2018 Chicago Regional Bridge Building Specifications
These rules have been developed by the Chicago Regional Bridge Building
Committee for the Forty-Third Chicago Regional Bridge Building
Contest to be held on Tuesday, January 23, 2018 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, George Krupa at firstname.lastname@example.org. For questions on any
contest topic EXCEPT the rules please contact Prof. Carlo Segre at
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 25.00 grams.
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 support surfaces, and have a width
(W) no greater than 80. mm.
The bridge must be constructed to provide a horizontal support for the
loading plate and at each of the two possible loading positions.
These two positions (see 3c). The bridge structure must allow
the loading rod (see 3c) to be mounted from below.
The bridge must be constructed to allow a 48 mm diameter,
300. mm long pipe (1.5 inch schedule 40 PVC pipe) to be passed
horizontally across the bridge with the pipe's lower surface on the
loading plane (P) between 80. and 100. mm above the base
of the bridge. This pipe must touch both loading locations
simultaneously (see 3c).
The bridge structure may not project below the support surfaces (see
Competition loading will stop at 50. kg, loading will continue until
bridge failure (see 4d).
The load will be applied by means of a 40. mm square plate (see
Figure 2) with a thickness (t) of at least 6 mm but less
than 13 mm. A 9.53 mm (3/8 inch) diameter eyebolt is
attached from below to the center of the plate. The plate will be
horizontal and will be mounted with its edges 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. kg.
The load will be applied with the center of the plate at one of two
(2) possible locations on the longitudinal axis of the bridge:
30. mm to the left and 60. mm to the right of the center
of the bridge span (see Figure
1). The two loading locations must lie in the same horizontal plane.
This loading plane must lie a distance (P) between
80. mm and 100. mm above the base of the bridge.
On the day of the competition, the judges will decide which one of the
two loading locations will be used; it will be the same for all
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 with the
edges of the plate parallel to the longitudinal axis of the bridge.
The load will be applied from below, as described in section 3 above. Competition loading will stop at
50. kg. However, loading will continue until bridge failure (see
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.
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 and may be checked after testing. Bridges failing to meet
these requirements 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.
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,
http://bridgecontest.phys.iit.edu after January 9, 2018, to learn
whether any changes have been made.)
Last update: January 15, 2018
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For further information, contact: Prof. Carlo Segre -
Illinois Institute of Technology
© International Bridge Building Committee, 2017