Experimental Evaluation of a New Double Composite System for Steel Bridges

Steel bridges are constructed using steel sections that consist of either rolled wide flanges or builtup girders. Built-up girders, also known as plate girders, are made up of flanges, webs and stiffeners, which are typically welded together. The problem with plate girders is that long-term fatigue crack initiation can manifest at the welded details. Moreover, the webs are relatively thin, which require the addition of transverse stiffeners to achieve the required shear capacity. The thin webs can also corrode through fairly quickly once corrosion begins. From a maintenance perspective, the added stiffeners to enhance the shear capacity can trap debris and moisture on the bottom flange. This can give rise to corrosion fatigue, which is not addressed in the American Association of State Highway and Transportation Officials (AASHTO) Design Specifications. On the other hand, the use of rolled beams in steel bridges can be very advantageous since the webs are an integral part of the flanges in that the beams are rolled out of one piece of steel and the webs are significantly thicker than built-up girder webs. Therefore, there is no need for transverse stiffeners to enhance the shear capacity of the web. From a maintenance and deterioration perspective, the beams have smoother lines with no stiffeners to trap moisture and debris on the bottom flange. Despite their advantage, rolled beams are limited in sizes, which impose constraint on their use to relatively short spans due to deflection requirements. The newly proposed superstructure utilizes rolled beams in combination with a reinforced concrete slab, resting on the bottom flanges of the beams, to enhance the deflection of the system and allow for longer spans to be built using rolled beams. The added slab increases the cross-sectional moment of inertia; thereby lowering the deflection of the whole system. The bottom slab also significantly enhances the torsional stability of the bridge as the geometry of the bridge is transformed to a closed-section. The enhanced torsional stability eliminates the need for crossbracing or lateral bracings, which eradicates potential problems associated with distortion fatigue at the web gab of connection plates. In addition, the new system will employ the concept of Simple Made Continuous (SMC) where the connection of the spans over the pier are “simple for dead – continuous for live” or SD-CL. Typically, continuous bridges are more economical than simple span bridges because they develop smaller positive interior span moments due to the negative moments at the continuous ends.


  • English


  • Status: Active
  • Funding: $170000
  • Contract Numbers:


  • Sponsor Organizations:

    Research and Innovative Technology Administration

    University Transportation Centers Program
    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Managing Organizations:

    Mountain-Plains Consortium

    North Dakota State University
    Fargo, ND  United States  58108
  • Project Managers:

    Tolliver, Denver

  • Performing Organizations:

    Dept. of Civil and Environmental Engineering

    Colorado State University
    Fort Collins, CO  United States 
  • Principal Investigators:

    Mahmoud, Hussam

  • Start Date: 20160329
  • Expected Completion Date: 20190930
  • Actual Completion Date: 0
  • USDOT Program: University Transportation Centers Program
  • Source Data: MPC-508

Subject/Index Terms

Filing Info

  • Accession Number: 01601184
  • Record Type: Research project
  • Source Agency: Mountain-Plains Consortium
  • Contract Numbers: DTRT13-G-UTC38
  • Files: UTC, RIP
  • Created Date: May 31 2016 4:38PM