Paper Truss Bridge MESA Day 2010 Competition

Intro To Truss Bridges A truss bridge uses a triangle based lattice work design to add rigidity to the supporting beams, greatly increasing their ability to dissipate compression and tension. Once the beam begins to compress, the force is dissipated through the truss.

How Truss Bridges Work In a beam bridge, the top of the beam has the most compression, the bottom the most tension, and the middle very little of either. If you look at the truss as a single beam, the majority of your material is at the top and bottom, creating more rigidity where it takes on the most force.

How Truss Bridges Work Additionally, the use of triangles within the truss allows it to dissipate the load throughout the truss work.

Types of Truss Bridges 3 main types of truss bridges Through Truss – traffic travels through the lattice work structure Deck Truss – traffic travels above the lattice work structure Pony Truss – traffic travels between the lattice work structure

Popular Designs WARREN TRUSS The Warren truss is perhaps the most common truss for both simple and continuous trusses. For smaller spans, no vertical members are used lending the structure a simple look (illustration #1.) For longer spans vertical members are added providing extra strength (illustration #2.) 1 2 Matsuo Bridge Company - http://www.matsuo-bridge.co.jp/english/bridges/basics/truss.shtm

Popular Designs PRATT TRUSS The Pratt truss is identified by its diagonal members which, except for the very end ones, all slant down and in toward the center of the span. Except for those diagonal members near the center, all the diagonal members are subject to tension forces only while the shorter vertical members handle the compressive forces. This allows for thinner diagonal members resulting in a more economic design. Matsuo Bridge Company - http://www.matsuo-bridge.co.jp/english/bridges/basics/truss.shtm

Popular Designs HOWE TRUSS The Howe truss Is the opposite of the Pratt truss. The diagonal members face in the opposite direction and handle compressive forces. Matsuo Bridge Company - http://www.matsuo-bridge.co.jp/english/bridges/basics/truss.shtm

Competition Resources Bridges – a very comprehensive site (http://www.teachers.ash.org.au/jmresources/structures/bridges.html) Building Big - Bridges (http://www.pbs.org/wgbh/buildingbig/bridge/index.html ) Westpoint Bridge Designer Software (http://bridgecontest.usma.edu/ ) Johns Hopkins Bridge Designer (http://www.jhu.edu/virtlab/bridge/truss.htm)