Click name to view biography.


Jason Fullerton (Team Leader)

Sara Lynn Baumann

Soong Ching Liw

John Rejebian

Project Background


Northern Arizona University in Flagstaff, AZ is currently involved in a cooperative project with the College of Arts and Letters to construct an authentic Japanese garden.  The garden is located in a forested area adjacent to the southwest corner of the NAU Ceramics building.  At present, the garden consists of a traditional Japanese teahouse and limited trail system; however, plans for further development include a Japanese style earthen bridge, an elaborate trail system, and Japanese style sculptures and landscaping throughout the garden.

Presently, the project is focused on the design and analysis of a Japanese earthen bridge, more traditionally known as a do bashi.  The do bashi style bridge is typically made from circular wood timbers and incorporates an “earthen overlay,” which blends the trail into the bridge creating a natural transition.  Another traditional aspect of a do bashi is its arched superstructure, which, given the framework of the project, will span approximately 40-ft across a small wash in the garden area producing a rise of nearly 5-ft at the crown of the arch.  In addition to being structurally sound and complying with the code/permitting requirements of the International Building Code (IBC) and the National Design Specification for Wood Construction (NDS), the bridge must also be aesthetically pleasing and adhere to traditional Japanese styling.




To design and analyze a Japanese earthen bridge, or a do bashi.


The challenges of designing a traditional Japanese earthen bridge arise in the need for the bridge to retain its historical authenticity, while still remaining structurally sound and compliant with current building regulations.  Among the most difficult design challenges was the addition of a handrail to the bridge to comply with OSHA regulations, as well as the major differences found in material availability, constructability the use of traditional methods, and the vast differences in environmental conditions between Japan and Flagstaff, AZ.


Using conceptual drawings created by Japanese landscape architects who have visited the site and Allowable Stress Design (ASD), the current practice for wood design, a modern do bashi was developed for the NAU campus.  The structure is designed to withstand all required loads set forth by the International Building Code (IBC) and the City of Flagstaff.  All analysis and load combinations are based on ASD methods and allowable design values taken from the National Design Specification of Wood Products (NDS).  Working closely with several academic advisors and industry professionals, a uniquely authentic design was developed for the project.  All funding for this project design was provided by The Department of Civil and Environmental Engineering at Northern Arizona University.








Saturday, February 24, 2007:

Today, the team met in the NAU Ceramics Building with Doug Macy, the architect behind the project, to discuss our ideas for design and construction.


Click photos to enlarge.




Viewing the plans






AutoCAD was the primary software used throughout the project.  It helped greatly by providing a visual for conceptual planning as well as creating details for construction.




Bridge Design Details
using AutoCAD




Handrail Details




Bent Details





Girder and Column Connections



Special Thanks to:

Dr. Joshua Hewes, Dr. Debra Larson, Dr. Clyde Holland, John Tingerthal, Dr. Eugene Loverich, Jason Hess, Josh Spear, and Doug Macy.


American Wood Council. National Design Specification for Wood Construction, 2001 Edition, American Forest and Paper Association Inc, 2001

ASCE Standard, Minimum Design Loads for Buildings and other Structures, American Society of Civil Engineers, 2003.

Beer, Ferdinand P. Mechanics of Materials, 3rd Edition, McGraw Hill Inc, 2002.

Breyer E. Donald. Design of Wood Structures-ASD, 5th Edition, McGraw Hill Inc, 2003

Coduto, Donald P. Geotechnical Engineering, Prentice Hall Inc, 1999

International Building Code, 2006 Edition, International Code Council, 2006.

McCormac, Jack C. and Nelson, James K. Design of Reinforced Concrete, 7th Edition, John Wiley and Sons Inc, 2006

Nelson, James K. Structural Analysis Using Classical and Matrix Methods, 3rd Edition, John Wiley and Sons Inc, 2003