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Competition Details & Guidelines

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​The N.C. Department of Transportation is currently accepting entries for the 2025 Model Bridge Building Competition. Entries are now being accepted until March 3, 2025.

Regional Competition

The regional competition will be held on March 7, 2025.

State Final Competition 

​The State Final Competition will be held on April 25, 2025. 


​​​Guidelines​ - New for 2025

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  • Introduction

    2025 Model Bridge Buillding Competition Guidelines

    Entries will be accepted until March 3, 2025. ​

    **Entries that do not meet all construction specifications will not receive a bridge efficiency score. NO EXCEPTIONS**

    Note: Middle school teams will not compete against high school teams.

    The object of this competition is to design, construct and test the most structurally efficient model truss bridge using the specifications. Important information for this year’s competition includes:

    • Minimum clear span of 18 inches. Maximum bridge length of 22 inches.
    • Laminated members are not allowed.
    • The bridge must not weigh more than 30 grams.
    • Members may not be wider than 1/8 inches or deeper than 1/8 inches.
    • The bridge deck must extend the entire length of the bridge and maintain a "vehicular roadway" without any obstruction (2 inches wide x 2 inches high). The bridge deck shall be level (or flat) and shall not be curved (or arched). The bridge deck shall be constructed using a single, solid, balsa wood sheet. The balsa wood sheet used for the deck must be 1/16 inches thick. The bridge deck should be the full width of the “vehicular roadway” and extend the entire length of the bridge’s longest dimension.
    • To allow for testing, there must be a half-inch hole at midspan in the bridge deck. There must be no obstructions below the hole that would prevent the passage of the testing rod.
    • The model bridges will be loaded initially with only the bucket and testing apparatus. Dry sand will be added after the initial loading until the bridge collapses.
    • Submit one PDF file of your design drawing and original written report.
    • PowerPoint presentations are not permitted at the regional competitions​
    **Regional Competitions:  Due to space limitations at the facilities where the regional competitions are held, please notify Mrs. Sterling Johnson with NCDOT if your group, including students, teachers and chaperones, is larger than 20 people.  ​


  • Construction Specifications
    1. Kits of balsa wood and glue will be provided to each competing school and should be enough for 2-3 trial bridges and a final bridge for the competition.  Schools may choose to purchase materials for themselves from other vendors. The materials used in the construction of ​the bridge shall consist only of commercially ​available balsa wood and glue.

    2. Any type of bonding material (glue) may be used.

    3. A bridge may not be coated with any material (i.e. paint, stain, or glue).

    4. The bridge shall contain no member wider than 1/8 inch nor deeper than 1/8 inch. This member size ​requirement does not apply at the intersection of members. Gussets, dowels a​nd mitered joint connections are allowed, but only at the joint areas. They can be no thicker than 1/8 inch and no larger than a 1/2 square inch in area. Individual members shall be constructed of a ​single piece of balsa wood. Laminated members are not allowed​.

    5. The bridge shall be a minimum of 2 inches wide and must allow a 2-inch x 2-inch cube to be passed along the length of the bridge ("vehicular roadway" with no obstructions, referenced above). The ​maximum length of the bridge shall be 22 inches.

    6. The bridge must have a minimum clear span of 18 inches between supports. Your bridge must allow a 3-inch x 3-inch cube to be passed beneath it at mid-span, measured while the end supports are resting on a flat surface. The bridge shall be freestanding.

    7. The bridge deck shall be the full width of the “vehicular roadway” and extend the entire length of the bridge’s longest dimension. There must be a 1/2 inch hole at mid-span in the bridge deck to allow for testing. There must be no obstructions below the hole that would prevent the ​passage of the testing rod.​




  • Testing
    ​A 1-1/2-inch wide x 3-inch long x 1/2-inch thick loading plate will be positioned over the hole in the deck at midspan, and placed directly on the balsa wood deck. 

    There will be no use of steel bars to elevate the plate above the d​eck. A testing rod will fit through the 1/2 inch hole in the balsa wood deck and attach to the loading plate. An initial load will consist of an empty container suspended from the ​testing apparatus. Sand will be added to the container at a slow, steady rate until the bridge collapses. 


  • Additional Requirements
    1. Draw a diagram of your bridge to scale. This can be done by hand or by using a computer ​program. Submit a PDF file of your bridge de​sign.

    2. Using your diagram, create a model of your bridge from your materials.​

    3. Write an original, 12 font sized, doubled spaced, three (3) page essay with one in​ch margins that ​includes:

    • Research on bridge building history ​and construction.
    • Identification of career areas used in the design and construction of bridges.
    • Describe the process used to finalize bridge design and incorporate but not limit to the following terminology: 
    ○​ Compression
    ○ Joint
    ○ Engineer
    ○ Live Load
    ○ Span
    ○ Tension
    ○ Truss
    ○ Top Chord
    ○ Bottom Chord
    ○​ Dead Load

    Students also may incorporate infor○mation about the following questions:

    • Why do we need bridges? What purpose do they serve?
    • How are bridges able to hold the tremendous amount of weight they hold?
    • Why is it important to know whether parts of a bridge will be subjected to tension or compression?
    • What is a polygon?
    • Why is a triangle the strongest polygon?
    • Why is it important to first create a scale drawing and model of a bridge before the actual construction begins?
    • What materials are essential to design a scale drawing?
    • What geometric shapes did you use in the bridge model? Why?
    • How does the strength of the bridge compare to the weight of the bridge?
    • What should you do to design a bridge for the future?
    • How can computers help design bridges?

    For information about bridges, we recommend the following website - Building Big Bridges​. You can learn general information about bridges by viewing the “Bridge Basics” section and learn more about the forces that act on a bridge by viewing the "Forces Lab​" section. The website also ​includes information about significant bridges throughout history​. 


  • Judging Criteria
    ​A panel of judges will evaluate the bridge model using the following criteria:

    Teams can receive a maximum score of 30 for the following three categories.

    Oral Presentation (Score 1-10)

    You are promoting the bridge you designed and built for your client -- the judges. Demonstrate knowledge of bridge design and construction. In the oral presentation, describe the chosen design and explain the rationale behind the bridge design. Presentations at both regionals and finals may not exceed seven minutes including set up and break down. Content is critical and will be the ​main consideration in judging your presentation.

    **Remember, PowerPoint Presentations are not permitted at the regional competitions.**

    Written Report (Score 1-10)

    An original report must be written according to the guidelines outlined in the bridge model requirements. It must also include your research information.

    Design Drawing (Score 1-10)

    All bridge models must be accompanied by a scale drawing of the bridge according to the ​guidelines in the bridge model requirements. 
  • Bridge Efficiency Score
    ​The bridge efficiency score is determined independently from the three categories above.

    Bridge efficiency score equals 0.10 times the weight carried (in grams), divided by the weight of the bridge (in grams). 

    The maximum weight carried by the bridge will be 20 kilogram.  If the bridge carries more than 20 kilogram, only 20 kilogram will be used to calculate the bridge efficiency score.  No additional credit will be given for carrying more than 20 kilogram. 

    The calculated load carrying score will then be added to the numbers from the oral, written, and design drawing scores to create a total score.

    The winning bridge will be the model with the highest combined score from the four categories. In the event there is a tie, the model with the lowest weight to load carried ratio ​will be the winner.

    **Decisions made by competition judges an​d testers are final. There is no dispute resolution ​process; however, input for process improvement is encouraged.


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Frequently Asked Questions

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  • Will middle school teams compete against high school teams?
    ​No. We will have separate competitions for middle schools and high schools.
  • Can teachers or schools enter more than one model bridge?
    No. We will accept one model bridge entry per school.
  • Can individual students enter the competition?
    ​The competition is designed to encourage students to work in teams with the teachers acting as facilitators. Therefore, the N.C. Department of Transportation strongly encourages teams of at least two students with one or more teachers as facilitators. If it is impossible for a school to develop such a team, then a student with a teacher as a facilitator will be allowed to enter the competition.
  • Are you offering the competition next year?
    ​Yes, the competition is an annual event.

11/22/2024 3:34 PM