A truss is a structure made by connecting straight elements into a series of triangles. This simple-sounding design is incredibly strong and efficient, which is why you see it everywhere, from towering bridges and stadium roofs to the frames of houses and bicycles. The secret to its strength lies in the triangle, a shape that doesn't easily deform under pressure.

By arranging members into a network of triangles, a truss can support heavy loads over long spans using surprisingly little material. This makes it a go-to choice for engineers looking to build structures that are both strong and lightweight.

Every truss is built from a few key components. The straight pieces are called members, and the points where they connect are called joints or nodes.

Members have specific names depending on their location:

• Chords are the members that form the top and bottom outlines of the truss. You'll hear them called the top chord and bottom chord.
• Web members are the internal members that connect the chords. They can be vertical or diagonal.

When a load is applied to a truss, forces travel through its members. Each member experiences one of two types of internal force: tension or compression.

Tension is a pulling force. Think of a rope in a game of tug-of-war. The rope is in tension as both teams pull on it.

Compression is a pushing or squeezing force. Imagine squeezing a spring between your fingers. The spring is in compression.

In a well-designed truss, the members work together, with some in tension and others in compression, to efficiently transfer the load to the structure's supports.

To make analyzing these forces manageable, engineers start with a few simplifying assumptions. These create an idealized model of the truss.

1. Loads are applied only at the joints. We assume that any weight or external force on the truss acts directly on the nodes, not in the middle of a member. This prevents members from bending.

2. Members are connected by frictionless pins. Imagine each joint as a single pin that allows the members to rotate freely. This assumption means that forces are transferred directly along the length of each member, ensuring they are only in pure tension or compression.

While real-world joints aren't perfect pins and loads can sometimes be applied between joints, this idealized model is remarkably accurate for understanding the fundamental behavior of most truss structures. It provides the foundation for all further analysis.