Context-Sensitive Bridge Design

This article describes the design and construction of a new bridge over the Cheboygan River in Michigan. The new bridge replaces a 40-year old prestressed concrete structure which had deteriorated severely due to the need for frequent use of de-icing salts. A context-sensitive design process was used. Several unusual challenges were encountered during design, including scheduling, permitting, constructability, and recreational requirements. In addition to the obvious requirement to carry vehicular traffic, pedestrians, snowmobiles, recreational boats, and utilities all had to be considered during the design and construction of the structure. Also, since Lincoln Avenue is a focal point of the area for entering tourists, aesthetics were important in reconstruction of the bridge. Installation time was also a major factor in structure selection, with several limitations imposed on the construction schedule and methods. After reviewing bridge options and considering the construction schedule required for each, a precast arch structure was selected primarily for functionality and aesthetics. Fabricating the precast members (arches, headwalls, and wingwalls) offsite while the contractor constructed the foundations saved a tremendous amount of time. Precasting the bridge members in the plant was a four-month process, and the contractor was able to set the precast members in six weeks. Engineers also designed a small drainage system to collect water and move it away from the precast concrete members. This drainage system, combined with the arch's natural ability to shed salt leachate, helps prevent damage from roadway salt and will allow the bridge to last its expected 75 to 100 years.