Types Of Truss Bridges

In this article, we are going to look in brief at what are trusses, types of truss bridges, different truss designs, and Howe Truss bridges.

First thing to remember that a very prominent phenomenon in structural engineering is a truss. So, what is a truss? A truss is a structure that encompasses a collection of elements joined at nodes or pin joints. It is a triangulated composition of members that are joined and structured to incur only axial force. They apply the forces only at either end of the member. This results in either a tension force or compression. Hence, these are two-force members. Trusses are usually used in designing a bridge. They have the ability to span long distances efficiently.

It is also crucial to note that a truss member only incurs axial force, in opposition to a frame member. The frame member generally incurs the combination of axial, shear, and bending forces.

Engineers conceive a truss as a web of triangular structures connected to each other to ensure a uniform distribution of weight. This also enables the handling of bartering compression and tension without bending or shearing. The triangular structure is steady in a geometrical sense, compared to a four or more-sided shape that requisites the corner joints to be fixed to prevent shearing.

Some assumptions are made during the process of designing. The construction of a truss must comply with designing assumptions. These assumptions are:

1. Truss members only carry the axial forces
2. The connecting points of the members, or the nodes, are designed to be pinned joints to avoid transferring moments to the truss
3. All reactions and external loads act only on the nodes
4. The truss should be on a plane

WHAT ARE THE USES OF TRUSS BRIDGES?

Usually, trusses are used to:

1. Acquire lengthy spans
2. Reduce the weight of a structure
3. Provide reduction in deflection
4. Support or aid heavy loads

Typically, three key elements are used to make trusses. They are as follows:

1. A chord at the top in compression.
2. A chord at the bottom in tension
3. A bracing situated between the bottom and top chords

Resistance to overall bending is fundamental in this structure. The top and bottom chords offer resistance to forces of compression and tension. This resists overall bending.

The efficiency of trusses lies in less necessity of material to support loads compared to solid beams. The general efficiency is measured by the utilization of less material within the chords and more material in bracing elements.

WHAT ARE THE TYPES OF TRUSSES?

Here are given different types of trusses:

1. Simple truss
2. Planar truss
3. Space frame truss

Let us explore each of them thoroughly.

1. SIMPLE TRUSS

Builders commonly use this type of truss in the construction of roofs. Simple Truss is the simplest form of truss and shows a single triangular truss structure.

2. PLANAR TRUSS

This is a two-dimensional truss. If the nodes and all members are built on a planar surface, then this type of truss is a planar truss.

3. SPACE FRAME TRUSS

In contrast to the previously mentioned planar truss, the members and nodes in a space frame truss are in a three-dimensional domain. Some daily life examples of space frame truss types are the telecom towers or other electricity towers that we see everyday.

TYPES OF STEEL TRUSSES

Steel is an indispensable part of construction and engineering. Builders use it in various forms, such as plates, trusses, and steel beams. They choose steel trusses because of their strength and ability to form long-lasting structures. Steel trusses are lightweight, have a reduced deflection, and have the ability to carry a heavy load.

Some different types of steel trusses are mentioned below:

1. HOWE TRUSS

Howe Truss is a blend of wood and steel. Steel provides extra durability and a longer life span to howe truss bridges. Engineers widely use this versatile type of steel truss in the construction of bridges. In short, people call the bridges made with Howe trusses “Howe truss bridges.”

2. PRATT TRUSS

This is one of the most common types of steel truss. The members placed vertically respond to compression while they built the diagonal ones for the forces of tension. Pratt Truss is an excellent steel truss for buildings with a span of around 20 to 100 m.

3. WARREN TRUSS

Warren truss have a lesser number of members than above mentioned Pratt truss. This steel truss consists of diagonal members that alternate force between compression and tension.

4. FLAT TRUSS

Engineers construct floors or flat roofs with the help of a flat truss. Here, the top and bottom chords are parallel to each other.

5. KING POST TRUSS

This is an elementary truss and is simple to fabricate. The truss has support members that are two-angled. These trusses are usually used for a brief span of nearly 8 meters. This truss is ideal for small houses.

6. QUEEN POST TRUSS

Quite similar to King Post truss, Queen Post truss is also easy to fabricate. Queen Post truss is also very versatile to use. Builders use this truss for brief spans of nearly 10 meters. Two horizontal members comprise a beam in the center for support. This truss is ideal for roofs, covered bridges, etc.

Some lesser-used forms of trusses are as follows:

1. Hip truss
2. Bowstring truss
3. Fan truss
4. Fink truss
5. Scissor roof truss

Read More – Advantages And Disadvantages of Truss Bridges

TYPES OF TRUSS BRIDGES: EXAMPLES

With this in mind, a truss bridge is a type of bridge whose load-bearing structure comprises a truss. The main type of truss bridges consists of basic truss designs that are easy to analyze by the engineers of the 19th and early 20th centuries. What’s more! A truss bridge is very economical and commercially helpful as it uses materials efficiently and in less quantity.

Summing up, some examples of famous truss bridges are as follows:

1. EARLE C. CLEMENTS BRIDGE, USA
2. TENMON BRIDGE, JAPAN
3. DASHENGGUAN BRIDGE, CHINA
4. HOWRAH BRIDGE, INDIA