Covered bridges usually seem like historical relics, or the subjects of romantic novels. However, an Ohio county is in the process of building several new covered bridges because of their appearance, durability, low maintenance and competitive cost.
Ashtabula County, Ohio, engineer John Smolen says that covered bridges not only recall the best of the past, but have significant value for the future. The county has 12 covered bridges that date back to 1868, and Smolen says, "The timber bridges have actually shown less deterioration than steel and concrete bridges over the past 130 years, so we asked ourselves the question, why not continue to build them?" The county recently completed a timber-covered bridge across Mill Creek in Jefferson Township. It is 107 ft long and 22 ft wide. The bridge will be known as the Giddings Road Covered Bridge. It is a Pratt arch design, which has two huge 48,000-lb glued laminated timber trusses as its main side supports.
The design
Designed by Smolen and fabricated by Sentinel Structures Inc. of Peshtigo, Wis., it was shipped, knocked down, and reassembled at the job site. A special section of the federal highway bill, which allocated money for timber structures, was tapped for the project.
Smolen says covered timber bridges have the advantages of being lighter-weight than steel, cost competitive with other materials, and are not subject to rusting or corrosion from road salt.
"We like the lower maintenance costs of the timber covered bridges, and the public likes their old-fashioned, nostalgic look," Smolen adds. The county has plans for three more new covered bridges.
The Southern Pine trusses for the Giddings Road Bridge are 117 ft long and 14 ft 3 1/8 in. high. They have triple glued laminated top and bottom chords. Top chords measure 5 1/8 in. x 12 3/8 in. and bottom chords measure 6 3/4 in. x 16 1/2 in.
Bottom chords and 8 1/2-ft x 26 1/8-in. floor beams are treated with creosote. The vertical webs in the truss are 6 3/4 in. x 12 3/8 in. or 5 1/8 in. x 11 in. spaced 8 ft 8 in. apart, with diagonals being steel tension members. The bridge decking is 6-in. x 8-in. Red Oak timbers and creosote treated. All other wood is untreated Southern Pine or White Oak.
