Mars Hill/Lowell Observatory Truss Bridge
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Project Background
Purpose of the Project
Lowell Observatory has future plans to develop a large piece of land located on
Mars Hill in Flagstaff, AZ.
The area
that is targeted for the future development is located across a ravine to the
south of the lookout on Mars Hill Road.
A bridge spanning the ravine will improve traffic flow and access to this
area.
This project will provide the
Observatory with a 60% design of the bridge and a model to aid in securing funds
for the further design and construction.
Bridge Design
The project stakeholders have requested the design model that of a Town Lattice
Truss. The bridge will span 120 feet, without any bents.
The bridge itself is design to be 128 feet in length (longer than the
span to allow for bearings and expansion connections) and 18 feet wide in
between the lattice trusses.
The
trusses will be approximately 16 feet in height and the roof will have slope of
20 degrees.
Materials
The project stakeholders desired the bridge to be constructed out
of local materials and if possible utilize Ponderosa Pine found on the property.
After researching the strength of wooden materials and the requirements
of timber that is used for structural purposes, the recommendation was made to
purchase timber from a mill to meet all of the requirements and assure the
quality of the materials.
In
addition to this, Ponderosa Engineering also recommended the use of Douglas Fir
rather than Ponderosa Pine, as the primary construction material.
However, to meet the client’s desires, Ponderosa Pine from the Lowell
property will be cut and used as outer sheathing for the covered bridge.
This will include any usable wood cut while clearing the project site.
The project stakeholders have also requested the roof of the
structure match the metal roofing that is common throughout the Lowell
Observatory Property.
This request
will be met in the design as much as possible.