DJ&A completed the design for the replacement of four log stringer bridges with permanent bridges near Edna Bay, a small rural community located on Kosciusko Island in Southwest Alaska. Access to this remote area was limited, and an initial site visit and site survey was completed by a two-person crew, who flew into the project site via float plane. DJ&A then analyzed and reviewed bridge and roadway alternatives, provided a hydraulic analysis, designed the re-alignment of the roadway approaches, and performed final structural design calculations for the bridge components.
Due to the remote location, all materials needed to be barged to the site. Such shipment is costly and restricts dimensions of materials. Two notable design approaches addressed this challenge:
- The design minimized the quantity of imported materials by calling for reinforced soil walls to decrease bridge span length.
- The design called for steel girder lengths that could readily be accommodated by available barges.
Key elements of the design included MSE wall abutments that allowed for shortening the bridge spans to fit the tight constraints of the roadway geometry while still meeting bankfull requirements. The designs also had to accommodate the restrictions associated with having to barge all materials to the remote site. This was accomplished by using steel girders designed with splices to keep individual members lengths to a minimum, and using glued-laminated deck panels that were light enough to be easily shipped and erected at the isolated location. The deck panels were also able to accommodate a crash-test rail system to meet the requirements of AASHTO LRFD Bridge Design Specifications.
- Conducted preliminary site visit and site survey
- Performed incidental realignment of up to 1000’ of existing roadway
- Designed bridge substructure elements
- Designed bridge approach guard rails and applicable signage
- Finalized design calculations and PS&E package
- Conducted bridge load rating calculations
- Prepared detailed project cost estimates
DJ&A incorporated a variety of solutions to aid in the constructability of this remote project, including the section of materials that were familiar to local contractors and that avoided the need for a crane being shipped to the project site.
The expertise of the personnel assigned to this project was exceptional. Construction challenges for the unique sites were identified early and remained a consideration throughout the design process. The consultant was always responsive in addressing our correspondence and our needs. They also added value by identifying logistical challenges that would likely arise during construction and proposing solutions. The project deliverable was timely and of high quality.