- Two research projects looked at how to develop economical alternatives for longer-span bridges and investigate a new bridge system for short-span bridges
- The research helped to further the potential for precast, prestressed concrete bridge systems
The state of Texas has more bridges than any other state in the nation, with over 50,000 total. Maintaining structurally sound, shorter- and longer-span bridges was the driving force in two collaborative projects recently completed by Dr. Mary Beth Hueste, a Zachry Department of Civil Engineering professor at Texas A&M and Texas A&M Transportation Institute (TTI) research engineer, and the Texas Department of Transportation (TxDOT).
Hueste is dedicated to furthering the understanding of the use of new materials and designs for bridge structures, with a focus on prestressed concrete bridge systems. Prestressed members are put into a state of compression using high-strength steel tendons before external loads are applied.
“The use of precast, prestressed concrete bridge girders in Texas and other parts of the U.S. has proven to provide economical bridge systems that have a number of benefits,” Hueste said. “Producing the girders at the precast plant leads to enhanced quality because there is more control of the materials and the manufacturing process at the plant during fabrication. By investigating new bridge systems that utilize precast girders, TxDOT and other bridge owners have additional options for bridge designs that can be selected when the site conditions or other factors make precast concrete the optimal alternative.”
Continuous prestressed concrete girder bridges
The first project centered on continuous prestressed concrete girder bridges. Most Texas bridge structures are constructed with precast concrete girders with a cast-in-place concrete bridge deck. The bridge girders are fabricated at a precast plant where they are prestressed to avoid cracking of the concrete and to achieve longer span lengths compared to conventional reinforced concrete bridges. However, the precast girder units are limited to 160 feet due to weight and length restrictions on transporting them from the plant to the bridge site. This project’s primary focus was to develop innovative and economical alternatives for longer-span bridges, with main spans up to 300 feet.
Hueste was the research supervisor on this project. She worked alongside Dr. John Mander, Zachry professor in design and construction integration and TTI research engineer, and Reza Baie, Anagha Parkar, Akshay Parchure, Jennifer Prouty and Tristan Sarremejane, civil engineering graduate students employed by TTI.
Hueste and her team of researchers found that with in-span spliced girder technology and continuous prestressing installed at the bridge site, the span length of precast concrete girder bridges can be nearly doubled. In-span splicing involves connecting the precast girder sections at optimal locations within the span such that the overall span length between bridge supports is greater than the length of the individual girder segments.