Student Members: Nicholas Schwantes
Faculty Advisors: Dr. Scott Hamel
Abstract:
The Iditarod National Historic Trail is a recreational trail system that follows antiquated transport
routes across the coast and through the interior of Alaska. This trail is unimproved in certain
areas and crosses many waterways, including rivers and creeks. Since this trail is commonly used
for hiking and backpacking, efforts have been undertaken to make water crossings safer and
easier, particularly in the section that crosses the Kenai peninsula.
This study examines the feasibility of constructing a bridge over the Bertha Creek Iditarod Trail
Crossing in Turnagain Pass. In this report, we prepare a 65% design of a pony truss bridge and a
10% design of a through truss bridge, including supporting calculations and construction
drawings. Various types of structural modeling and analysis software are used to analyze the
bridge alternatives. We compare and contrast these designs on multiple different metrics –
primarily constructability, cost, and aesthetics.
The results indicate that, although a pony truss bridge would be more expensive to construct, it
would be much easier to construct, could be almost entirely shop fabricated, and would better
suit the intended usage of the trail system. Both bridge designs would require a helicopter,
although the pony truss would take less time to construct, due to less welding and shoring
activities being required on-site. Considering the benefits of each alternative leads to the
conclusion that a pony truss bridge is preferred over the construction of a through truss bridge at
this location.
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