2012 Chicago Regional Bridge Building Specifications


These rules have been developed by the Chicago Regional Bridge Building Committee for the Thirty Sixth Chicago Regional Bridge Building Contest to be held on Monday, February 6, 2012 at Illinois Institute of Technology, Chicago IL 60616, USA. If you have a question about these rules, FIRST take a look at the list of Frequently Asked Questions (FAQ) to see if the answer is already there. If you have read the FAQ, and still have a question about the contest rules, then you may contact the Chief Judge, Jamal Grainawi at grainawi@pbworld.com. For questions on any contest topic EXCEPT the rules please contact Prof. John Kallend at kallend@iit.edu.

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.


1. Materials
  1. The bridge must be constructed only from 3/32 inch square cross-section basswood and any commonly available adhesive.
  2. The basswood may be notched, cut, sanded or laminated in any manner.
  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 (see Figure 1) must span a gap (S) of 300. mm, have a minimum clearance (C) of 50 mm above the support surface at mid-span, be no longer (L) than 400  mm, be no taller (H) than 200 mm above the support surfaces, no wider (W) than 80 mm and no narrower than 25 mm at the loading surface.
  3. The bridge must be constructed to provide a horizontal support for the loading plate and at the three loading locations described in 2d. Any portion of the structure below the loading surface must provide clearance for the loading rod (see 3c) to be mounted from below.
  4. The load will be applied with the center of the plate at one of the three (3) loading locations on the longitudinal axis of the bridge: 1) the center, 2) 25 mm to the right of center, and 3) 45 mm to the left of center (see Figure 1). The three loading locations must lie in the same horizontal plane. The loading plane must be located on the roadbed and lie no more than a distance (P) of 100 mm above the base of the bridge (support surface).
  5. The bridge must be constructed to allow a standard Ping-Pong ball, 38.1 mm diameter to be rolled along the roadbed, from end to end without falling off or through the bridge. To test this requirement, the bridge will be placed at a 20 degree angle (from horizontal) and the ball will be placed on one end of the roadbed then released. The ball must roll freely from one end to the other. The roadbed must be continuous, horizontal, and at least 250 mm (R) in length.
  6. The bridge structure may not project below the support surfaces (see Figure 1).
3. Loading
  1. The load will be applied by means of a 35. mm square plate that is between 6 mm and 13 mm in thickness. A 9.53 mm (3/8 inch) diameter eyebolt is attached from below to the center of the plate (see Figure 2). The plate will be horizontal; it will not pivot on the eyebolt, and during testing the sides of the plate will be placed parallel to the longitudinal axis of the bridge.
  2. The load will be applied with the loading plate centered at one of the three positions described in section 2d. Masses will be supported on a vertical loading rod suspended from the eyebolt. The minimum initial load will be 2. kg.
4. Testing
  1. On the day of the competition, the judges will decide which one of the three loading locations will be used for the competition; it will be the same for all bridges.
  2. The loading plate will be located on the bridge at the specified loading location. The load will be applied from below, as described in section 3a above. On the day of the contest, contestants 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.
  3. Competition loading will stop at 50. kg. However, loading will continue until the bridge experiences failure. Bridges failing above 50. kg will be considered to have held 50. kg for efficiency calculation.
  4. Bridge failure is defined as the inability of the bridge to carry additional load, or a load deflection of 25.4 mm under the loading location, whichever occurs first.
  5. The bridge with the highest structural efficiency, E, will be declared the winner.

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. 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://bridgecontest.phys.iit.edu after January 7, 2012, to learn whether any changes have been made.



Last update: November 1, 2011
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For further information, contact: Prof. John Kallend - kallend@iit.edu, Illinois Institute of Technology
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