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Bridge Design Event

Design Constraints

Event Coordinator: Ken Moliterno DESCRIPTION

 The objective of this project is to design and build the lightest bridge capable of supporting a given load.  The bridge is a cantilevered wooden structure, which will be attached to a vertical- testing wall at one end, and supporting a load at the distal end.




1.       The bridge is to be a SINGLE structure constructed of wood and bonded by glue.  No other materials shall be used.  Bamboo is NOT a wood.

2.      The bridge must be constructed of pieces of wood no larger than ¼” high and ¼” wide.  Any dowels used cannot have a diameter greater than 1/4”.

3.      It may have an attachment base which may be of any type of wood not to exceed 30 cm x 15 cm x ½” thick.  The attachment base MUST be permanently attached to the bridge.

4.      Particleboard, wood products, or commercially laminated wood may not be used, except for the attachment base.

5.      There is no limit on the length of individual wood pieces used in the construction, with the exception noted for the attachment base.

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


1.       All construction must be completed prior to ____________________________________.

2.      Sound engineering practices such as good truss construction, gussets and mitered joints are encouraged.

3.      Do not coat the bridge with any materials (i.e. paint, stain, or glue).

4.      Unlimited lamination (i.e. bonding together layers of wood) by the student is allowed.

Commercially laminated wood is only allowed for the attachment base.

5.      The bridge must be constructed to meet the following parameters:

a.       It must be designed in such a way that it can be attached to the vertical-testing wall with one or two ¼” bolts.  The bolts will be precisely 20 cm apart on center horizontally.  The bridge may have an attachment base (which may be one or two separate pieces) or designed in such a fashion that it can be attached to the Testing Wall.

b.      The bridge must support the loading block at a minimal horizontal distance of 40 cm from the vertical-testing wall.

c.       No part of the bridge may touch the vertical-testing wall further than 15 cm below the attachment holes.


1.       All bridges will be assessed prior to testing for construction requirements and dimensions.

2.      Students must wear eye protection during loading and testing.

3.      The loading block, testing wall, attachment hardware and loading material will be provided.

4.      The vertical testing wall will be a piece of ¾” thick plywood or other suitable material around 45 cm wide and 30 cm high with two ¼” diameter holes 20 cm apart on center horizontally 5 cm from the top.

         5.      The bridge will be attached to the vertical-testing wall with one or two 2 inch long ¼”                threaded bolt(s), washers (not to exceed ¾”diameter) and wing-nuts through the holes in the              testing wall.  The bolts will be placed so that the head of the bolt is on the same side as the              bridge.

6.      The center of the loading block will be placed on the bridge beam a minimum of 400 mm from the vertical-testing wall.  Remember that the loading block is 50 mm wide so the length of the bridge should be GREATER than 400 mm.

7.      The load will be applied to the loading block by an eyebolt and S-hook.

8.      The loading block will be 50 mm long and 50 mm wide and 20 mm high.

9.      A bucket will be attached to the S-hook, and the S-hook is attached to the eyebolt on the loading block.

10.  The student will add sand to the bucket.

11.   The maximum allowable time for set up and loading will be ten minutes.  If the time expires, the bridge is ranked with those that could not hold the 15kg.

12.   The student will add sand to the bucket until failure occurs or the maximum load (15 kilograms, 33lbs) is supported.  The maximum load (15 kg) incorporates the total mass of the loading apparatus, bucket and sand.

13.   Bridges that experience failure before reaching 15 kilograms will not be disqualified.

14.   Failure is defined as the inability of the bridge to carry additional load without breakage or the inability to hold the maximum load for 5 seconds.  Excess sand added after failure will be removed.


1.     The score (Structural Efficiency) will be determined by the equation:

Structural Efficiency = Load supported (grams)/Mass of Bridge (grams).  The maximum load supported cannot excel 15 kg.

2.      The bridge that held all 15 kg for 5 seconds with the highest structural efficiency would be the winner, while others with lower efficiencies would place next.

3.      Bridges that meet all the specifications under Materials and Construction, but did HOLD the entire 15 kg will be ranked next.

4.      All bridges with Construction and Materials programs will be ranked next.

MAXIMUM TIME:                                    10 Minutes

 IMPOUND:                      YES