Bridge Building Contest Rules
These rules have been developed for the 2008 41st Annual Colorado High School Bridge Building Contest to be held on Saturday, February 23, 2008 at Bureau of Reclamation Engineering and Research Laboratories, Building 56 at the Denver Federal Center. Questions about these rules should be directed to John Migliaccio at jmigliaccio@jrengineering.com. The object of this contest is to see who can design, construct and test the most efficient bridge within the following specifications. Note: Check these specifications as well as the posted Questions and Answers continually for critical changes, clarifications, additional requirements, tips, etc.
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 allow the contest to proceed in a reasonable amount of time only one loading position is actually tested.
1. Materials
a. The bridges must be constructed only from 3/32-inch square cross-section basswood and any commonly available adhesive. This PEC website lists several suppliers of the basswood under the Competition Guidelines page.
b. The basswood may be notched, cut, sanded or laminated in any manner but must still be identifiable as the original basswood.
c. No other materials may be used. The bridge may not be stained, painted, or coated in any fashion with any foreign substance.
2. Construction
a. The bridge mass shall be no greater than 25.00 grams.
b. The bridge (see Figure 1) must span a gap (S) of 300 mm, be no longer (L) than 400 mm, have a maximum width (W) of 80 mm, and be no taller (H) than 200 mm above the support surfaces.
- No portion of the bridge, including the loading plane, shall extend below the top of the support surfaces. This applies to the un-loaded condition. Deflections below the support surface during loading will be permitted.
- Any portion of the structure above or below the loading plane must provide clearance for the loading rod at the location of the loading plate.
- 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.
- The loading plane (P) shall be level horizontally along the axis of the bridge for a minimum of 25 mm each side of the loading point to accommodate the loading plate. The minimum width of the loading plane (perpendicular to the span, or bridge axis) at the loading point shall be 30 mm.
3. Loading
a. 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 shall not pivot during the loading.
b. The two edges of the loading plate will be parallel to the longitudinal axis of the bridge at the time of load application (i.e., the loading plate will not be rotated in order to allow the plate to be supported).
c. The load will be applied on the longitudinal center axis of the bridge with the loading plate centered over the 300 mm gap.
4. Testing
a. The bridge will be centered on the support surfaces.
b. 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.
- The load will be increased until failure occurs.
d. Failure is defined as the inability of the bridge to carry additional load or a load plate deflection of 25 mm, whichever occurs first.
e. The bridge with the highest structural efficiency, E, will be the winner, where
Load supported in grams
E = -----------------------------------
Mass of bridge in grams
5. Qualifications
a. 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.
b. 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.
c. The decisions of the judges will be final. These rules may be revised as experience shows the need (please check the Professional Engineers of Colorado Bridge Building web site at http://www.pec.org/PEC%20Bridge%20Building.html periodically after October 31, 2007.)
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Professional Engineers of Colorado
3030 W 81st Avenue
Westminster, CO 80031
Phone: 303-480-1160
Fax: 303-458-0002