The National Academies

NCHRP IDEA 20-30/IDEA 153 [Completed (IDEA)]

Laser Measurement Accelerated Retrofit System
[ NCHRP 20-30 (NCHRP-IDEA) ]

  Project Data
Staff Responsibility: Inam Jawed
Fiscal Year: 2011

This project was aimed at demonstrating the application of an advanced laser measurement technology to improve the bridge retrofit process by rapidly and accurately making field measurements of components and automatically producing engineering drawings. Work in the initial phase involved an assessment of the measurement process along with initial developmental testing and consisted of two main tasks. Task 1 defined the optimal method to integrate physical measurements into the retrofit process while Task 2 focused on implementing the system for actual field measurements. Task 1 included development of custom measurement plans and steps to automate measurements and data processing. Task 2 involved field measurements on bridges as well as preparation of custom hardware for implementing the system, including development of special mounts and fixtures for the laser system for optimal measurements. Work was coordinated with steel bridge fabricators and end-users to better understand the required measurements and to develop specifications and measurement processes. The system was implemented on multiple bridges with common retrofit issues. Specialized mounting fixtures to aid in measurements were designed, fabricated, and evaluated in laboratory and shop environments. The fixture design allows measurements under difficult hard-to-access situations under field conditions. Work in the final phase focused on field measurements with the system and using the new custom-designed mounting fixtures. Field tests were coordinated with suitable retrofit projects in collaboration with state DOTs in order to validate and refine measurement procedures.

The bridge retrofit laser system is driven to a bridge site in a vehicle, quickly setup, and used to make measurements on the bridge. No special targets are needed and the structure does not need to be directly accessed. Very accurate measurements can be made over very large distances. The laser system will measure the exact dimensions and spatial location of bridge details, including splice hole locations based on measurements of bolt or rivet heads. Based on the physical laser measurements, CAD design drawings will be automatically produced. These drawings can be used by an engineering design firm and fabricator to rapidly produce retrofit parts. High accuracy measurements are essential for retrofit measurements (gusset plates, trusses) where precise location of splice holes is needed.

The system has the potential to significantly reduce the time between the initial identification of a problem on a bridge and the repair and resumption of service of the structure. The system saves time and money by streamlining steps in the retrofit process in that laser field measurements can be used to automatically produce CAD drawings for fabricators. The system provides specifically processed engineering data and not just a cloud of points. The proposed system can make measurements with minimal impact at the bridge site. Measurements can typically be made without altering traffic under the structure (i.e. no lane closure). The system can make measurements over water or other difficult access conditions, such as rail lines. The final report provides project data and guidelines for field implementation of the technology.

The contractor's final report is available

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