3.1. Introduction

A truss is an assemblage of straight members connected at their ends by flexible connections to form a rigid configuration.

A truss is essentially a structure made up of straight beams or bars that are arranged in a specific way. These members are connected together at their ends. The connections are flexible but designed to keep the entire structure stable and firm. Trusses are commonly used in architecture and engineering due to their lightweight nature combined with high strength, which allows them to carry significant loads without excessive material use.

Imagine a large spider web where each thread is like a member of the truss. The connections where threads meet help maintain the overall strength and integrity of the web, allowing it to catch prey without collapsing under its own weight.

Because of their light weight and high strength, trusses are widely used, and their applications range from supporting bridges and roofs of buildings to being support structures in space stations.

Trusses are employed in various fields due to their efficient design. They can be found in structures like bridges, where they support loads over large distances, or in buildings, where they serve as roof frameworks. They are so sturdy that even in space stations, trusses help support the modules that house astronauts and equipment, showcasing their versatility beyond traditional construction.

Think of a bridge that uses a truss system: the triangle shape formed by the truss allows it to evenly distribute the weight of vehicles crossing over it, just like how a well-distributed load on a shelf keeps it from collapsing.

Modern trusses are constructed by connecting members, which usually consist of structural steel or aluminum shapes or wood struts, to gusset plates by bolted or welded connections.

Today's trusses are typically made using materials like structural steel or aluminum for their durability, or sometimes wood for lighter applications. The members (the straight bars) are attached to plates known as gusset plates, which help distribute forces among the members. These connections can be made using bolts or welds, providing strength and stability to the entire structure.

Consider a model airplane built with plastic struts connected at intersections using glue. These intersections behave like gusset plates, providing structure to the plane, just as a gusset plate provides support to the members in a truss.

If all the members of a truss and the applied loads lie in a single plane, the truss is called a plane truss. Plane trusses are commonly used for supporting decks of bridges and roofs of buildings.

A plane truss is defined as a truss where all its components are in one flat plane, which is essential for ensuring that the loads acting on it can be efficiently managed. This type of truss is particularly prevalent in practical applications, such as the flat roofs of buildings or the decks of bridges, where the design needs to effectively handle the downward forces from the structures on top.

Picture a flat tabletop supported by a network of struts underneath. The supports are like members of a plane truss, spreading the weight of objects placed on the table evenly across the surface, ensuring stability and preventing collapse.

Figure 3-1: Common roof trusses.

Although the figure is not included in the text provided, it typically represents various styles of trusses that are commonly seen in roof supports. These can illustrate the different shapes and arrangements that trusses can take, and provide practical examples of their application in real-world scenarios.

Looking at a house from the outside, the triangular shapes supporting the roof are made of trusses. Each triangle is designed to carry the weight of the roof while allowing for open spaces inside the house, similar to how a well-structured tent maintains its shape and stability.

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