A TEAM OF UP TO: 2 MAXIMUM TIME: 10 minutes

THE COMPETITION: IMPOUND: Yes (One Bridge & Log)

1) Materials:

a. The bridge is to be a single structure constructed of wood and bonded by glue~ No other materials shall be used. Particleboard, plywood, beaverboard, other composite wood products, bamboo or paper may not be used.

b. The entire bridge, including gussets, must be constructed of pieces of wood no larger than 1/4 inch high and ¼-in wide in cross-section. If dowels are used, they may not have a diameter greater than ¼ inch. There is no limit on the length of individual wood pieces used in the construction.

c. Any type of glue may be used.

2) Construction:

a. All construction must be completed prior to impoundment.

b. Any type of bridge that meets the specifications below may be constructed. Sound engineering and construction practices such as trusses, mitered joints/corners, gussets, and lamination (layers of wood glued together) are encouraged.

c. Unlimited lamination by the students is allowed; however, commercially laminated wood is not. Wood laminations may be any size provided the individual pieces used to make them comply with paragraph 1) c above.

d. The bridge must span an opening of 35.0 cm. There is no maximum length.

e. There is no maximum height.

f. The bridge must be at least 5.0 cm wide (outside dimension) along its entire span. The 5.0 cm width does not need to be at the same height all the way across the bridge.

g. No portion of the bridge may extend below the top surface of the test support prior to testing.

h. The bridge must accommodate a 5.0 cm long x 5.0 cm wide x 2.0 cm high loading block, a ¼-inch eyebolt centered on the block, a washer, and a wing nut centered at each of 3 possible load points and oriented so that the block’s 5.0 cm dimension is horizontal and at a right angle to the bridge span. All 3 load points will be on the centerline of the bridge, one at the center of the 35.0 cm opening between the test supports and the others 8.0 cm on either side of the center of the opening. Prior to the competition, teams must identify the load points by labeling them “A”, “B” and “C”, with the center load point labeled “B”. All teams will use the same load point that will not be announced until all bridges have been impounded.

i. The bottom surface of the loading block must be between 7.0 cm and 9.0 cm above the top surface of the test supports when placed on the load point.

j. Before it is impounded the bridge must marked in such a way that the event supervisor can easily identify to which team it belongs.

3) Testing:

a. All bridges and logs must be impounded before the start of the event and will be released from impound when the team has finished competing. No alterations to the bridge will be allowed once it has been impounded. Appeals by teams will not be processed after they remove their device from impound unless it has been released by the appeals committee.

b. Once teams enter the event area to compete, they may not leave the area or receive outside assistance, materials or communication until they are finished competing. Only contestants and judges will be allowed in the event area while teams are competing. Teams violating this rule will be disqualified.

c. All bridges will be assessed prior to testing to determine if they meet the specifications under Materials and Construction above.

d. The event supervisor will provide all equipment, except for eye protection, used for testing.

e. The students will center the bridge on the test supports that contain a 35.0 cm opening.

f. The students will place the loading block at the load point of the bridge. The students will insert the eyebolt through the bridge and loading block and secure it with a wing nut on top of the loading block. A 5-gallon plastic bucket (approximately 30-cm diameter) or other suitable container will be suspended from the eyebolt.

g. Students have a maximum of 10 minutes to add the sand. If the time expires, the bridge will be scored using the mass of the sand that has been loaded when the time expires.

h. The student will add sand to the bucket until failure occurs, or the maximum load of 15 kilograms is reached. Failure is defined as the inability of the bridge to carry additional load or when any part of the bridge extends more than 2.0-cm below the top of the test supports.

i. The mass of the loading block, eyebolt, washer, wing nut, bucket, and sand are included in the Load Supported. Event supervisors must verify that the combined mass they give each team is at least 15 kg prior to loading each bridge.

j. Sand added after failure will be removed by the event supervisor.

SCORING:

a. The Score will be determined by the Structural Efficiency equation:

Structural Efficiency = Load Supported (grams) I Mass of Bridge (grams)

b. Bridges that hold more than 15 kg will be scored using 15 kg as the Load Supported.

c. Bridges will be scored in 3 tiers. Bridges in the first 2 tiers will be ranked by their structural efficiency.

i) Bridges that meet all specifications under Materials and Construction will be ranked in the first tier.

ii) Bridges that DO NOT meet all of the specifications under Materials and Construction and can be tested will be ranked in the second tier.

iii) Bridges that cannot be tested for any reason (e.g., cannot accommodate the loading block or team does not have proper eye protection) will be ranked in the last tier by the bridge’s the bridge’s lighter mass.

d. Ties will be broken using the team’s log.

See 2006 Bridge Building Score Sheet