned, the fabricated girders with subdrilled holes are then shop assembled, a splice plate is placed on the girders, and the holes are reamed to their final size. After shop assembly verifies proper fit-up of components, the bridge is disassembled and taken to the job site. This procedure is labor- and time-intensive and adds significant cost to a steel bridge. The application of laser-based metrology instrumentation to measure the exact size and shape of fabricated bridge girders, including splice plate hole locations, could potentially be used to aid in the fabrication of steel bridges. A laser-based instrument could be used in a fabrication shop to measure each girder after it was fabricated. Precise measurements of splice plate hole locations could be measured and documented. After all separate girders in a bridge have been measured with this laser-based instrument, this data could then be used to virtually assemble the bridge. Fabricated dimensions of the girders could be checked against shop or design drawings. The position of splice plate holes between girders could be checked to ensure proper alignment. Full-sized holes could be placed in girders during fabrication, eliminating the need to subdrill holes and shop assemble girders. All of the bridge assembly could be performed virtually, without physical shop assembly. Additionally, a complete record of the dimensions of a fabricated girder could be created. This record could be used as a quality control tool to detect fabrication errors prior to shipment to a job site.  (NTIS#PB2009-109001)

The final report for this IDEA project can be found at:

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