THE CONCRETE BRIDGE MAGAZINE

Spring 2019

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

Issue link: http://www.aspiremagazinebyengineers.com/i/1093138

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The Brotherhood Bridge (also known as the Mendenhall River Bridge) is located near Juneau, Alaska, about five miles downstream of the Mendenhall Glacier. The project, which has interesting historical connections to the region's Native Alaska community, faced several unique design challenges not often encountered outside of Alaska and incorporates many features commonly used by the Alaska Department of Transportation and Public Facilities (AKDOT&PF). History Five bridges have been built to cross the Mendenhall River at this location. The first road crossing at the river, a timber trestle, was constructed in 1903 for a total cost of $1700. The timber trestle was reconstructed in 1919 and then replaced with a single-lane, two-span steel truss in 1931. In 1965, the fourth bridge, a two-lane, three-span continuous steel girder structure, was built and named the "Brotherhood Bridge" to commemorate the 50th anniversary of the Alaska Native Brotherhood (ANB). Roy Peratrovich Jr. was an engineer for the Alaska Department of Highways t e a m t h a t d e s i g n e d t h e 1 9 6 5 structure. He is a Tlingit of the Raven Lukaax.ádi clan, the first Alaska Native person registered as a professional civil engineer in Alaska, and the son of prominent Alaska Native civil rights leaders Elizabeth and Roy Peratrovich Sr. In honor of the ANB anniversary, Peratrovich Jr. sculpted 10 bronze medallions with the ANB crest and imagery, which were incorporated into the bridge rail of the 1965 structure. The bridge served the community well for about five decades. But, as the weight of trucks increased, traffic d e m a n d s g re w, a n d d e s i g n c o d e requirements became more stringent, the need for a replacement bridge became apparent. Construction of the replacement bridge began in April 2014. The new bridge, which was rededicated in October 2015, retains the name and decorative bronze medallions that are a key part of the Brotherhood spirit. Geological and Hydrological Considerations The Mendenhall Glacier is viewed by more than 500,000 tourists every year. Currently, the face of the glacier is located about 1.5 miles from the Mendenhall Glacier Visitor Center; however, several hundred years ago, the face of the glacier was located near the bridge site. As the glacier has retreated, the surrounding ground surface has risen due to isostatic glacial rebound. At the bridge's location, the ground surface is rising at a rate of about 1 in. per year. Consequently, the river is incising and profile BROTHERHOOD BRIDGE (MENDENHALL RIVER BRIDGE) / JUNEAU, ALASKA BRIDGE DESIGN ENGINEER: Alaska Department of Transportation and Public Facilities Bridge Section, Juneau PRIME CONTRACTOR: Orion Marine Group, Anchorage, Alaska PRECASTER: Concrete Technology Corporation, Tacoma, Wash.—a PCI-certified producer GEOTECHNICAL AND FOUNDATION CONSULTANTS: Jacobs (formerly CH2M Hill), Bellevue, Wash. OTHER MATERIAL SUPPLIERS: Formliner (enlarged version of medallions): Spec Formliners Inc., Santa Ana, Calif.; elastomeric bearing pads: Seismic Energy Products LP, Athens, Tex. The Brotherhood Bridge over the Mendenhall River by Elmer Marx, Alaska Department of Transportation and Public Facilities Temporary work trestle. All Photos and Figures: Alaska Department of Transportation and Public Facilities. 20 | ASPIRE Spring 2019 P R O J E C T

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