Many of the railroad bridges in the United States were built in the early 1900s or before. Time and tonnage have taken their toll on these structures, and railroads today are confronted with the necessity to replace them or upgrade them with selective replacement of critical components. The situation with highway bridges is similar in terms of need for repair, rehabilitation, or replacement.

This project involved the manufacturing and testing of a prototype Hybrid-Composite Beam (HCB) bridge for railroad and highway applications.  The hybrid-composite beam is comprised of three main sub-components: a shell, compression reinforcement and tension reinforcement.  The compression reinforcement consists of self-consolidating concrete which is pumped into a profiled conduit within the beam shell.  The tension reinforcement consists of Hardwire® steel reinforcing fabrics which run along the bottom flanges of the beams. 
 
 Whereas fiber-reinforced plastic (FRP) materials are generally too expensive and too flexible when arranged in a homogeneous form, the strength and stiffness of the HCB are provided by a more efficient use of materials that are well suited to purely axial tension or compression.  The classical arch shape of the compression reinforcing dramatically reduces the shear carried by the FRP webs.  Due to the low density of the FRP materials and the ability to place the compression reinforcing in-situ, what results is an economical structural member that can be used in the framing system of a bridge structure in the same manner as a steel or prestressed concrete beam, but that is much lighter and well suited to accelerated bridge construction and also provides for a potentially longer service life. 
 
 This project was a follow-on to a concept exploration project (HSR-23) that included the fabrication and laboratory testing of a beam prototype.  That project was sufficiently successful that this follow-on project was undertaken to build an 8-beam railroad bridge span and test it in the high-tonnage loop at the Association of American Railroads’ Transportation Technology Center in Pueblo, Colorado.  This project was jointly funded by NCHRP IDEA and High Speed Rail IDEA. 

The final report discusses laboratory test results and the performance of the bridge span at the Transportation Technology Center.HCB highway bridges have been constructed or are planned in Illinois, New Jersey, and Maine.   
 
 The final report for this IDEA project can be found at:
https://www.trb.org/studies/idea/finalreports/highspeedrail/hsr-43final_report.pdf