2010 International Bridge Building Contest Rules

In order to receive official wood and participate in this contest, a High School student must have placed first or second in a Regional Contest and be reported, by the Regional Coordinator, to Robert Malkovsky by phone: (610) 627-6381, fax: (610) 891-0898, or e-mail: rmalkovs@rtmsd.org. Students may participate in person, by proxy or by mail entry.

The object of this contest is to see who can design, construct and test the most efficient bridge within the specifications. Model bridges are intended to be simplified versions of real-world bridges, which are designed to accept a load in any position and permit the load to travel across the entire bridge.

1. The bridge must be constructed only from the official 3/32-inch square cross-section basswood included in the kit and any commonly available adhesive.
2. The official basswood may be notched, cut, sanded or laminated in any manner but must still be identifiable as the original official basswood.
3. No other materials may be used. The bridge may not be stained, painted or coated in any fashion with any foreign substance.

1. The bridge mass shall be no greater than 30.00 grams.
2. The bridge (see Figure 1) must span a gap (S) of 300. mm, be no longer (L) than 400. mm, be no taller (H) than 180. mm above the support surfaces, and have a maximum width (W) of 70. mm. It must have a horizontal loading plane that is a maximum height (P) of 80. mm above the support surfaces.
3. The bridge structure may not project below the support surfaces. A bridge that deflects or partially fails such that a portion of the bridge projects below the support surfaces and engages the vertical front surface of the supporting structure will be disqualified.
4. The bridge must be constructed to provide a horizontal support surface for the loading plate and rod at each of the three possible loading positions. These three positions, at the mid-span of the bridge and 60. mm to either side of the center, will be clearly and consecutively labeled "1, 2, 3" from either end of the bridge by the participant before submission to the judges (see 3b). The horizontal loading plane must be a minimum length (R) of 160. mm and centered on the mid-span of the bridge. The bridge structure must allow the loading rod (see 3a) to be mounted from below.
5. The bridge must have a minimum clearance (C) of 60. mm in height above the support surfaces. This clearance also extends 80. mm toward either end of the bridge from the center point of the bridge. It coincides with the horizontal loading plane, and lies directly beneath it. No part of the bridge structure may be built around this clearance area, and a 60. mm high, by 160. mm wide block must pass cleanly under the bridge.

1. The load will be applied by means of a 40. mm square plate that is 19.05 mm (3/4 inch) in thickness. A 9.53 mm (3/8 inch) diameter loading rod is attached from below to the center of the plate (see Figure 2). The plate will be horizontal, it will not pivot on the loading rod, and the sides of the plate will be parallel to the longitudinal axis of the bridge.
2. The three loading positions will be located on the horizontal loading plane. The center loading position (numbered "2") will be located at the center point of the bridge. The other two loading positions (numbered "1" and "3") will be located 60. mm toward either end of the bridge from the center.
3. On the day of the competition, the judges will randomly draw the number of the loading position to be used; it will be the same for all bridges tested.

1. On the day of the contest, participants will center their bridge on the loading surfaces. They will have previously located the loading plate and 3/8 inch eye bolt to the selected loading position. A mechanical sighting device will mark the bottom of the loading block (or top of the loading plane). This is defined as the "zero" reference (starting point) for measuring bridge deflection. The minimum load of 2 kg is then applied to the bridge (as described in 3a above).
2. The load will be applied by the participant regulating a flow of sand from a reservoir tank by means of a "throttle device" -- a simple forward/backward two-handled mechanical lever that regulates the flow of sand into a loading bucket. participants will be permitted to direct this flow with their free hand, but may not touch the sides, handle or bottom of the bucket itself. This includes any part of the testing device. If failure occurs (see 4c) the throttle must be closed immediately. An experienced judge will be on the opposite two-handled throttle to ensure this closure. An effort to impede this closure will result in disqualification. The maximum load supported by any bridge will be 50 kg. Any amount over this quantity, will not count in the calculation of the bridge's efficiency. The testing device itself will have the equivalent of 52 kg of sand in the reservoir.
3. Bridge failure is defined as the inability of the bridge to carry additional load, or a load deflection of 15 mm, whichever occurs first.
4. The bridge with the highest structural efficiency, E, will be declared the winner.

1. All construction and material requirements will be checked prior to testing by the judges. Bridges that fail to meet these specifications at the conclusion of the allowable time for checking will be disqualified. Bridges disqualified prior to the start of the contest may be tested as exhibition bridges at the discretion of the builder and the contest directors.
2. If, during testing, a condition becomes apparent (i.e., use of ineligible materials, inability to support the loading plate, bridge optimized for a single loading point, etc.) which is a violation of the rules or prevents testing as described above in Section 4, that bridge shall be disqualified. If the disqualified bridge can accommodate loading, it may still be tested as an exhibition bridge as stated above.
3. Decisions of the judges are final; these rules may be revised as experience shows the need. (Please check our web site, http://www.iit.edu/~hsbridge, after January 15, 2010, to learn whether any changes have been made.)