Page 1 of 6

2018 Bridge Building Contest Rules

2018 Bridge Building Contest

Sponsored by

Foreword
This contest is limited to SIX entries per school.

Each school MUST preregister online by February 6, 2018. Visit oef.org for registration information. Upon check-in
the day of the event, you will receive the contest entry forms, which your students will fill out and turn in to the
contest directly. Prizes will be awarded to winning entries from registered schools (entries from unregistered
schools will NOT be eligible for prizes).

Design
Prior to the Fair a STUDENT bridge builder must design and build his/her own bridge. All design and building
techniques should fall within the specifications that follow. Tolerances are given in the specifications. Should any
bridge fall outside the tolerances, that bridge will be disqualified or the builder may attempt on-the-spot
modifications to bring the bridge within specifications. Each bridge must be free standing.

Note: While adults may aid the student with suggestions, etc., the bridge must be built ONLY by the student 
NO ADULT CONSTRUCTION ASSISTANCE IS PERMITTED.

Materials
1. Square or round wood toothpicks (Standard restaurant size – 2.75 inch, tapered ends) (unlimited quantity) No
skewer or ‘pick’ type toothpick cut to size, No Bamboo or plastic toothpicks, no “Craft” toothpicks.
STRUCTURES BUILT FROM OTHER TOOTHPICKS WILL BE DISQUALIFIED.
2. Elmer’s Carpenters wood glue or Elmer’s School Glue. (NO COLORED GLUES OR EPOXY BASED GLUES.
STRUCTURES BUILT FROM OTHER GLUES WILL BE DISQUALIFIED.)
3. Kite String (NEW FOR 2017). Students may use up to four (4) lengths of common, white, cotton kite string (no
yarn, fishing line, nylon, or other plastic string). Each of the four lengths should not exceed seven (7) inches
when measuredin their final in-place loation on the bridge.
3. One (1) metal eye bolt with 1/4" diameter shaft, washers and nut.
4. Loading Block: Block of wood with dimensions not to exceed 3" x 3" x ½". The block is used to attach the eye
bolt to the bridge. A minimum dimension of 2 ½” x 2 ½” is recommended.
5. Materials list of brand and type of glue and toothpicks used. Students are encouraged
For ease of conformance to
to bring the bottles/boxes (or their labels and a sample of an unmodified toothpick)
with them in the event that any questions arise as to construction materials. the geometry tolerances,
Geometry the student should strive to
construct a bridge that
1. Length: 24" (+/– ½"). meets all the MINIMUM
2. Width: 5” (+/– 1"). dimensions (including
3. Height: Maximum 6” (excluding eye bolt). See the Structural Efficiency roadbed clearance
criteria below for more height considerations. requirement) while still
4. Weight: Maximum 11 oz. (excluding eye bolt). See the Structural Efficiency being able to fit inside a
criteria below for more weight considerations. 24 ½” long x 5” tall x
5. Roadbed: Bridge must have a flat roadbed. The area above the roadbed 4 ½” wide box.
must accommodate a 1-5/16"O.D. (outside diameter) pipe.

2018 OEF Engineering Fair Contest Rules

Revised 10/01/2018
 Page 2 of 6
2018 Bridge Building Contest Rules

GEOMETRY EXAMPLE. . .

Geometry Notes

1. The eye bolt must be located in the center of the bridge and be large enough to pass a ¼" diameter
"S" hook through its eye. The "S" hook is part of the testing apparatus (“Bridge Breaker”) and is
provided by the judges.

2. The eye bolt is attached to the Loading Block; the block should sit on the top of the roadbed (see
above) and be supported by the roadbed, but should not be attached (e.g. glued) to the bridge. The
Loading Block and shaft of eye bolt may protrude ABOVE the roadbed. Bottom of eye bolt MUST
protrude a minimum of 1" but not more than 2" BELOW the end supports of the bridge.

3. The Loading block is used to transfer the load from the “Bridge Breaker” to the bridge. The larger
the block of wood, the better it will transfer the load. Students should consider using the largest
Loading Block that can fit inside the roadbed without exceeding the maximum sizes listed above (3
½” to 4 ½” square).

Additional Rules & Remarks

Toothpicks may be cut or glued. GREATER THAN 75% OF

EACH TOOTHPICK (WHETHER WHOLE OR CUT) MUST BE
VISIBLE THEREFORE: NO GROUPS OF MORE THAN TWO (2)
TOOTHPICKS!

Only use the approved glues: Elmer’s Carpenter’s Wood Glue

or Elmer’s School Glue.

The over-use of the approved glues typically does not result in

satisfactory load capacities; i.e. “soaking,” “dipping,” or
otherwise coating random configurations of toothpicks in glue
will not be looked upon favorably by Aesthetics and
Construction Quality judging and has historically resulted in
substantially lower bridge load capacities.

ATTN!!! Label your bridge: A tag tied to the bridge or a single

piece of masking tape looped around a member with the
student(s) name(s) to ease in tracking the bridge through
registration and judging is appreciated.
2018 OEF Engineering Fair Contest Rules
Revised 10/01/2018
 Page 3 of 6
2018 Bridge Building Contest Rules

2018 OEF Engineering Fair Contest Rules

Revised 10/01/2018
 Page 4 of 6
2018 Bridge Building Contest Rules

Students and instructors are encouraged to research various bridge design types, specifically trusses,
when designing their bridges. Look for efficiencies such as least number of members and shallow
depths. Pay attention to tension and compression member locations and the path the load will follow
through the loading block into the truss and then to the supports. Strengthen this path and minimize
portions of the bridge that don’t fall in that load path. Consider how the truss will behave during
loading: Will it twist? How would I prevent that twist? Can the kite string be used as a compression
member? Does the length of diagonals affect how strong the bridge is?

During Load Capacity testing, the students and spectators must stand outside the designated “Debris
Zone” to avoid being hit by any bridge piece(s) that may be ejected when/if the bridge fails. Students
and spectators are encouraged to take photos/video of the testing, especially “before” and “after”
photos. Students will be able to dispose of their bridges at the competition room or are free to take
their engineering creations with them at the conclusion of all testing and judging.

Judging

1. Decision of judges, during all phases of the competition, is FINAL. Any bridge that fails to meet
geometry criteria, weight criteria, or material restrictions and has been disqualified from the
competition may still be load tested at the judge’s discretion assuming adequate time remains after
all qualified entries have been tested and judged.

2. Students will receive a Bridge Building Entry Form at the registration desk. Students must submit
this form at the contest registration before 12 a.m. Judges will then inspect the bridge for
compliance with the rules and assign an entry number indicating student’s turn in sequence of
competing. Judges may alter the testing sequence as they see fit. All entries must be registered at
the contest location between 9:30 a.m. and 12:00 p.m. on Fair day. Contest volunteers will register
bridges beginning at 9:30 am, bridge “breaking” (testing for load Capacity) will begin at
approximately 10:30 am. Competition will run until all registered entries have competed.

2018 OEF Engineering Fair Contest Rules

Revised 10/01/2018
 Page 5 of 6
2018 Bridge Building Contest Rules

3. Judges will weigh, measure, and register each bridge prior to Load Capacity testing. If a bridge does
not meet the geometry or weight specifications, the entrant will be permitted a maximum of two
attempts to modify their bridge to meet specifications. The 1-5/16" pipe, scales and rulers will be
supplied by the judges.

4. The bridges will be competing in three categories Aesthetics and Construction Quality, Structural
Efficiency, and Load Capacity. Top three bridges (which comply with all rules) in each category will
receive prizes. The judging criteria for each category is as follows:

A. Aesthetics and Construction Quality category: Entries will be judged on the overall design of
the bridge and its consideration of engineering principles, design, and mechanics. Consideration
will be given to bridges that are constructed with care and precision as well as entries that show
ingenuity and creativity in appearance and form. Decorating the bridges is not required, but is
encouraged. The judges will award a 1 st, 2nd, and 3rd prize in this category.

B. Structural Efficiency category: Entries will be weighed and measured and these results, along
with the results from the Load Capacity category will be entered into a formula to generate a
Structural Efficiency Score for the bridge. Lower scores represent more efficient designs
compared to higher scores. Students wishing to excel in this category should strive for
maximizing the load capacity (up to a maximum value of 200 lbs) while trying to maintain low
weight in ounces and utilizing the shallowest bridge depth (height in inches). The three lowest
scoring bridges will be awarded prizes in this category. The formula used for the 2018 Structural
Efficiency Score is as follows:

1,000 x √ Height x Weight 1.5

Load
C. Load Capacity category: Entries shall be load tested by means of a custom "Bridge Breaker".
Judges will position the bridge on the tester with approximately 2" of each end of the bridge
resting on the tester. The "S" hook will be attached to the eye bolt and pressure will be applied
in a downward vertical direction. A load indicator will display pressure applied until the bridge
fails. Failure is determined when (a) the bridge collapses, (b) a deflection of the base of the
bridge exceeds one inch, or (c) the wood block causes a failure of the bridge roadbed. No
repairs or modifications are allowed once testing has begun. However, if the eye bolt fails
before the bridge fails, judges may choose to allow a new eye bolt to be placed on the bridge.
1st, 2nd, and 3rd prizes will be awarded in this category.

Prizes & Distribution

Contest winners will be announced on the Engineer Fair web page at http://
http://oef.org/programs/engineering-fair. Those entries winning prizes will be notified through their
teacher of record by email.

First, Second and Third place winners in each category will receive medals. The winning classrooms of
the First, Second and Third Place entries in the Load Capacity category will receive a cash award. In the
event of a tie, cash prizes will be equally distributed between winning entries.
ATTENTION!! Predict and Win: On each entry form on the day of the Fair, the student(s) responsible
for the bridge design and construction shall give their estimate of the bridge’s load capacity, in

2018 OEF Engineering Fair Contest Rules

Revised 10/01/2018
 Page 6 of 6
2018 Bridge Building Contest Rules

pounds, on the entry form. The bridge designer(s) who guesses the closest to the failure load will win
a special prize from ASCE!

2018 OEF Engineering Fair Contest Rules

Revised 10/01/2018