A lattice girder is a girder

Girder

A girder is a support beam used in construction. Girders often have an I-beam cross section for strength, but may also have a box shape, Z shape or other forms. Girder is the term used to denote the main horizontal support of a structure which supports smaller beams...

 where the flange

Flange

A flange is an external or internal ridge, or rim , for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel...

s are connected by a lattice

Latticework

Latticework is a framework consisting of a criss-crossed pattern of strips of building material, typically wood or metal. The design is created by crossing the strips to form a network...

 web. This type of design has been supplanted in modern construction with welded

Welding

Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...

 or bolted plate girders, which use more material but have lower fabrication and maintenance costs. The lattice girder was used prior to the development of larger rolled steel plates.

The term is also sometimes used to refer to a structural member commonly made using a combination of structural sections connected with diagonal lacing. This member is more correctly referred to as a laced strut or laced tie, as it normally resists axial compression (strut

Strut

A strut is a structural component designed to resist longitudinal compression. Struts provide outwards-facing support in their lengthwise direction, which can be used to keep two other components separate, performing the opposite function of a tie...

) or axial tension

Tension (mechanics)

In physics, tension is the magnitude of the pulling force exerted by a string, cable, chain, or similar object on another object. It is the opposite of compression. As tension is the magnitude of a force, it is measured in newtons and is always measured parallel to the string on which it applies...

 (tie

Tie (engineering)

A tie, structural tie, connector, or structural connector is a structural component designed to resist tension. It is the opposite of a strut, which is designed to resist compression. Ties are generally made of galvanized steel...

); the lattice girder, like any girder, primarily resists bending

Bending

In engineering mechanics, bending characterizes the behavior of a slender structural element subjected to an external load applied perpendicularly to a longitudinal axis of the element. The structural element is assumed to be such that at least one of its dimensions is a small fraction, typically...

.

The component sections may typically include metal beams, channel and angle sections, with the lacing elements either metal plate strips, or angle sections. The lacing elements are typically attached using either hot rivets or threaded locator bolts. As with lattice girders, laced struts and ties have generally been supplanted by hollow box sections, which are more economic with modern technology. In some case seismic retrofit

Seismic retrofit

Seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. With better understanding of seismic demand on structures and with our recent experiences with large earthquakes near urban centers,...

 modifications replace riveted lacing with plates bolted in place.

Some structures employing lattice girders

• Runcorn Railway Bridge
  Runcorn Railway Bridge
  The Runcorn Railway Bridge, which is also known as the Ethelfleda Bridge or the Britannia Bridge, crosses the River Mersey at Runcorn Gap from Runcorn to Widnes in Cheshire, England. It was built for the London and North Western Railway to a design by William Baker, chief engineer of the railway...
  
  
• Kew Railway Bridge
• Dowery Dell
  Dowery Dell
  Dowery Dell, near Hunnington in Worcestershire, was notable for a cast iron railway viaduct that carried the Halesowen to Longbridge railway until it was dismantled in 1964....
  
   Viaduct, demolished 1964
• Bennerley Viaduct
  Bennerley Viaduct
  Bennerley Viaduct is a disused railway viaduct spanning the Erewash Valley between Awsworth in Nottinghamshire and Ilkeston in Derbyshire.- Origins :...
  
  

Some structures employing laced struts or ties

• The Eiffel Tower
  Eiffel Tower
  The Eiffel Tower is a puddle iron lattice tower located on the Champ de Mars in Paris. Built in 1889, it has become both a global icon of France and one of the most recognizable structures in the world...
  
  
• The obsolescent eastern span of the San Francisco – Oakland Bay Bridge. The western span has been retrofitted with bolted plates replacing the lacing for added strength.
• The internal structure of the Statue of Liberty
  Statue of Liberty
  The Statue of Liberty is a colossal neoclassical sculpture on Liberty Island in New York Harbor, designed by Frédéric Bartholdi and dedicated on October 28, 1886...
  
  
• The sides of the Cape Fear Memorial Bridge
  Cape Fear Memorial Bridge
  The Cape Fear Memorial Bridge is a steel vertical-lift bridge in North Carolina. It carries U.S. Route 17 Business, U.S. Route 76, and U.S. Route 421 across the Cape Fear River between Brunswick County and New Hanover County. It also carried U.S. Route 74 until that designation was shifted to the...
  
  

See also

• Lattice truss bridge—an extension of the concept to form a deep truss
  Truss
  In architecture and structural engineering, a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes. External forces and reactions to those forces are considered to act only at the nodes and result in...
  
  .
• Hares Hill Road Bridge
  Hares Hill Road Bridge
  The Hares Hill Road Bridge is a single-span, wrought iron, arched-shaped lattice girder bridge. It was built in 1869 in Chester County, Pennsylvania by Moseley Iron Bridge and Roof Company and is the only known surviving example of this kind. The bridge crosses French Creek, a Scenic River, and...