Date of Award

6-10-2014

Document Type

Thesis - SCU Access Only

Publisher

Santa Clara University

Department

Civil Engineering

First Advisor

Tracy Abbott

Abstract

A pedestrian bridge was designed for the 22nd National Timber Bridge Design Competition. The competition is sponsored by the Mississippi Research Council and Development and open to all student chapters of the American Society of Engineers and Forest Product Society. Entry to this competition was a first in Santa Clara University history. The design process included meeting the competition loading of 4500 pounds as well as the 150 psf requirement outlined in the American Association State Highway Transportation Officials Guide to Pedestrian Bridge Design. The deflection limits for the competition were L/100 for the deck span (0.105”) and L/400 for the bridge span (0.420”). In addition, all dimension restrictions for the competition were considered for all alternatives considered. A detailed evaluation of three alternatives was conducted to choose the best alternative: simple beam bridge, Gambrel truss bridge, and a Pratt truss bridge. The final design selected for construction was the Pratt truss bridge that used redwood and Douglas Fir Larch for all members. The bridge performed slightly different than expected when loaded with 4500lbs; a deflection of 0.45” versus the 0.42” allowable was observed. Despite exceeding the allowable deflection by 0.03” the team was able to place in two of the six categories, second place in best deck design and most practical design. The bridge is being transported to a local farm in Watsonville, California where it will be used by a farmer to cross a ravine.

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