The Johnsburg Road bridge over Dutch Creek in McHenry County was rapidly failing, only 28 years into its intended 50-year lifespan. Chloride intrusion had corroded the prestressed steel strands within the bridge’s adjacent box beams, forcing four of the 13 beams out of service and restricting traffic. With the bridge continuing to deteriorate, McHenry County needed a replacement that could be completed in months instead of years.
Accelerating the project required working within significant constraints. To avoid lengthy environmental reviews, the replacement had to remain within the existing floodplain footprint, leaving the bridge abutments in place and limiting excavation. Because the existing abutments could not support additional loads, the replacement also needed to use adjacent box beams despite the shortcomings that had caused the original bridge to fail after just 28 years. The challenge became finding a way to improve the long-term performance of a bridge type already showing premature deterioration.
Stanley Consultants evaluated accelerated bridge construction techniques and investigated a recent Illinois pilot project that replaced traditional grouted joints with ultra-high-performance concrete (UHPC). Although the UHPC joints performed as intended, Stanley’s engineers determined they did not eliminate the deck cracking occurring above the beam joints. Through structural modeling and detailed analysis, the team identified transverse beam movement as the source of the cracking and developed a solution using carbon fiber-reinforced polymer wrap along the underside of the beams to limit joint separation. Additional design improvements sealed vulnerable beam ends from water and chloride intrusion, replaced rigid concrete pavement with a more flexible asphalt surface and eliminated deteriorating grout at the bearing pads.
The bridge reopened after just 32 days of construction, saving an estimated 18 months compared with the county’s original delivery approach while remaining under budget. Beyond accelerating delivery, the innovative rehabilitation strategy is expected to double the bridge’s service life for less than half the cost of a full bridge reconstruction, providing McHenry County with a faster, more economical approach that could help extend the life of similar bridges throughout Illinois.