2017 Chicago Regional Bridge Building Specifications
These rules have been developed by the Chicago Regional Bridge Building
Committee for the Forty-Second Chicago Regional Bridge Building
Contest to be held on Tuesday, January 24, 2017 at Illinois
Institute of Technology, Chicago IL 60616, USA. If you have a question
about these rules that is not answered by our FAQ, please please direct it to Mr.
George Krupa, by e-mail at email@example.com. For questions on any
contest topic EXCEPT the rules please contact Prof. Carlo Segre
The object of this contest is to see who can design, construct and test
the most efficient bridge within the specifications. Model bridges
are intended to be simplified versions of real-world bridges, which are
designed to permit a load to travel across the entire bridge. In order to
simplify the model bridge design process, the number of loading positions
is reduced, 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 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 and any commonly available adhesive.
The basswood may be notched, cut, sanded or laminated in any manner.
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 30.00 grams.
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, be no taller (H) than 150. mm
above the support surfaces. The bridge must be constructed to
permit a clearance (C) of 20. mm above the support surface
at the midpoint of the span. No part of the bridge
may extend below the support surface.
The loading plane (P) shall be horizontal and shall lie between
30. mm and 40. mm above the support surfaces.
The bridge must be constructed to provide for the placement of the
loading plate (see section 3, below) at each of
the two loading points. Any portion of the structure above and
below the loading plane must provide clearance for the loading rod
at the two loading point locations.
The load will be applied downward, from below, by means of a
40.0 mm square plate (see Figure 2) resting on the loading plane
of the bridge. The plate will be between 6. mm and 13. mm
thick and will have a 9.53 mm (3/8 inch) diameter eyebolt
attached from below at its center.
The two edges of the loading plate will be parallel to the
longitudinal axis of the bridge at the time of load application.
The load will be applied on the longitudinal axis of the bridge at one
of two loading points: 60. mm to one side, and 20. mm to the
other side of the center of the 300. mm span.
On the day of the contest, judges will decide the exact loading
location to be used. It will be the same for all bridges.
On the day of the contest, participants will center their bridge on
the loading surfaces with the loading plate and 3/8 inch eye bolt
at the selected loading position.
The load will be applied by the participant until bridge failure. The
maximum scoring load supported by any bridge will be 50 kg. Any
amount over this quantity will not count in the calculation of the
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.
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
All construction and material requirements will be checked prior to
testing. Bridges failing to meet these specifications at the
conclusion of the allowable time for checking-in will be disqualified.
Bridges disqualified prior to the start of the contest may be tested
as unofficial bridges at the discretion of the builder and the contest
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.
Decisions of the judges are final; these rules may be revised as
experience shows the need. Please check our web site,
after January 5, 2017, to learn whether any changes have been made.
Last update: October 23, 2017
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For further information, contact: Prof. Carlo Segre -
Illinois Institute of Technology
© International Bridge Building Committee, 2017