NEWS from Southwest MS Resource Conservation & Development (RC&D), Inc.

PO Box 3670 Brookhaven, MS 39603-7670

601-833-5539 Fax 601-835-0054 E-mail southwest@msrcd.org

For more information contact Bennie Hutchins, RC&D Coordinator

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15TH NATIONAL TIMBER BRIDGE DESIGN COMPETITION

RESULTS ANNOUNCED

Twelve teams of students from universities across the US matched wits in the recently completed National Timber Bridge Design Competition. Open to student chapters of American Society of Civil Engineers (ASCE) and Forest Products Society (FPS), the competition was made possible by a grant from the US Forest Service through its Wood in Transportation Program. Additional financial support was provided by Unit Structures LLC. Southwest Mississippi Resource Conservation and Development (RC&D), Inc., coordinates the annual competition.

Each team designed, constructed and tested their bridges on their home campus, then submitted documentation of their activities and results to a panel of judges for review. The competition is conducted online via the Internet. Each team is required to post design drawings, test results, and project highlights on the web at www.msrcd.org.

Winner of the Best Overall Design Award was Oklahoma State University ASCE. Their design consisted of a plywood/fiberglass composite deck supported by a honeycomb grid sandwiched between compression and tension “skins”. This entry also placed first in Most Innovative Design and third in Best Support Structure. The team received cash awards totaling $1,050 for their efforts.

The highest money winner was the entry by the United States Military Academy, taking home $1,300 in prizes. Their entry took first place in Most Practical Design, first place in Best Support Structure and first place in Best Deck Design. Their entry consisted of a 2 x 12 lumber deck laid transversely over seven built-up I-beams, with the deck serving as the top flange of the I-beams and was built with only 1.4% (by weight) non-wood materials. All wood members were treated to ground-contact specifications using ACQ.

The other first-place winner was Team A from San Francisco State University ASCE, taking Most Aesthetic Design with its simple truss bridge using steel cables to support longitudinal beams and a transverse deck of treated hemlock fir. Another top performer was an entry from Oregon State University (Team 506), submitted by a joint effort of the ASCE and FPS students. The entry, using Copper Azole-treated Douglas Fir glue-laminated I-beams supporting a transverse deck, captured second place in three categories (Most Practical, Best Support Structure and Best Overall Design) and received awards totaling $900.

Swarthmore College (PA) ASCE, a first-time entry in the 2007 competition, placed second in Most Innovative Design and third in Best Overall Design with its design using three support girders incorporating a reverse king-post with ½-inch tension cables supporting a rod-stressed laminated deck of ACQ-treated southern yellow pine.

Additional entries in the 2007 Competition included teams from Clarkson University, Ohio State University, University of Missouri-Columbia, Oregon State University (Team B), University of Tennessee at Martin, San Francisco State University (Team B), and University of Arkansas at Little Rock (FPS).

For a complete review of 2007 Competition Results and each individual entry including drawings and photos, go to www.msrcd.org/bridge.htm and select from menu. Results of 1998-2006 competitions are also posted online. Rules for the 2008 competition will be similar to 2006 Rules that are already posted online. For final 2008 Rules or additional information contact Southwest Mississippi RC&D, Inc., competition coordinator, at southwest@msrcd.org.

The test bridges were 12.5 feet (3.8 m) long and 55 inches (1.4 m) wide and were loaded with a test weight of approximately 4,500 pounds. Average weight of the bridge models was 984 pounds (447 kg). At full loading, maximum bridge deflection ranged from 1.78 mm to 8.67 mm. Maximum allowable deflection was 9.5 mm. Percent non-wood materials in the bridges averaged 7%; maximum percent non-wood materials allowed was 25 percent, by weight.

The competition's objectives are to promote interest in the use of wood as a competitive bridge construction material, to generate innovative and cost-effective timber bridge design techniques, and to develop an appreciation of the engineering capabilities of wood among future transportation and forest products engineers. Following the competition, most of the bridges were placed into use as trail bridges.

Judges for the competition were Scott Groenier, P.E., Missoula (MT) Technology and Development Center, USDA-Forest Service, and Paul Gilham, P.E., Western Wood Structures, Inc., Tualatin, Oregon.