structural engineering Structural engineering is a sub-discipline of civil engineering in which structural engineers are trained to design the 'bones and joints' that create the form and shape of human-made Structure#Load-bearing, structures. Structural engineers also ...

, a Warren truss or equilateral truss is a type of

truss A truss is an assembly of ''members'' such as Beam (structure), beams, connected by ''nodes'', that creates a rigid structure. In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so ...

employing a weight-saving design based upon

equilateral triangles An equilateral triangle is a triangle in which all three sides have the same length, and all three angles are equal. Because of these properties, the equilateral triangle is a regular polygon, occasionally known as the regular triangle. It is the ...

. It is named after the British engineer James Warren, who patented it in 1848.

Origins

It was patented in 1848 by its designers James Warren and Willoughby Theobald Monzani.

Truss

The Warren truss consists of longitudinal members joined only by angled cross-members, forming alternately inverted

equilateral triangle An equilateral triangle is a triangle in which all three sides have the same length, and all three angles are equal. Because of these properties, the equilateral triangle is a regular polygon, occasionally known as the regular triangle. It is the ...

-shaped spaces along its length. This gives a pure truss: each individual

strut A strut is a structural component commonly found in engineering, aeronautics, architecture and anatomy. Struts generally work by resisting longitudinal compression, but they may also serve in tension. A stay is sometimes used as a synonym for ...

, beam, or tie is only subject to tension or compression forces, there are no bending or torsional forces on them. Loads on the diagonals alternate between compression and tension (approaching the centre), with no vertical elements, while elements near the centre must support both tension and compression in response to live loads. This configuration combines strength with economy of materials and can therefore be relatively light. The girders being of equal length, it is ideal for use in prefabricated modular bridges. It is an improvement over the Neville truss in which the elements form

isosceles triangle In geometry, an isosceles triangle () is a triangle that has two Edge (geometry), sides of equal length and two angles of equal measure. Sometimes it is specified as having ''exactly'' two sides of equal length, and sometimes as having ''at le ...

s. A variant of the Warren truss has additional vertical members within the triangles. These are used when the lengths of the upper horizontal members would otherwise become so long as to present a risk of

buckling In structural engineering, buckling is the sudden change in shape (Deformation (engineering), deformation) of a structural component under Structural load, load, such as the bowing of a column under Compression (physics), compression or the wrin ...

These verticals do not carry a large proportion of the truss loads; they act mostly to stabilise the horizontal members against breaking down.

Bridges

Architecture

The Warren truss is a prominent structural feature in hundreds of hastily constructed aircraft hangars in WW2. In the early parts of the war, the British and Canadian government formed an agreement known as the

British Commonwealth Air Training Plan The British Commonwealth Air Training Plan (BCATP), often referred to as simply "The Plan", was a large-scale multinational military aircrew training program created by the United Kingdom, Canada, Australia and New Zealand during the Second Wo ...

which used newly constructed airbases in Canada to train aircrew needed to sustain emerging air forces. Hundreds of airfields, aprons, taxiways and ground installations were constructed all across Canada. Two characteristic features were a triangle runway layout and hangars built from virgin British Columbia timbers with Warren truss configuration roofs. Many still remain in service.

Aircraft

Warren truss construction has also been used in

airframe The mechanical structure of an aircraft is known as the airframe. This structure is typically considered to include the fuselage, undercarriage, empennage and wings, and excludes the propulsion system. Airframe design is a field of aeros ...

design and construction, for substantial numbers of aircraft designs. An early use was for the interplane wing struts on some biplanes. The Italian World War I Ansaldo SVA series of fast reconnaissance biplanes were among the fastest aircraft of their era, while the Handley Page H.P.42 was a successful

airliner An airliner is a type of airplane for transporting passengers and air cargo. Such aircraft are most often operated by airlines. The modern and most common variant of the airliner is a long, tube shaped, and jet powered aircraft. The largest ...

of the late 1920s and the Fiat CR.42 Falco ''Falco'' fighter remained in service until World War II. The Warren truss is also sometimes used for

fuselage The fuselage (; from the French language, French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds Aircrew, crew, passengers, or cargo. In single-engine aircraft, it will usually contain an Aircraft engine, engine as wel ...

frames, such as in the

Piper J-3 Cub The Piper J-3 Cub is an American light aircraft that was built between 1938 and 1947 by Piper Aircraft. The aircraft has a simple, lightweight design which gives it good low-speed handling properties and short-field performance. The Cub is Pi ...

and

Hawker Hurricane The Hawker Hurricane is a British single-seat fighter aircraft of the 1930s–40s which was designed and predominantly built by Hawker Aircraft Ltd. for service with the Royal Air Force (RAF). It was overshadowed in the public consciousness by ...

Notes

Explanatory notes

Citations

{{Reflist, refs= {{Cite web , title=The Warren Truss , website=Structure , date=July 2015 , author= Frank Griggs, Jr. , url=http://www.structuremag.org/?p=8715 {{Cite web , title=Warren Truss , website=Garrett's Bridges , url=https://www.garrettsbridges.com/design/warren-truss/ {{Cite book , title=Brunel in South Wales , first=Stephen K. , last=Jones , volume=III: ''Links with Leviathans'' , year=2009 , publisher=The History Press , location=Stroud , isbn=9780752449128 , pages=20–21 {{Cite book , title=Bridges of Britain , first=Eric , last=de Maré , year=1975 , orig-year=1954 , publisher=Batsford , isbn=0-7134-2925-9 , pages=86–87 Trusses