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 F. Hutchins, RC&D Coordinator

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13TH 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 the Southern Pine Council of the Southern Forest Products Association, Unit Structures LLC, Wood Protection Products, Inc., and Weyerhaeuser Company. 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 sponsored by Weyerhaeuser Company was San Francisco State University ASCE. Their design consisted of transverse deck floor beams and stringers of Northern Douglas Fir supported by two clear-heart California Redwood laminated arches and a suspension system of 5/8-inch steel rods and ¼-inch steel cables. Their goal of designing a structure for both strength and beauty was also rewarded with the first place award for Most Aesthetic. This entry also placed first in Best Support Structure and Best Deck, judged by performance (deflection), weight, percent nonwood, practicality, innovation and aesthetics. The team received cash awards totaling $1,700 for their efforts, making it the top money-winner.

The second highest money winner was University of Texas at San Antonio ASCE, taking home $1,200 in prizes. Their entry did not win a first place award, but was a consistent performer, placing second in Best Overall Design, Best Support Structure, Most Innovative Design and Most Aesthetic. The two “half-through” tapered arches were designed on catenary curves and consisted of built-up I-shaped cross sections. A suspension system of six 5/6-inch steel rods supported stringers, floor beams, and a transverse deck of 2-inch by 4-inch ship-lap members. All wood members were treated to AWPA standards with chromated copper arsenate (CCA).

Other first-place winners were United States Military Academy ASCE for Best Deck Design, University of Arkansas at Little Rock FPS for Most Practical Design and Clarkson University ASCE for Most Innovative Design. Other entries in the 2005 Competition were University of Wisconsin at Platteville ASCE, University of Missouri at Columbia ASCE, Ohio State University ASCE, Oregon State University ASCE/FPS, Washington University at St. Louis ASCE, Virginia Tech FPS and a second entry from San Francisco State University ASCE (truss design).

For a complete review of 2005 Competition Results and each individual entry including drawings and photos, go to www.msrcd.org/bridge.htm and select from menu. Results of 1998-2004 competitions are also posted online. Rules for the 2006 competition will be similar to 2004 Rules that are already posted online. For final 2006 Rules or additional information contact Southwest Mississippi RC&D, Inc., competition coordinator, at southwest@msrcd.org.

The test bridges were 12.5 feet (3.8m) long and 4.6 feet (1.4m) wide and were loaded with a test weight of approximately 4,500 pounds. Average weight of the bridge models was 920 pounds (418 kg). At full loading, maximum bridge deflection ranged from 1.14mm to 8.93mm. Maximum allowable deflection was 9.5mm. Percent non-wood materials in the bridges averaged 7.3%; 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 Technology and Development Center, USDA-Forest Service, and Paul Gilham, P.E., Western Wood Structures, Inc., Tualatin, Oregon.