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A truss is an assembly of ''members'' such as beams, connected by ''nodes'', that creates a rigid structure. In engineering, a truss is a
structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A ...
that "consists of two-force members only, where the members are organized so that the assemblage as a whole behaves as a single object". A "two-force member" is a structural component where force is applied to only two points. Although this rigorous definition allows the members to have any shape connected in any stable configuration, trusses typically comprise five or more triangular units constructed with straight members whose ends are connected at joints referred to as ''
nodes In general, a node is a localized swelling (a "knot") or a point of intersection (a Vertex (graph theory), vertex). Node may refer to: In mathematics *Vertex (graph theory), a vertex in a mathematical graph *Node (autonomous system), behaviour fo ...
''. In this typical context, external forces and reactions to those forces are considered to act only at the nodes and result in forces in the members that are either
tensile In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through Spa ...
or
compressive In continuum mechanics, stress is a physical quantity that expresses the internal forces that neighbouring particles of a continuous material exert on each other, while deformation (mechanics)#Strain, strain is the measure of the deformation of ...
. For straight members, moments (
torque In physics and mechanics, torque is the rotational equivalent of linear force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the na ...

torque
s) are explicitly excluded because, and only because, all the joints in a truss are treated as
revolutes
revolutes
, as is necessary for the links to be two-force members. A planar truss is one where all members and nodes lie within a two-dimensional plane, while a space truss has members and nodes that extend into three dimensions. The top beams in a truss are called ''top chords'' and are typically in
compression Compression may refer to: Physical science *Compression (physics), size reduction due to forces *Compression member, a structural element such as a column *Compressibility, susceptibility to compression *Gas compression *Compression ratio, of a co ...
, the bottom beams are called ''bottom chords'', and are typically in
tension Tension may refer to: Science * Psychological stress * Tension (physics), a force related to the stretching of an object (the opposite of compression) * Tension (geology), a stress which stretches rocks in two opposite directions * Voltage or elect ...
. The interior beams are called ''webs'', and the areas inside the webs are called ''panels'', or from graphic statics (see Cremona diagram) ''polygons''.


Etymology

''Truss'' derives from the
Old French Old French (, , ; Modern French French ( or ) is a Romance language The Romance languages, less commonly Latin or Neo-Latin languages, are the modern languages that evolved from Vulgar Latin Vulgar Latin, also known as Popular o ...
word ''trousse'', from around 1200, which means "collection of things bound together". The term ''truss'' has often been used to describe any assembly of members such as a
cruck A cruck or crook frame is a curved timber Lumber, also known as timber, is wood Wood is a porous and fibrous structural tissue found in the stems and roots of tree In botany, a tree is a perennial plant with an elongated Pl ...
frame or a couple of rafters. One engineering definition is: "A truss is a single plane framework of individual structural member
ic
ic
connected at their ends of forms a series of triangle
ic
ic
to span a large distance".


Characteristics

A truss consists of typically (but not necessarily) straight members connected at joints, traditionally termed ''panel points''. Trusses are typically (but not necessarily) composed of triangles because of the structural stability of that shape and design. A triangle is the simplest geometric figure that will not change shape when the lengths of the sides are fixed. In comparison, both the angles and the lengths of a four-sided figure must be fixed for it to retain its shape. The joint at which a truss is designed to be supported is commonly referred to as the Munter Point.


Simple truss

The simplest form of a truss is one single triangle. This type of truss is seen in a framed roof consisting of
rafter Image:Photograph of the Roof Framing in the Bequet-Ribault House in Ste Genevieve MO.png, A ''double roof'' (using a Norman truss), ''common rafters'' supported by ''principal rafters'' (''top chords'' in this case) and an unusual extra layer of c ...
s and a ceiling
joist A joist is a horizontal structural member used in framing to span an open space, often between beams that subsequently transfer loads to vertical members. When incorporated into a floor A floor is the bottom surface of a room or vehicle. Flo ...

joist
, and in other mechanical structures such as
bicycles A bicycle, also called a bike or cycle, is a human-powered or motor-powered, pedal-driven, single-track vehicle A single-track vehicle is a vehicle that leaves a single ground track as it moves forward. Single-track vehicles usually have ...
and aircraft. Because of the stability of this shape and the methods of analysis used to calculate the forces within it, a truss composed entirely of triangles is known as a simple truss. However, a simple truss is often defined more restrictively by demanding that it can be constructed through successive addition of pairs of members, each connected to two existing joints and to each other to form a new joint, and this definition does not require a simple truss to comprise only triangles. The traditional diamond-shape bicycle frame, which utilizes two conjoined triangles, is an example of a simple truss.


Planar truss

A planar truss lies in a single
plane Plane or planes may refer to: * Airplane An airplane or aeroplane (informally plane) is a fixed-wing aircraft A fixed-wing aircraft is a heavier-than-air flying machine Early flying machines include all forms of aircraft studied ...
. Planar trusses are typically used in parallel to form roofs and bridges. The depth of a truss, or the height between the upper and lower chords, is what makes it an efficient structural form. A solid
girder A girder () is a support beam Beam may refer to: Streams of particles or energy *Light beam, or beam of light, a directional projection of light energy **Laser beam *Particle beam, a stream of charged or neutral particles **Charged particl ...
or
beam Beam may refer to: Streams of particles or energy *Light beam, or beam of light, a directional projection of light energy **Laser beam *Particle beam, a stream of charged or neutral particles **Charged particle beam, a spatially localized group ...
of equal strength would have substantial weight and material cost as compared to a truss. For a given span, a deeper truss will require less material in the chords and greater material in the verticals and diagonals. An optimum depth of the truss will maximize the efficiency.


Space frame truss

A
space frame In architecture and structural engineering, a space frame or space structure (3D truss) is a rigid, lightweight, truss-like structure constructed from interlocking struts in a geometry, geometric pattern. Space frames can be used to span large are ...

space frame
truss is a three-dimensional framework of members pinned at their ends. A
tetrahedron In , a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular , is a composed of four , six straight , and four . The tetrahedron is the simplest of all the ordinary and the only one that has fewer than 5 faces. The t ...

tetrahedron
shape is the simplest space truss, consisting of six members that meet at four joints. Large planar structures may be composed from tetrahedrons with common edges, and they are also employed in the base structures of large free-standing power line pylons. File:Tetrahedron.png, Simple tetrahedron File:SpaceFrame02.png, Diagram of a space frame such as used for a roof File:Pylon-gorai.jpg, This is a three-dimensional truss structure


Types

: ''For more truss types, see truss types used in bridges.'' There are two basic types of truss: * The pitched truss, or common truss, is characterized by its triangular shape. It is most often used for roof construction. Some common trusses are named according to their "web configuration". The chord size and web configuration are determined by span, load and spacing. * The parallel chord truss, or flat truss, gets its name from its parallel top and bottom chords. It is often used for floor construction. A combination of the two is a truncated truss, used in
hip In vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, ...
roof construction. A metal plate-connected wood truss is a roof or floor truss whose wood members are connected with metal connector plates.


Warren truss

Truss members form a series of equilateral triangles, alternating up and down.


Octet truss

Truss members are made up of all equivalent equilateral triangles. The minimum composition is two regular tetrahedrons along with an octahedron. They fill up three dimensional space in a variety of configurations.


Pratt truss

The Pratt truss was patented in 1844 by two
Boston Boston (, ), officially the City of Boston, is the capital city, capital and List of municipalities in Massachusetts, most populous city of the Commonwealth (U.S. state), Commonwealth of Massachusetts in the United States and 21st List of Unit ...

Boston
railway engineers, Caleb Pratt and his son Thomas Willis Pratt. The design uses vertical members for
compression Compression may refer to: Physical science *Compression (physics), size reduction due to forces *Compression member, a structural element such as a column *Compressibility, susceptibility to compression *Gas compression *Compression ratio, of a co ...
and diagonal members to respond to
tension Tension may refer to: Science * Psychological stress * Tension (physics), a force related to the stretching of an object (the opposite of compression) * Tension (geology), a stress which stretches rocks in two opposite directions * Voltage or elect ...
. The Pratt truss design remained popular as bridge designers switched from wood to iron, and from iron to steel. This continued popularity of the Pratt truss is probably due to the fact that the configuration of the members means that longer diagonal members are only in tension for gravity load effects. This allows these members to be used more efficiently, as slenderness effects related to
buckling In structural engineering Structural engineering is a sub-discipline of in which s are trained to design the 'bones and muscles' that create the form and shape of man-made structures. also must understand and calculate the , strength, and ...

buckling
under compression loads (which are compounded by the length of the member) will typically not control the design. Therefore, for given planar truss with a fixed depth, the Pratt configuration is usually the most efficient under static, vertical loading. The
Southern Pacific Railroad The Southern Pacific (or Espee from the railroad initials- SP) was an American Class I railroad Rail transport (also known as train transport) is a means of transferring passengers and goods on wheeled vehicle A vehicle (from la ...
bridge in Tempe,
Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak) is a U.S. state, state in the Southwestern United States, Southwestern region of the United States. It is also usually considered part of the Mountain States, Mountain states. It is th ...

Arizona
is a 393 meter (1,291 foot) long truss bridge built in 1912. The structure is composed of nine Pratt truss spans of varying lengths. The bridge is still in use today. The
Wright Flyer The ''Wright Flyer'' (the ''Kitty Hawk'',also known as ''Flyer'' I or 1903 ''Flyer'') made the first sustained flight by a manned heavier-than-air powered and controlled aircraft—an airplane—on 17 December, 1903. Invented and flown by W ...

Wright Flyer
used a Pratt truss in its wing construction, as the minimization of compression member lengths allowed for lower
aerodynamic drag In fluid dynamics In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids—liquids and gases. It has several subdisciplines, including ''aerodynamics'' (the study of air and other ...
.


Bowstring truss

Named for their shape, bowstring trusses were first used for arched
truss bridge A truss bridge is a bridge A bridge is a structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interacting or interrelated elements that ac ...

truss bridge
s, often confused with
tied-arch bridge A tied-arch bridge is an arch bridge An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the ...

tied-arch bridge
s. Thousands of bowstring trusses were used during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a global war A world war is "a war War is an intense armed conflict between states State may refer to: Arts, entertainment, and media Literatur ...
for holding up the curved roofs of aircraft hangars and other military buildings. Many variations exist in the arrangements of the members connecting the nodes of the upper arc with those of the lower, straight sequence of members, from nearly isosceles triangles to a variant of the Pratt truss.


King post truss

One of the simplest truss styles to implement, the king post consists of two angled supports leaning into a common vertical support. The queen post truss, sometimes ''queenpost'' or ''queenspost'', is similar to a king post truss in that the outer supports are angled towards the centre of the structure. The primary difference is the horizontal extension at the centre which relies on
beam Beam may refer to: Streams of particles or energy *Light beam, or beam of light, a directional projection of light energy **Laser beam *Particle beam, a stream of charged or neutral particles **Charged particle beam, a spatially localized group ...
action to provide mechanical stability. This truss style is only suitable for relatively short spans.


Lenticular truss

Lenticular trusses, patented in 1878 by William Douglas (although the Gaunless Bridge of 1823 was the first of the type), have the top and bottom chords of the truss arched, forming a lens shape. A lenticular pony truss bridge is a bridge design that involves a lenticular truss extending above and below the roadbed.


Town's lattice truss

American architect
Ithiel Town Ithiel Town (October 3, 1784 – June 13, 1844) was an American architect An architect is a person who plans, designs and oversees the construction of buildings. To practice architecture means to provide services in connection with the de ...
designed Town's Lattice Truss as an alternative to heavy-timber bridges. His design,
patented NPOV disputes from March 2021 A patent is a title A title is one or more words used before or after a person's name, in certain contexts. It may signify either generation, an official position, or a professional or academic qualification. In ...

patented
in 1820 and 1835, uses easy-to-handle planks arranged diagonally with short spaces in between them, to form a lattice.


Vierendeel truss

The Vierendeel truss is a structure where the members are not triangulated but form rectangular openings, and is a frame with fixed joints that are capable of transferring and resisting bending moments. As such, it does not fit the strict definition of a truss (since it contains non-two-force members): regular trusses comprise members that are commonly assumed to have pinned joints, with the implication that no moments exist at the jointed ends. This style of structure was named after the Belgian engineer Arthur Vierendeel,Vierendeel bruggen
/ref> who developed the design in 1896. Its use for bridges is rare due to higher costs compared to a triangulated truss. The utility of this type of structure in buildings is that a large amount of the exterior envelope remains unobstructed and can be used for
window A window is an opening in a wall A wall is a structure and a surface that defines an area; carries a load; provides security Security is freedom from, or resilience against, potential Potential generally refers to a currently unrealize ...

window
s and door openings. In some applications this is preferable to a braced-frame system, which would leave some areas obstructed by the diagonal braces.


Statics

A truss that is assumed to comprise members that are connected by means of pin joints, and which is supported at both ends by means of hinged joints and rollers, is described as being
statically determinateIn statics Statics is the branch of mechanics Mechanics (Ancient Greek, Greek: ) is the area of physics concerned with the motions of physical objects, more specifically the relationships among force, matter, and motion. Forces applied to obj ...
. Newton's Laws apply to the structure as a whole, as well as to each node or joint. In order for any node that may be subject to an external load or force to remain static in space, the following conditions must hold: the sums of all (horizontal and vertical) forces, as well as all moments acting about the node equal zero. Analysis of these conditions at each node yields the magnitude of the compression or tension forces. Trusses that are supported at more than two positions are said to be
statically indeterminateIn statics and structural mechanics, a structure is statically indeterminate when the static equilibrium equations - force and moment equilibrium conditions - are insufficient for determining the internal forces and Reaction (physics), reactions o ...

statically indeterminate
, and the application of Newton's Laws alone is not sufficient to determine the member forces. In order for a truss with pin-connected members to be stable, it does not need to be entirely composed of triangles. In mathematical terms, we have the following necessary condition for
stability Stability may refer to: Mathematics *Stability theory, the study of the stability of solutions to differential equations and dynamical systems **Asymptotic stability **Linear stability **Lyapunov stability **Orbital stability **Structural stability ...
of a simple truss: : m \ge 2j - r \qquad \qquad \mathrm where ''m'' is the total number of truss members, ''j'' is the total number of joints and ''r'' is the number of reactions (equal to 3 generally) in a 2-dimensional structure. When m=2j - 3, the truss is said to be ''statically determinate'', because the (''m''+3) internal member forces and support reactions can then be completely determined by 2''j''
equilibrium List of types of equilibrium, the condition of a system in which all competing influences are balanced, in a wide variety of contexts. Equilibrium may also refer to: Film and television * Equilibrium (film), ''Equilibrium'' (film), a 2002 scien ...
equations, once we know the external loads and the geometry of the truss. Given a certain number of joints, this is the minimum number of members, in the sense that if any member is taken out (or fails), then the truss as a whole fails. While the relation (a) is necessary, it is not sufficient for stability, which also depends on the truss geometry, support conditions and the load carrying capacity of the members. Some structures are built with more than this minimum number of truss members. Those structures may survive even when some of the members fail. Their member forces depend on the relative
stiffness Stiffness is the extent to which an object resists deformation Deformation can refer to: * Deformation (engineering), changes in an object's shape or form due to the application of a force or forces. ** Deformation (mechanics), such changes co ...
of the members, in addition to the equilibrium condition described.


Analysis

Because the forces in each of its two main girders are essentially planar, a truss is usually modeled as a two-dimensional plane frame. However if there are significant out-of-plane forces, the structure must be modeled as a three-dimensional space. The analysis of trusses often assumes that loads are applied to joints only and not at intermediate points along the members. The weight of the members is often insignificant compared to the applied loads and so is often omitted; alternatively, half of the weight of each member may be applied to its two end joints. Provided that the members are long and slender, the moments transmitted through the joints are negligible, and the junctions can be treated as "
hinge A hinge is a mechanical bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about a fixed axis of rotation: all other T ...

hinge
s" or "pin-joints". Under these simplifying assumptions, every member of the truss is then subjected to pure
compression Compression may refer to: Physical science *Compression (physics), size reduction due to forces *Compression member, a structural element such as a column *Compressibility, susceptibility to compression *Gas compression *Compression ratio, of a co ...
or pure
tension Tension may refer to: Science * Psychological stress * Tension (physics), a force related to the stretching of an object (the opposite of compression) * Tension (geology), a stress which stretches rocks in two opposite directions * Voltage or elect ...
forces – shear, bending moment, and other more-complex stresses are all practically zero. Trusses are physically stronger than other ways of arranging structural elements, because nearly every material can resist a much larger load in tension or compression than in shear, bending, torsion, or other kinds of force. These simplifications make trusses easier to analyze.
Structural analysis Structural analysis is the determination of the effects of load Load or LOAD may refer to: Aeronautics and transportation *Load factor (aeronautics), the ratio of the lift of an aircraft to its weight *Passenger load factor, the ratio of rev ...
of trusses of any type can readily be carried out using a matrix method such as the
direct stiffness methodAs one of the methods of structural analysis, the direct stiffness method, also known as the matrix stiffness method, is particularly suited for computer-automated analysis of complex structures including the statically indeterminate type. It is a ' ...
, the
flexibility method Stiffness is the extent to which an object resists deformation (mechanics), deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. Calculations ...
, or the
finite element The finite element method (FEM) is a widely used method for numerically solving differential equations In mathematics, a differential equation is an equation In mathematics Mathematics (from Ancient Greek, Greek: ) includes the stud ...
method.


Forces in members

Illustrated is a simple,
statically determinateIn statics Statics is the branch of mechanics Mechanics (Ancient Greek, Greek: ) is the area of physics concerned with the motions of physical objects, more specifically the relationships among force, matter, and motion. Forces applied to obj ...
flat truss with 9 joints and (2 x 9) − 3 = 15 members. External loads are concentrated in the outer joints. Since this is a
symmetrical Symmetry (from Greek συμμετρία ''symmetria'' "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more pre ...

symmetrical
truss with symmetrical vertical loads, the reactive forces at A and B are vertical, equal, and half the total load. The internal
force In physics, a force is an influence that can change the motion (physics), motion of an Physical object, object. A force can cause an object with mass to change its velocity (e.g. moving from a Newton's first law, state of rest), i.e., to acce ...

force
s in the members of the truss can be calculated in a variety of ways, including graphical methods: * Cremona diagram * Culmann diagram * Ritter analytical method ( method of sections)


Design of members

A truss can be thought of as a
beam Beam may refer to: Streams of particles or energy *Light beam, or beam of light, a directional projection of light energy **Laser beam *Particle beam, a stream of charged or neutral particles **Charged particle beam, a spatially localized group ...
where the web consists of a series of separate members instead of a continuous plate. In the truss, the lower horizontal member (the ''bottom chord'') and the upper horizontal member (the ''top chord'') carry
tension Tension may refer to: Science * Psychological stress * Tension (physics), a force related to the stretching of an object (the opposite of compression) * Tension (geology), a stress which stretches rocks in two opposite directions * Voltage or elect ...
and
compression Compression may refer to: Physical science *Compression (physics), size reduction due to forces *Compression member, a structural element such as a column *Compressibility, susceptibility to compression *Gas compression *Compression ratio, of a co ...
, fulfilling the same function as the
flange A flange is a protruded ridge, lip or rim, either external or internal, that serves to increase strength Physical strength *Physical strength, as in people or animals *Hysterical strength, extreme strength occurring when people are in life ...

flange
s of an
I-beam An I-beam, also known as H-beam (for universal column, UC), w-beam (for "wide flange"), universal beam (UB), rolled steel joist (RSJ), or double-T (especially in Polish Polish may refer to: * Anything from or related to Poland Polan ...
. Which chord carries tension and which carries compression depends on the overall direction of
bending In applied mechanics Applied mechanics is a branch of the physical science Physical science is a branch of natural science that studies abiotic component, non-living systems, in contrast to life science. It in turn has many branches, each re ...

bending
. In the truss pictured above right, the bottom chord is in tension, and the top chord in compression. The diagonal and vertical members form the ''truss web'', and carry the
shear stress Shear stress, often denoted by (Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its popu ...

shear stress
. Individually, they are also in tension and compression, the exact arrangement of forces is depending on the type of truss and again on the direction of bending. In the truss shown above right, the vertical members are in tension, and the diagonals are in compression. In addition to carrying the static forces, the members serve additional functions of stabilizing each other, preventing
buckling In structural engineering Structural engineering is a sub-discipline of in which s are trained to design the 'bones and muscles' that create the form and shape of man-made structures. also must understand and calculate the , strength, and ...

buckling
. In the adjacent picture, the top chord is prevented from buckling by the presence of bracing and by the stiffness of the web members. The inclusion of the elements shown is largely an engineering decision based upon economics, being a balance between the costs of raw materials, off-site fabrication, component transportation, on-site erection, the availability of machinery and the cost of labor. In other cases the appearance of the structure may take on greater importance and so influence the design decisions beyond mere matters of economics. Modern materials such as
prestressed concrete Prestressed concrete is a form of concrete Concrete is a composite material A composite material (also called a composition material or shortened to composite, which is the common name) is a material Material is a substance Substan ...

prestressed concrete
and fabrication methods, such as automated
welding Welding is a process that joins materials, usually s or s, by using high to melt the parts together and allowing them to cool, causing . Welding is distinct from lower temperature metal-joining techniques such as and , which do not the base ...

welding
, have significantly influenced the design of modern
bridge A bridge is a structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules t ...

bridge
s. Once the force on each member is known, the next step is to determine the
cross section Cross section may refer to: * Cross section (geometry), the intersection of a 3-dimensional body with a plane * Cross section (electronics), a common sample preparation technique in electronics * Cross section (geology), the intersection of a 3-dim ...
of the individual truss members. For members under tension the cross-sectional area ''A'' can be found using ''A'' = ''F'' × γ / σ''y'', where ''F'' is the force in the member, γ is a
safety factor In engineering, a factor of safety (FoS), also known as (and used interchangeably with) safety factor (SF), expresses how much stronger a system is than it needs to be for an intended load. Safety factors are often calculated using detailed analys ...
(typically 1.5 but depending on
building code A building code (also building control or building regulations) is a set of rules that specify the standards for constructed objects such as buildings and nonbuilding structures. Buildings must conform to the code to obtain planning permission, u ...
s) and σy is the yield
tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle tensi ...
of the steel used. The members under compression also have to be designed to be safe against buckling. The weight of a truss member depends directly on its cross section—that weight partially determines how strong the other members of the truss need to be. Giving one member a larger cross section than on a previous iteration requires giving other members a larger cross section as well, to hold the greater weight of the first member—one needs to go through another iteration to find exactly how much greater the other members need to be. Sometimes the designer goes through several iterations of the design process to converge on the "right" cross section for each member. On the other hand, reducing the size of one member from the previous iteration merely makes the other members have a larger (and more expensive) safety factor than is technically necessary, but doesn't ''require'' another iteration to find a buildable truss. The effect of the weight of the individual truss members in a large truss, such as a bridge, is usually insignificant compared to the force of the external loads.


Design of joints

After determining the minimum cross section of the members, the last step in the design of a truss would be detailing of the
bolted joint Bolted joints are one of the most common elements in construction Construction is a general term meaning the and to form , , or ,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Ox ...

bolted joint
s, e.g., involving shear stress of the bolt connections used in the joints. Based on the needs of the project, truss internal connections (joints) can be designed as rigid, semi rigid, or hinged. Rigid connections can allow transfer of bending moments leading to development of secondary bending moments in the members.


Applications


Post frame structures

Component connections are critical to the structural integrity of a framing system. In buildings with large, clearspan wood trusses, the most critical connections are those between the truss and its supports. In addition to gravity-induced forces (a.k.a. bearing loads), these connections must resist shear forces acting perpendicular to the plane of the truss and uplift forces due to wind. Depending upon overall building design, the connections may also be required to transfer bending moment. Wood posts enable the fabrication of strong, direct, yet inexpensive connections between large trusses and walls. Exact details for post-to-truss connections vary from designer to designer, and may be influenced by post type. Solid-sawn timber and glulam posts are generally notched to form a truss bearing surface. The truss is rested on the notches and bolted into place. A special plate/bracket may be added to increase connection load transfer capabilities. With mechanically-laminated posts, the truss may rest on a shortened outer-ply or on a shortened inner-ply. The later scenario places the bolts in double shear and is a very effective connection.


Gallery

File:Bank of china night.jpg, The Hong Kong Bank of China Tower has an externally visible truss structure File:HK HSBC Main Building 2008.jpg, The
HSBC Main Building, Hong Kong HSBC Main Building is a headquarters building of The Hongkong and Shanghai Banking Corporation HSBC (), officially known as The Hongkong and Shanghai Banking Corporation Limited (), is a wholly owned subsidiary of HSBC HSBC Holdings pl ...
has an externally visible truss structure File:Below Auckland Harbour Bridge Hossen27.jpg, Support structure under the
Auckland Harbour Bridge The Auckland Harbour Bridge is an eight-lane motorway bridge over the Waitematā Harbour in Auckland, New Zealand. It joins Saint Marys Bay, New Zealand, St Marys Bay on the Auckland city side with Northcote, New Zealand, Northcote on the Nor ...

Auckland Harbour Bridge
File:Auckland Harbour Bridge Watchman.jpg, The
Auckland Harbour Bridge The Auckland Harbour Bridge is an eight-lane motorway bridge over the Waitematā Harbour in Auckland, New Zealand. It joins Saint Marys Bay, New Zealand, St Marys Bay on the Auckland city side with Northcote, New Zealand, Northcote on the Nor ...

Auckland Harbour Bridge
seen from Watchman Island to its west File:The Little Belt Bridge (1935).jpeg, : a truss
bridge A bridge is a structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules t ...

bridge
in Denmark File:Bow-string-truss.jpg, Pre-fabricated steel bow string roof trusses built in 1942 for war department properties in Northern Australia File:Truss Dachstuhl.jpg, Roof truss in a side building of
Cluny Abbey Cluny Abbey (; , formerly also ''Cluni'' or ''Clugny''; ) is a former Benedictine The Benedictines, officially the Order of Saint Benedict ( la, Ordo Sancti Benedicti, abbreviated as OSB), are a monastic religious order of the Catholic Chur ...
, France File:Queen-post-truss.png, A section through a queen post
timber roof truss A timber roof truss is a structural framework of timbers designed to bridge the space above a room and to provide support for a roof. Truss A truss is an assembly of ''members'' such as Beam (structure), beams, connected by ''nodes'', that cre ...
File:Woodlands mall3 texas.jpg, A space truss carrying a floor in The Woodlands Mall File:Elledningsstolpe2 lund.jpg,
Electricity pylon A transmission tower or power tower (alternatively electricity pylon or variations) is a tall structure, usually a steel lattice tower, used to support an overhead power line. In electrical grids, they are generally used to carry high-voltag ...

Electricity pylon
File:Inside wboylston old stone church.jpg,
Timber roof truss A timber roof truss is a structural framework of timbers designed to bridge the space above a room and to provide support for a roof. Truss A truss is an assembly of ''members'' such as Beam (structure), beams, connected by ''nodes'', that cre ...
File:Temporary bridge made of Truss.jpg, Modern temporary bridge made of
Bailey bridge A Bailey bridge is a type of portable, pre-fabricated, truss A truss is an assembly of ''members'' such as beams, connected by ''nodes'', that creates a rigid structure. In engineering, a truss is a structure A structure is an arrangemen ...
truss panels in
Montreal Montreal ( ; officially Montréal, ) is the second-most populous city in Canada Canada is a country in the northern part of . Its extend from the to the and northward into the , covering , making it the world's . Its southern and w ...

Montreal
Québec Quebec ( , sometimes ; french: Québec, link=no )According to the Government of Canada, Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official ...

Québec
File:Three dimensional truss construction Unic Rotarex®.jpg, alt=Three dimensional truss construction, Three dimensional truss construction made b
Unic Rotarex®
File:Kratownica statycznie wyznaczalna - obciążenia.svg, Example of calculation truss forces made by program that use matrix Gauss solving method


See also

*
Lattice tower A lattice tower or truss tower is a freestanding vertical framework tower A tower is a tall structure, taller than it is wide, often by a significant factor. Towers are distinguished from masts by their lack of guy-wires and are therefore, ...
* Andreini tessellations, the only 28 ways to fill 3D space with trusses that have ''identical'' joints everywhere *
Brown truss A Brown truss is a type of bridge truss, used in covered bridges. It is noted for its economical use of materials and is named after the inventor, Josiah Brown Jr., of Buffalo, New York, Buffalo, New York (state), New York, who patented it July 7, ...
*
Geodesic dome A geodesic dome is a hemispherical of a sphere A sphere (from Greek language, Greek —, "globe, ball") is a Geometry, geometrical object in solid geometry, three-dimensional space that is the surface of a Ball (mathematics), ball (viz., anal ...

Geodesic dome
, a truss in the shape of a sphere *
Structural mechanics Image:Caterham7spaceframe-front.jpg, 220px, Tubular frame used in a competition car Structural engineering, Structural mechanics or Mechanics of structures is the computation of deformation (engineering), deformations, Deflection (engineering), defl ...
* Serrurier truss, a truss form used for telescopes * Stress: **
Compressive stress In long, slender structural elements — such as columns or truss Typical detail of a steel truss, which is considered as a revolute joint A truss is an assembly of beams or other elements that creates a rigid structure. In engineering, a tr ...
**
Tensile stress In continuum mechanics Continuum mechanics is a branch of mechanics that deals with the mechanical behavior of materials modeled as a continuous mass rather than as point particle, discrete particles. The French mathematician Augustin-Louis ...
*
Structural steel Structural steel is a category of steel Steel is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, ...
* , a truss where no compression member touches any other compression member *
Truss rod The truss rod is component of a guitar The guitar is a fretted musical instrument that typically has six string instrument, strings. It is held flat against the player's body and played by strumming or Plucked string instrument, plucking the st ...
, a
guitar The guitar is a fretted musical instrument that typically has six string instrument, strings. It is held flat against the player's body and played by strumming or Plucked string instrument, plucking the strings with the dominant hand, while sim ...

guitar
part


References


External links

{{Authority control Airship technology Architectural elements Bridge components Mechanics Structural system