1. Bridge Design Bridges will be evaluated on: o Efficiency: Mass held by mass of bridge o Aesthetics: Cool factor Consider beam or truss o Truss usually stronger o Truss usually more aesthetic

2. Design Requirements Scale: 1 cm = 1 m Superstructure must be above roadway Substructure cannot exceed 4 cm (2 m) below roadbed Most efficient bridge wins bid Best aesthetic design/efficient bridge wins bid * For WPBD Only SpecificationActual SizeWPBD size Road Height*6 cm6 m Height3-9 cm3-9 m Width9cm +/- 1 cm 9 m +/-.1 m Span40 cm +/- 1 cm 40 m +/-.1 m SubstructureMin. 5 cm shorter than span of bridge Min. 5 m shorter than span of bridge SubstructureCannot exceed 4 cm below roadbed Cannot exceed 4 m below roadbed

3. Beam Sizes To closely match our materials for construction (1/8 x 1/8 balsa), use the following: Carbon steel Hollow tube 240mm x 240mm x 12mm Caveat to above: You may laminate 2 beams of your choice o Laminates can be made of 2 strips of balsa o Laminate cannot be cut into smaller pieces and used.

4. Bridge Example Substructure must be 1.25 m/cm inside end supports End Support 1.25 m/cm