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2013 Colorado Bridge Building Contest Specifications

1. Materials
   1. The bridges must be constructed only from 3/32-inch square cross-section basswood, cables and any commonly available adhesive. This PEC website lists several suppliers of the basswood under the Competition Guidelines page.
   2. The basswood may be notched, cut, sanded or laminated in any manner but must still be identifiable as the original basswood.
   3. Cables may be any flexible non-metallic material such as string or fishing line. Metallic wire is not permitted.
   4. 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 28.00 grams.
   2. Bridge outer dimensions (see Figure 1):
      • The bridge must span a gap of 300 mm.
      • The bridge shall be no longer than 400 mm.
      • The bridge shall have a maximum width of 100 mm.
      • The bridge shall be no taller than 60 mm above the support surfaces.
      • Maximum overall depth from the top of the bridge to the bottom of the bridge shall not exceed 75 mm. (Bridge may extend 15 mm below support surface.)
   3. Dimension limits above applies to the un-loaded condition. Deflections these limits during loading will be permitted.
   4. The bridge construction must provide clearance for the application of the loading rod and loading plate at the location specified in Figure 1.
   5. The bridge shall include a loading plane to which the testing load will be applied. The bridge’s loading plane must be constructed to provide support for the loading plate (see Section 3 below) at the loading point.
   6. The loading plane (P) shall be horizontal and shall lie between 5 mm and 15 mm above the support surface.
3. Loading
   1. The load will be applied downwards (from above) by means of a 50 mm square loading plate (see Figure 2) resting on the loading plane of the bridge. The plate will be attached to the rod from above to the center of the plate. The bottom plate surface will be horizontal and will not pivot during the loading.
   2. The load will be applied at one third-span of the bridge (100 mm from one end of the span.)
4. Testing
   1. The bridge will be placed on the support surfaces. The student may choose the orientation of their bridge, so as to place their intended loading plane location under the loading plate.
   2. The loading plate will be located on the bridge and the load will be steadily applied from above the bridge onto the specified loading location.
   3. The load will be increased until failure occurs.
   4. Failure is defined as the inability of the bridge to carry additional load or a load plate deflection of 25 mm, whichever occurs first.
   5. The bridge with the highest structural efficiency, E, will be the winner, where:
       

      E =	Load supported in grams
      	Mass of bridge in grams

5. Qualification
   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, etc.) which 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. The decisions of the judges will be final. These rules may be revised as experience shows the need (please check the National Society of Professional Engineers Bridge Building web site at nspe-co.org/BridgeBuilding.html periodically.)

National Society of Professional Engineers - Colorado Chapter
Box 261354, Lakewood, CO 80232
Phone: 303-973-8010
Fax: 303-979-6094