6/4/2025 McCall Macomber
Written by McCall Macomber
Bridges with precast and prestressed concrete deck beams, which are stressed during production to strengthen them against forces experienced while in use, account for nearly 35% of all bridges in Illinois, according to the National Bridge Inventory.
But when PPC deck beams develop cracks from loads heavier than they were designed to carry, it becomes difficult for engineers to determine how much load the damaged beams can still support safely.
Illinois Center for Transportation and Illinois Department of Transportation seek a solution in the joint project, R27-226: Residual Capacity of Precast Prestressed Concrete Deck Beams with Transverse Cracks.
Bassem Andrawes, University of Illinois Urbana-Champaign professor, and Robert Perkins, IDOT’s local bridge unit chief, aimed to quantify the impacts of transverse, or perpendicular, cracks on PPC deck beams, the effects of which have not been well studied.
To assess transverse cracks’ effects, Andrawes’ team conducted lab tests with full-scale beams as well as modeling simulations to determine the effects of variables such as materials and beam geometry.
They tested two PPC deck beams with transverse cracks that had previously been in use to determine their ability to bear loads, stresses and flexural behavior, or resistance to bending.
They also developed a finite element model of one beam to determine the built-up stresses and assess its capacity with transverse cracks compared to when it was built.
Findings revealed the remaining load-bearing capacity is dependent on whether there are circular or rectangular voids in the beam design and severity of cracking.
IDOT will use the findings to develop guidelines for determining the remaining capacity of PPC deck beams with transverse cracks.
Accurately load rating PPC deck beams with transverse cracks will assist IDOT with making decisions on whether to open a bridge to traffic or restrict its weight limit.
“This research will help IDOT determine any necessary load restrictions that may be required when transverse cracks are found on PPC deck beams, protecting the travelling public,” Perkins said.