Saginaw County Rebuilds Two Bridges
Two bridges receive complete remodels to provide safer transportation
SAGINAW COUNTY – Two bridges 6.7 miles apart near the Village of St. Charles recently underwent construction to be rehabilitated. The first bridge is located on Hemlock Road over the South Branch of the Bad River and the second is on Fordney Road over Beaver Creek. Both roads provide essential access for residences and fire/safety and keeping these open is a priority.
Spicer Group is responsible for conducting bridge safety inspections for bridges located within Saginaw County and has been completing these inspections since the 1990s. As noted during the routine inspections, it was observed these bridges had significant deterioration from deck leakage, age, and general wear. This deterioration led to deck spalling and severe section loss with holes in the beam ends. This caused both bridges to be posted at a reduced weight limit, restricting truck traffic over the bridges.
Based on the inspections and repair recommendations, the Saginaw County Road Commission (SCRC) agreed that the best option was to replace both superstructures. Both of these structures are listed in the National Bridge inventory and are eligible for federal funding through the Michigan Department of Transportation’s (MDOT) Local Agency Program (LAP). The SCRC submitted applications for both structures in 2020 and 2021. The Hemlock Rd. and Fordney Rd. Bridge projects were each awarded $800,000 in funds from this program towards superstructure replacements.
The superstructure of a bridge supports and stabilizes the deck, transferring the weight of traffic to the substructures. The substructure of a bridge—better known as the foundation— supports the loads from the deck and superstructure. Because the foundation of these structures was in relatively good condition, the most economical solution was to replace the superstructure.
The design of the projects began in early 2022 for each bridge. The existing structures were surveyed and evaluated for environmental impacts, soil conditions, hydraulics, traffic, and utilities, and then preliminary plans were prepared. The existing Hemlock and Fordney Road Bridges had similar span and substructure configurations which resulted in similar superstructure designs, saving both time and money on the projects.
During the preliminary design phase, Spicer Group presented several options to the SCRC for replacing the superstructures. The options included Steel I-Beams, Prestressed Concrete I-Beams, and Prestressed Concrete Box Beams. Due to high construction prices following the Covid-19 pandemic and long lead times on conventional materials, the SCRC was looking for ways to reduce costs and avoid delays in the construction of these bridges.
“The answer came to us at a bridge conference in March 2022, where one of the presenters was speaking on press brake tub girders.” Dan Zeddies P.E., Project Manager from Spicer Group said. “Press brake tub girders (PBTG) are folded plates made of galvanized steel plates, shallow, trapezoid-shaped boxes. They are a newer and economic alternative being used in bridge construction.”
These PBTG superstructures had also been utilized recently in the Michigan Bridge Bundling project that replaced 19 bridge superstructures throughout the state. After the conference, Spicer Group’s engineers did their research, comparing the PBTGs to the other options originally proposed. This superstructure type met the design parameters for cost and efficiency. With SCRC’s support, the PBTGs were the selected solution and were included in the final drawings.
“These press brake tub girders saved on costs and time significantly.” Zeddies said “They are galvanized to prevent corrosion, designed by the manufacturer, and are less maintenance because they don’t
require painting.”
Spicer Group coordinated with the manufacturer throughout the PBTG design process, utilizing Bentley’s OpenBridge Designer for analysis of the superstructure, substructure, deck, and bridge geometry. The manufacturer was able to complete the final designs and send the PBTGs out for production.
The projects were both bid together, and demolition of both existing structures began in early summer of 2023 with construction beginning immediately after. The Hemlock Road Bridge was opened to traffic on September 1st and the Fordney Road Bridge was close to opening at the time of publication.
