Association for Bridge Construction and Design WESTERN NEW YORK CHAPTER

The model bridge must be built in accordance with the following instructions:

REGULATIONS

A. Have fun and enjoy the design process!

B. The material to be used for each structure shall consist of balsa wood and glue. The weight of each structure shall be less than 300 grams (10.6 oz.).

C. See attached Figures for required bridge dimensions.

D. The bridge and deck shall be provided with a ½” diameter hole at the geometric center of the structure (center of bridge length, center of bridge width) so there is clearance for a ½” diameter rod to extend downward from this hole to facilitate set up of the testing device.

E. Specific definitions:

a. Failure: failure is determined:

1. by the bridge collapsing from the load placed on the test block by the testing device;
2. by the superstructure below the deck touching the face of the testing de-vice; or
3. the structure is unable to carry any increased load from the testing device after 5 consecutive pumps to apply load.

b. Deck: the part of the bridge that is meant to be traveled on by a vehicle.

1. The deck must extend the full length of the bridge and maintain a vehicular roadway area without any obstruction.
2. The deck shall be constructed using a single, solid, balsa wood sheet. The balsa wood sheet used for the deck may not be more than ¼” thick.
3. The deck shall be level (or flat) and shall not be curved (or arched).

A. The structure is weighed before testing and the weight is recorded on the evaluation form.

B. An increasing load is applied to the structure via the testing device until the structure fails. The load will consist of a uniform load, applied over a 2” wide and 4” long area on the deck at the center of the structure.

C. The Failure Load is recorded.

D. The efficiency is determined by the following equation:
(Failure Load – Device Calibration Load) / (Structure Weight)
Device Calibration Load = Spring Constant for Testing Device

E. The efficiency is recorded.

F. The winner is determined by a point system as follows:

Aesthetics - 10 pts - An independent judge will walk around during the competition and assign a score to each bridge based on the following criteria:

• Complexity - The number of purposeful members involved in the de-sign, for example a truss bridge will score better than a girder bridge. (3 pts.)
• Engineering - How much thought is placed into the design, where the connection points are, how connections are made, and what member shapes are used in the design. (3 pts.)
• Workmanship - A bridge that is "clean", such as nice glued edges, members matching at connections and nice sanded edges. (4 pts.) For example, truss and arch style bridge will be given a higher score than a flat slab style bridge.

Efficiency - 30 pts - Calculation from step D.

G. The best possible score will be 40 points. In case of a tie, the first prize will be awarded to the structure, which in the opinion of the judges, displays the best application of Civil Engineering principles, innovative ideas, and general overall appearance.

H. The judges decisions will be final.

SUBMISSION

Model bridges shall be submitted at the ABCD contest table on the date of the competition. Trophies will be presented at the conclusion of the contest. Certificates will be given to all that participate.

EXAMPLES OF MODEL BRIDGES THAT MEET THE RULES These examples are not shown to minimize the amount of effort that a particular student put into their bridge. These examples are for reference only. (Click on image for larger view)

EXAMPLES OF MODEL BRIDGES THAT DO NOT MEET THE RULES These examples are not shown to minimize the amount of effort that a particular student put into their bridge. These examples are for reference only. (Click on image for larger view)

Website created by: ABCD WNY Chapter
Please direct all questions and comments regarding this site to: kcox@monroecounty.gov

Last Updated: January 25, 2008
© 2008 Association for Bridge Construction and Design, WNY