Forces on Basic Bridge Types


Forces on a Beam Bridge

Forces on a Truss  


When something pushes down on the beam, the beam bends. Its top edge is pushed together, and its bottom edge is pulled apart.


Every bar in this cantilever bridge experiences either a pushing or pulling force. The bars rarely bend. This is why cantilever bridges can span farther than beam bridges.

Suspension Bridge: Forces

Arch Bridge: Forces

In all suspension bridges, the roadway hangs from massive steel cables, which are draped over two towers and secured into solid concrete blocks, called anchorages, on both ends of the bridge. The cars push down on the roadway, but because the roadway is suspended, the cables transfer the load into compression in the two towers. The two towers support most of the bridge's weight.

The arch is squeezed together, and this squeezing force is carried outward along the curve to the supports at each end. The supports, called abutments, push back on the arch and prevent the ends of the arch from spreading apart.

  • other bridge sites


Resources on bridges from PBS including...

In addition, a list of links to information about some of the world's biggest and best bridges is available.

  • NOVA: Superbridge
    The NOVA program chronicles the building of the state-of-the-art Clark Bridge over the Mississippi River.
  • How Stuff Works
    In this edition of HowStuffWorks, they look at the three major types of bridges so that we can understand how each one works.
  • Bridge Construction
    A High School step by step guide, including photos, of how to design and build a bridge.
  • Truss Bridge Design
    Wordy article explaining the history and principles of truss bridge design. Several good diagrams.
  • Bridge Building
    Great site from the Deutsches Museum. Great articles/pictures explaining Arch, Beam, Suspension and Cable-Stayed Bridges.



California Geological Survey - Online Maps and Data

MAGIC: Map and Geographic Information Center

California 30-minute Topographic maps

Geography - Search Results

GlobeXplorer ImageAtlas

Satellite Imagery

7.5 Minute DEMs of California


TopoZone - The Web s Topographic Map and more!

Maps and Mapping Resources

Microsoft TerraServer Imagery

MapQuest.Com Maps, Directions and More


The BridgeSite - Fun and Learning

BUILDING BIG: All About Bridges

BUILDING BIG: Databank: Search

Build It & Bust It: A Webside Construction Zone

The Toothpick Bridge




  • Bridge Statistics

Bridges Project - Rice University - Awesome searchable database of bridge information

Bureau of Transporation Statistics (US). Huge databases of transporation data and research papers (check out TRIS).

Steel Bridges of the World and Other Statistics

US Bridge Inventory Statistics - Better Roads Magazine

Major Bridge Statistics - Organized by bridge type


  • Check out these bridges...
Akashi Kaikyo Bridge
Brooklyn Bridge
Charles River Bridge
Chesapeake Bay Bridge-Tunnel
Firth of Forth Bridge
Garabit Viaduct
George P. Coleman Bridge
Golden Gate Bridge
Iron Bridge
New River Gorge Bridge
Sunshine Skyway Bridge
Tacoma Narrows Bridge
Tower Bridge


Bridge Designer (On-line Free)
This program allows you to design and test trusses. Trusses are composed of straight members connected at their ends by hinged connections to form a stable configuration.

West Point Bridge Designer (Free - PC only)
This software will introduce you to engineering through an authentic, hands-on design experience. WPBD 2003 provides you with the tools to model, test, and optimize a steel highway bridge, based on realistic specifications, constraints, and performance criteria.

CyberBee: Fun with Science: Bridges, Bubbles, and Boulders

Bridge Building

BUILDING BIG: Webography: Bridges
Mrs. Herook, Building Bridges Resource Page -



Copyright 2005 -  S. B. EglI