www.bridgeweb.com
www.faculty.fairfield.edu/jmac/rs/bridges.htm
www.brantacan.co.uk/artofbridges.htm
http://www.42explore.com/bridge.htm
www.idahoptv.org/buildingbig/activities.html
www.aviewoncities.com/nyc/brooklynbridge.htm
www.pghbridges.com/basics.htm
www.technologystudent.com/struct1/struindex.htm
www.hulcher.com/contractor-services/engineering-maintenance-of-way/railroad-bridge-maintenance.asp