Many state DOTs are collaborating with industry associations and experts to develop bridge beams that are more efficient for both bridge designers and precast producers. The widespread adoption of these new designs has given precast producers a competitive edge.
The Florida Department of Transportation (FDOT) worked in collaboration with the Florida Prestressed Concrete Association and Dr. Maher Tadros of the University of Nebraska to develop the Florida I-Beam (FIB). First produced by Standard Concrete Products in Tampa, in 2009, the beams feature a constant top and bottom flange with a variable web to facilitate the use of fillers in casting various beam sizes.
The FIB shape accommodates more strand than the old Florida Bulb-T beam design. The increased strand allows for longer beams, which means bridges can be designed with fewer beams and spans.
New FIBs have a wider bottom flange and lower center of gravity than the AASHTO beams, making them more stable in shipping, handling, and placement. The FIBs also have a fully predesigned reinforcement option that significantly reduces fabrication time.
In 2009, the Texas DOT (TxDOT) also replaced AASHTO Type 4 I-beams a new Texas I-Girder. The new beam features a thinner vertical section, thinner flange, and more bulbous bottom than the AASHTO design. Although it uses less material, the I-Girder is stronger so it can be designed in longer lengths, and bridges can be built with fewer beams.
The Precast Concrete Manufacturers’ Association of Texas (PCMA) consulted on the I-Girder design, with suggestions to make it easier for precasters to pour. Although its adoption meant precasters had to purchase new forms, the PCMA reports they have ultimately received more orders with the I-Girder — even with fewer beams being used per bridge.