2013 International Bridge Building Specifications


These rules have been developed by the International Bridge Building Committee for the 2013 International Bridge Building Contest to be held on April 27, 2013 at Illinois Institute of Technology, Chicago IL 60616, USA. Questions about these rules should be directed to Dr. John Kallend, by email at kallend@iit.edu.

In order to receive official wood and participate in the contest, a High School student must have placed first or second in a Regional Contest ant be reported, by the Regional Coordinator, to Prof. john Kallend, MMAE Department, IIT, Chicago, IL 60616, by mail or e-mail at kallend@iit.edu. Two bridges from a single region must appear to be of different design. 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 these 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. In order to simplify the model bridge design process, the number of loading positions has been reduced to three, and to allow the contest to proceed in a reasonable amount of time, only one loading position is actually tested. These simplifications do not negate the requirement that the bridge must be designed to accept a load at any of the three positions. Bridges determined by the judges to not meet this requirement will be disqualified and tested as unofficial bridges.


1. Materials
  1. The bridge must be constructed only from 3/32 inch square cross-section basswood included in the kit and any commonly available adhesive.
  2. The basswood may be notched, cut, sanded or laminated in any manner but must still be identifiable as the original wood.
  3. No other materials may be used. The bridge may not be stained, painted or coated in any fashion with any foreign substance.
2. Construction
  1. The bridge mass shall be no greater than 25.00 grams.
  2. The bridge shall rest on two support surfaces separated in elevation (E) by 10. mm and horizontally by a gap (S) of 300. mm (see Figure 1).
  3. 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 150. mm above the upper support surface, and no wider (W) than 80. mm at the loading surface. No part of the bridge may extend below the lower support surface.
  4. The bridge must be constructed to provide a horizontal support for the load (see section 3b) at each of the three loading locations described. Any portion of the structure below the loading plane must provide clearance for the eyebolt which extends below the loading plage (see Figure 2).
  5. The load will be applied with the center of the plate at one of three possible loading locations on the longitudinal axis of the bridge: The center and 50. mm to either side of the center (see Figure 1). The three loading locations must lie in the same horizontal loading plane a distance (P) of 10. to 50. mm above the upper support surface.
3. Loading
  1. On the day of the contest, an independent judge will decide which one of the three loading locations will be used. The same loading location will be used for all bridges. Competition loading will stop at 50. kg, however, loading will continue until bridge failure (see section 4d).
  2. The load will be applied by means of a 40.0 mm square plate that is at least 6 mm but less than 13 mm thick. A 9.53 mm (3/8 inch) diameter eyebolt is attached from below to the center of the plate (see Figure 2). During loading, the edges of the plate will be parallel to the longitudinal axis of the bridge.
  3. Masses will be supported on a vertical loading rod suspended from the eyebolt. The minimum initial load will be 2..00 kg.
4. Testing
  1. The bridge will be centered on the support surfaces.
  2. The loading plate will be placed on the bridge at the specified loading location determined on the day of the contest.
  3. The load will be applied from below, as described in section 3.
  4. Bridge failure is defined as the inability of the bridge to carry additional load, or a load deflection of 25. mm under the loading location, whichever occurs first. If a bridge has leg(s) which fail, the bridge will have failed regardless of deflection.
  5. The bridge with the highest structural efficiency, E, will be declared the winner. Bridges failing above 50. kg will be considered to have held 50. kg for efficiency calculation.

E = Load supported in grams (50,000g maximum) / Mass of bridge in grams

5. Qualification
  1. All construction and material requirements will be checked prior to testing. Bridges failing to meet these requirements will be disqualified. If physically possible, disqualified bridges 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.
  3. Decisions of the judges are final; these rules may be revised as experience shows the need. Please check our web site, http://bridgecontest.phys.iit.edu after January 7, 2013, to learn whether any changes have been made.



Last update: February 19, 2013
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For further information, contact: Prof. Carlo Segre - segre@iit.edu, Illinois Institute of Technology
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