Truss Design - Truss Types and Benefits
In its most basic form, a truss is a structure that is taking advantage of
the inherent stability and the weight distribution of triangle. The web of
such triangles can be joined, and resulting effect causes stress to be
evenly distributed across the entire structure that can be dramatically
more lightweight than the walls created from strong materials.
this approach, enormous weight and stress can be safely held by the
load-bearing beams, walls or ground, even when outside forces such as the
wind (noticeably present truss structures placed on tall buildings) or
vibrations (swaying of bridges due to traffic or the wind). Those uneven
forces are safely distributed across entire truss structure. Ever since
first truss structures became first used in Ancient Egypt and more commonly
found in the architectural project all across Roman Empire, they became an
integral part of modern architecture on which many modern structures are
built, including homes for billions of people all around the world.
Truss is a framework structure that distributes the load by taking advantage of the inherent stability of a triangle.
Trusses are an integral part of modern architecture and building. Since
they can carry so much weight by themselves, their presence enables
builders to achieve maximal economy of materials, easily cover large
distances with simple truss meshes, evenly take the load from heavy
structures, easily access entire structure, save on expensive materials,
and build structures that are accessible for maintenance after initial
Wooden trusses are most common and can be found in the
housing industry as one of the most common architectural designs for
carrying roof or ceiling structures. Trusses made from wood are considered
incredibly useful because they can be easily constructed quickly on site,
with very little cheap and accessible material needed to create the
structure that can carry large weight load. Wood trusses can be used to
span distance of up to 35 meters, which is more than enough for the
creation of very durable and long-lasting bridges.
Truss enables the creation of light structures that can span large distances and endure very heavy loads.
Basic types of truss:
– A truss created from the single triangle, often used for building lighter
roofs, supporting ceiling structures, or providing strength to the metal
frame of bicycles (the core of every modern bicycle design is a single
triangle between seating position, pedals and handles, and additional
triangle that connects core triangle to the rear wheel) and many other
lightweight structures (like airplanes).
– By connecting more truss triangles, we get planar structures that share
the load that is placed on them. Most commonly, the planar design consists
of the single repeating pattern and are most commonly used fro building of
roofs and bridges.
– Truss designs can also be made in 3 dimensions, with tetrahedron being
the most simple and commonly used of space truss. It consists of six
distinct elements that that meat at four joints. The mesh of space frame
elements is most commonly used in the construction of “floors” built on top
of just a few load bearing points that need to carry very large weight on
top of them.
All truss structures can be placed into two basic categories of the common
truss (created from repeated triangles) and flat truss (in which custom
designed arrangement of triangles is placed between parallel top and bottom
chords). However, over the last two thousand years, engineers and
architects have devised dozens upon dozens of truss design approaches that
are today used in various structures ranging from house floors and ceilings
to the bridges, hangars, buildings, infrastructure objects and
transportation vehicles from simple bikes to space rockets. Most popular
truss types used today in modern construction are:
– Created as an evolution of Howe trusses (where diagonals slope toward
the center of the bridge), first bridge of this design was created in
August of 1894 in Australia by civil engineer Percy Allan who during
his career designed over 580 bridges. Alan truss designs multiply the
number of Howe trusses, enabling the creation of much longer bridges
that are supported by one or more support points.
– Originally designed during WWII for easy assembly on site during
military engagements using pre-fabricated parts. Today, timber and
steel versions of these bridges are used for used for carrying
pedestrians, road and rail vehicles.
– A variation of Pratt trusses that utilizes an additional bracing in the
lower sections of the bridge truss network. It is used mostly for
carrying rail transport.
– Very rare truss type that survives today in the only bridge of its
design left standing. Bollman Truss Railroad Bridge in Savage, Maryland
features revolutionary all-metal design.
– Patented in 1841, bowstring is one of the most popular truss designs
for smaller truss bridges.
– Very popular truss design that features diagonal cross compression
members that are connected to the horizontal top and bottom stringers.
They are mostly used for bridges made from wood, most notably covered
Burr arch truss
– Another truss design that is used a lot in the creation of covered
bridges. In addition to the traditional planar triangle truss design,
it also features an arch that gives entire structure additional
strength and rigidity.
– A truss network that is placed on the cantilevered bridges, whose
main decks are heavily anchored from the central vertical spars. Most
bridges of this design have trusses placed both above (where
construction is placed under compression) and below (where the bridge
is placed under tension) the main decks of the bridge.
- A unique looking truss design that is placed only under the decks of
bridges (usually intended for carrying train or road vehicle
transport). At the time of its creation in 1860, a Fink truss enabled
the creation of the longest all-iron bridges in the world.
- A very popular truss type in which features triage diagonals that
slope upward toward the center. Many smaller bridges and architectural
solutions for homes feature this simple design.
– Bridge type that features several types of triangles, who in the
center of the structure from the normal and inverted character of “K”
– An evolution of the easiest to make “Simple” truss, which is enhanced
with a single vertical support line.
– Similar as Kingpost truss, but with added horizontal extension that
separates two diagonal outer supports.
– Another very simple truss design. It uses a single tall triangle that
is reinforced with two inward-facing triangles.
– This truss type demands use of a large number of small and closely
spaced diagonal elements that form a lattice. This design is usually
used for the creation of lightweight structures (made from wood, iron
or steel) such as smaller bridges or hangars.
– Design of this truss type consists from a big lens-shape truss that
is elevated above the main deck of the bridge. This lens is separated
into two parts, with both upper and lower arches having their network
of trusses. If the deck of the bridge is placed in the middle of the
lens, then that bridge is called lenticular pony truss.
– Based on the Howe Truss, but made exclusively from wood. The longest
surviving bridge of this type is Eldean Covered Bridge north of Troy,
Ohio. Built in 1860, this bridge spans the distance of 68 using one
central anchor point.
– This is a very popular truss design that instead of the smooth arch
features rigged arch that directly connects the edges of the truss
mesh. It closely resembles bowstring arch truss. It is also known as
camelback truss design.
– This is a hybrid of Pegram truss designs, with the most notable
difference is that upper chords are all of the equal lengths, and lower
ones are longer.
Pennsylvania (Petit) truss
– Truss type whose lower section of the mesh are additionally
reinforced with additional triangles.
– Very popular truss design where diagonal supports slope down toward
center (while in Howe trusses are pointing in the opposite direction).
This design enables the creation of structures that have spans of 76
meters between anchor points. Bridges with this design were very
commonly made between a middle of 19th and early 20th century.
– A rare variation of Pratt and Howe truss design.
- An arch bridge whose inverse arch is built from the truss mesh below
the main deck of the bridge. Vertical supports connect this arch to the
decking. It can be used for the creation of medium-sized bridges that
can even carry heavy railroad transport.
– A truss design that does not uses regular triangular elements, but
rigid rectangular openings and strong reinforcements from other
elements and connectors. Today it can most commonly be found only in
Belgium. Only one movable bridge of this design exists today.
– A very simple truss design that consists of two parallel chords and
equally sized triangles placed in between. This effective design is
popular not only in construction but also in production countless other
machines and systems. For example, early two-winged airplanes used
lightweight Warren truss mesh to reinforce the structure of the wings.
– Another variation of the Pratt truss design, but made with vertical
bars that are held together with an array of diagonal members
(lightweight and put at a shallower angle that enables them to cross
one or more vertical bars) designed to work together to alleviate
tension from the rest of the structure.