Types Of Truss Bridges

Truss bridges are probably one of the oldest and the most common types of bridges in the world. Basically a truss bridge is composed of truss which is straight lined structure made up of small triangular units.

The elements used in the making of the truss bridge are connected through compression stress, tension or sometimes all of these factors.

On the basis of designs and the elements used for the making of the bridge, the truss bridges are classified into following types:

Allan Truss Bridge

The Allan truss bridge is named after Percy Allan, a famous Australian architect and engineer who designed the bridge.

His design consists of vertical and diagonal arrangements of trusses which are were originally composed of steel.

Today many of the bridges based on Percy Allan’s design are composed of iron bark or even timber to reduce the cost.

The Hampden Bridge in New South Wales Australia was the first bridge to be built on Percy Allan’s design.

Howe truss bridge is a basic design of truss bridges based on which many engineers gave modified designs for many other famous truss bridges of the world.

It has a simple design which consists of diagonal and vertical trusses. The diagonal trusses move upwards and slope towards the centre of the bridge. The vertical members of the truss are in tension while the members of the diagonal truss are in compression.

This bridge was first designed by William Howe in 1840. Jay Bridge in New York and Sandy creek covered bridge in Jefferson County, Missouri are to bridges based on Howe’s design.

The design of the Pratt truss is bridge is the opposite of the Howe Truss Bridge. Although they too like the Howe truss have vertical and diagonal members, the major difference between the two is that in the Pratt Truss Bridge the Diagonal slope down towards the centre.

This bridge was invented by Thomas and Caleb Pratt in1844. Originally this bridge was built with iron but not wood is also used in its making. This bridge can be extended up to 250 feet therefore it is commonly used as a railway bridge.

The Bailey bridge is basically built for the military purposes.

It built at the extension of 60m and can bear the weight of heavy loaded ranks.

The design of these bridges is simple and may only consist of trusses stacked vertically.

The construction of the bridge does not require heavy machinery or tools for its construction.

The K truss bridges have a complex and a complicated design and are believed to the hardest bridges to build.

As the name suggests the shape of the bridge is in the form of the letter K. The members are oriented in a way that the vertical and the oblique members are shaped in letter K in each panel.

The bowstring Arch truss or the Tied Arch Bridge was designed in 1840 by Squire Whipple. The bridge is composed of Thrust Arches which transform their vertical load along the arc of the arch.

At the ends of the arc, the thrust arches are resolved into two components a vertical and a horizontal thrust.

The vertical thrust is usually equal to the weight and load of the bridge section while the horizontal typically is taken down to the ground. If the arch is bowstring the horizontal thrust is taken to the opposite side of the arch by a chord.

The load which is faced vertically by the thrust arches are usually transferred along the path of the arc.

The king post truss which is also known as the ‘crown post’ truss bridge is probably the simplest type of truss bridges.

It simply consists of a single vertical support on which two angled trusses lean to.

It is also the oldest or most probably the first kind of truss bridges ever made. They were common during the medieval times.

Lattice truss bridges are another type of simple truss bridges which are comparatively easier to construct than the other types of bridges.

They are usually built of iron, steel or wood and are common in small towns and cities.