U.S. timber railroad bridges is estimated to be about one third of total inventory of over 100,000. The timber components in these bridges have already exceeded their traditionally accepted life span of 50 years in many locations. AREMA (American Railway Engineering and Maintenance-of-Way Association) regulates allowable deflection of timber railroad bridges based on their span length. The existing methods to measure such bridge deflections are laborious, expensive, unsafe or limited.

This project demonstrated a non-contact technique to extract 2D/3D deflections of bridges that will be economical and safe for the timber railroad bridge owners. This project developed a linear feature based Deflection Measurement System (DMS) using Terrestrial Laser Scanner (TLS) and cameras. The requirement of control points to register images in conventional techniques was overcome by using the 3D model extracted from TLS in dead load condition of the bridge. The project developed 1) Deflection Monitoring System (DMS) with camera 2) Linear feature based registration methodology for the data collected by DMS and 3) Non-contact methodology to compute instantaneous 2D/3D deflections under live-load conditions.

The project team implemented the technique using CSX owned candidate bridges in South Florida. The results were compared and validated using other techniques including Finite Element Analysis. As a next step, the research team will collaborate with railroad bridge owners to incorporate this non-contact deflection monitoring technique in their regular maintenance practices.

The final report is available.