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 firstname.lastname@example.org.
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 email@example.com. 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
The bridge must be constructed only from 3/32 inch square
cross-section basswood included in the kit and any commonly
The basswood may be notched, cut, sanded or laminated in any manner
but must still be identifiable as the original wood.
No other materials may be used. The bridge may not be stained,
painted or coated in any fashion with any foreign substance.
The bridge mass shall be no greater than 25.00 grams.
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).
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.
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).
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
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).
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.
Masses will be supported on a vertical loading rod suspended from the
eyebolt. The minimum initial load will be 2..00 kg.
The bridge will be centered on the support surfaces.
The loading plate will be placed on the bridge at the specified
loading location determined on the day of the contest.
The load will be applied from below, as described in section 3.
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.
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
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
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.
Decisions of the judges are final; these rules may be revised as
experience shows the need. Please check our web site,
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 -
Illinois Institute of Technology
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