Anchor Bay Drive is a scenic road along Lake St. Clair in Clay, Michigan. This single entrance, dead-end road carries fishing boats and yachts to the lake access at the end of the road and provides access to the hundreds of homes that take advantage of the spectacular views of the lake and lagoon. Through inspection of the bridges that connect business and homes along Anchor Bay Drive to dry land, county engineers found all the bridges either structurally deficient or functionally obsolete; therefore, plans were put in place to have the bridges replaced.

The replacement of the Anchor Bay Drive Bridge presented multiple challenges to the county. The bridge needed to remain passable as it is the only point of access to the remainder of the road so a complete tear down and rebuild was not possible. Space around the bridge is extremely tight with houses packed in close to the bridge and very little dry land to maneuver on. This bridge is also just one of three that need replacement along Anchor Bay Drive so finding an economical option that could work for the additional bridges was a critical component of the decision. Based on previous experience, the St. Clair County crew contacted TEG Engineering to discuss the company’s patented galvanized cold formed steel tub girder bridge system: Con-Struct™.

The Con-Struct Bridge System proved to be an ideal choice for this project for numerous reasons. TEG Engineering worked closely with the county, fabricator, galvanizer and pre-caster to make slight design modifications to address the challenges of the bridge location. The original bridge abutments were in good shape and would not require replacement. Since the Con-Struct Bridge can be installed on top of existing substructures, this was another cost saving opportunity the county experienced. Timing was critical for this project so the galvanizer needed to be in contact with the fabricator to ensure a quick turn of the material upon receipt. A facility located on the same site as the galvanizer shaped and fabricated the tub girders for the new bridge, saving transportation cost and time. The 55-foot long girders were galvanized in a single dip and a thorough inspection ensured a quality coating was achieved. Once complete, the girders shipped to the job site for installation. 

One of the major advantages of this bridge system is the easy installation. The Con-Struct Bridge System can be delivered two ways; with the precast concrete deck attached to the tub girders or separate. For this project, they did NOT want the girders and deck to be attached due to the spacing at the installation site. The county demolished and installed the bridge one side at a time to ensure traffic flow could continue. The installation was much quicker than other available options due to its modular design and it allowed the crew to address other projects as needed at the same time with minimal impact. Both the tub girders and the decking take about half a day to set in place. The county’s own crew and equipment easily managed installation without additional equipment rentals or labor, saving the county even more time and money.

The Con-Struct Bridge system was developed in response to the Federal Highway Administration challenging bridge builders & specifiers to seek out economical bridge options that offer accelerated bridge construction and a longer expected life span, without compromising safety. With these goals in mind, the Con-Struct Bridge was created. Hot-dip galvanizing was selected due to its proven in-field performance, corrosion protection and longevity. The minimal maintenance required, compared to paint, offers another benefit for the bridge owner as well. Previous case studies have found the Con-Struct Bridge System installed in this manner to be 80% less expensive with 90% less traffic delays compared to typical DOT replacement options. 

With approximately 130,000 bridges rated structurally deficient or functionally obsolete in the United States, the demand for economical, long lasting bridge designs will continue to grow. According to the Short Span Steel Bridge Alliance, hot-dip galvanized bridges are approximately 25% more cost effective than concrete bridges. Hot-dip galvanizing is also beginning to make an impact in the bridge industry as a superior alternative to painting. Pair the state of the industry with engineers advocating for the use hot-dip galvanized steel in bridges; both the pie and slice of the pie are expected to grow for years to come.