Civil Engineering

Bridge Building Contest

 

The Basics:

 

            Construct a truss bridge from balsa wood or bass wood to carry a load at one of the quarter points.

 

Design Rules:

 

  1. The end piers (bearing supports) will be 24” apart (inside) and will be 1.5” wide. (See the illustration.) It is recommended that you allow at least 1/2” to extend onto the pier.

 

  1. The overall dimensions for the bridge must not exceed 7.00” in height and 6.00” in width. It must allow the unobstructed passage of a 3.00” high by 5.00” wide block. (See the illustration.)

 

  1. No individual truss member may exceed 1/8”x 1/8” in cross-section except for the deck (see below). Except at the bearing surfaces (the two ends) you may not laminate pieces to make member cross-sections that exceed 1/8”x 1/8”. The connections between truss members must be made with glue (type and brand of your choice). Do not use gusset plates.

 

  1. The bridge must have a deck (road surface). The deck material must not exceed 1/16” in thickness and must have three 1/4” holes drilled at the quarter points. A slight variation in the hole placement can be made in order to miss substructure (below the deck) members.

 

  1. The substructure may not extend more than 1.00” below the bottom of the deck.

 

The Competition:

 

Each bridge will be loaded to destruction. The winner will be determined by the largest ratio:

 

LOAD AT FAILURE

WEIGHT OF TRUSS

Get a copy of “Something about Trusses” for construction hints from your instructor.