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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11TH NATIONAL TIMBER BRIDGE DESIGN COMPETITION

RESULTS ANNOUNCED

Five 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 United States Military Academy ASCE. Their design consisted of 5 LVL (laminated veneer lumber)

I-beams with top flanges of 2" x 12" CCA-treated Southern Yellow Pine (SYP) that formed a continuous "subdeck" supporting a transverse deck of 2" x 8" SYP with ship-lap joints screwed together and into the compressive flange of the I-beam supports. This entry also placed first in Best Deck Design and Most Practical Design, and second in Most Innovative and Best Support Structure. The team received cash awards totaling $3,850 for their efforts.

The second place money winner was Oregon State University ASCE with awards totaling $2,550. Their entry placed first in Most Aesthetic Design, second in both Best Overall Design and Most Practical, third in Most Innovative, and Best Support Structure. Their design featured a deck of 2x6 Douglas Fir placed longitudinally over 12 engineered I-joist transverse floor beams supported by 2 outside parallel-chord trusses incorporating a tension rod suspension of "M" configuration.

Another first place winner was the entry of the Washington University at St. Louis ASCE team, capturing first place in Best Support Structure for their fabricated I-beams that incorporated the top flange of 2" x 8" SYP into a longitudinal deck with load transferred by 1" x 4" transverse purlins acting as floor beams. The four I-beams used a web of 3/4-inch plywood. This light-weight bridge also was awarded third place in both Best Overall Design and Most Practical Design. Awards totaled $1,700.

The final first place award was for Most Innovative Design awarded to the entry of Virginia Tech's FPS chapter. The team used CCA-treated SYP recycled from residential exterior decks to construct the 2 outside arch supports incorporating six 1/4" steel suspension cables per arch. The arches were constructed of 2" x 6" x 14" CCA SYP glued with Resorcinol Resin using an experimental coupling agent, hydroxymethylresorcinol (HMR). The deck was composed of carbon fiber sheets sandwiched between 1/4 inch plywood and 1" x 6" SYP. The 5 longitudinal I-joists were treated with ACQ (Ammonical Copper Quat). The VT entry also placed second in Best Deck Design and third in Most Aesthetic, receiving $1,200 in awards.

The Ohio State University ASCE team received $600 for their second place finish as Most Aesthetic and third place in Best Deck Design. Their entry featured 2 LVL box beams supporting a 3-layered deck of 5/4-inch SYP.

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 909 pounds (412 kg). At full loading, maximum bridge deflection ranged from 2.66mm to 6.05mm. Maximum allowable deflection was 9.5 mm. Percent non-wood materials in the bridges averaged 3.7%; maximum percent non-wood materials allowed was 25 percent, by weight.

For a complete review of 2003 Competition Results and each individual entry including drawings and photos, go to www.msrcd.org/bridge.htm and select from menu. Results of 1998-2002 competitions are also posted online. Rules for the 2004 competition will be posted online by mid-August 2003. For additional information contact Southwest Mississippi RC&D, Inc., competition coordinator at southwest@msrcd.org.

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.