How Eight Mile Road Bridge in Hamilton County, Ohio, used a

bridge system prefabricated with integral beams and deck

incorporating the entire superstructure for a rapid installation.

Article contributed by Composite Advantage

Eight Mile Road Bridge, a short span concrete structure built in 1940, needed to be replaced in Hamilton County, near Cincinnati, Ohio.

In addition to replacing the bridge deck slab, the abutments required rehabilitation to extend the life of the structure. In 2000 and 2001, Hamilton County engineers chose to rehabilitate three bridges on Five Mile Road (Bridges B-0071, B-0087, and B-0171) with Fiber Reinforced Polymer (FRP) bridge decks on pre-cast, pre-stressed concrete beams.

Eight Mile Road was the first site in the United States to use a Fiber Reinforced Polymer (FRP) composite superstructure, that also integrates a drop-in-place technology.

An inspection conducted in July 2008 revealed only minor surface cracking in the decks. The decks were cleaned and sealed. Testing confirmed deck deflection was unaffected and corrosion nonexistent.

For Hamilton County engineers, the positive performance of the Five Mile Road composite bridge decks has established a track record for the technology’s capability to reduce maintenance and extend service life through the non-corrosive nature of the material. Innovative Bridge Research and Construction (IBRC) program funding supported the county’s request to use composite technology for Eight Mile Road. But county engineers had a more aggressive goal for the aging bridge.

The county’s bridge department wanted to eliminate the horizontal construction joints used in the previous composite deck designs. And, instead of a product that just provided a composite deck on reinforced concrete beams, engineers were looking for a total bridge superstructure application.

A unique infusion process was used to mold eight panels that covered the bridge’s full span length (22 feet) and were less than 8 feet wide. Panel width was dictated by shipping size. A joint beam was bonded and bolted to join adjacent panels.

That’s where the integrated SuperFiberSPAN FRP bridge system came in. Unlike conventional FRP decks on steel beams, the bridge system is prefabricated with integral beams and deck incorporating the entire superstructure. Panels can be dropped in place for rapid installation.

“Eight Mile Road was the first site in the United States to receive this integrated composite superstructure” said Steve Mary, an engineer for Hamilton County, Ohio. “Typically, failure or structural issues occur where materials are joined together. This system eliminates the connection joints between deck and beams. Our office has always had a special interest in using innovative materials and products because our objective is to continually improve our infrastructure and extend service life. This integrated composite bridge system was a logical next step.”

Bridge parameters called for a 22 foot span and a width of 62 feet (1,364 square feet). Other specifications included the standard AASHTO HS 20 loading, an alternate military truck loading; L/800 deflection criteria; an integral concrete diaphragm; skew, cross-slope kick across the bridge to control asphalt thickness and an asphalt wearing surface. CA designed the FRP bridge superstructure, while LJB Engineering designed the concrete approaches leading up to the bridge’s entrance.

A unique infusion process was used to mold eight panels that covered the bridge’s full span length (22 feet) and were just less than 8 feet wide. Panel width was dictated by shipping size. A joint beam was bonded and bolted to join adjacent panels. The bridge skew was molded into the ends of net-shape panels. Beams and deck were integrally molded together. The deck facings, beam shear webs and beam caps consisted of multi-axial fiberglass fabrics.

Eight Mile’s short span and low traffic volume made the bridge a good candidate for this new system,” said Steve Mary, an engineer for Hamilton County, Ohio, who worked on the Eight Mile Bridge project. “Traffic downtime was close to 100 days with weather a partial contributor. But it only took one day to install the Fiber Reinforced Polymer bridge deck panels.

In order to handle the high shear loads and crushing loads on the deck, a fiber reinforced internal core was used. The core has multiple shear webs in both longitudinal and transverse directions to minimize deck deflection. The entire lay-up of beams and deck were infused with a corrosion resistant vinyl ester resin with pigment and UV inhibitor. Eight panels were molded to cover the width of the bridge. A structural test program was conducted to validate the design.