The truss, as we know, is composed of members and connections at its ends. Let's now take a closer look at these parts and discuss specific terminologies.
There may be more specific terms that you may encounter, especially in construction engineering, such as 'king post' or 'strut' - we will NOT delve into those. We're interested in terminologies related to structural analysis.
Members
The members of the truss are its long slender components. There are two essential types:
Chords
The chords are the 'perimeter members' of the truss. Essentially, these members define the shape of the truss.
In our example, we have members \(AB\), \(BD\), and \(DE\) as top chords while members \(AC\) and \(CE\) are bottom chords. Whether the member is a top or bottom chord will depend on the purpose of the truss. For example,
- For a roof truss, members that carry the roof and purlins directly are the top chords. Any chord that does not withstand these loads is the bottom chord.
- For a bridge truss, members supporting the road are the bottom chords, while the other chords are the top chords.
Webs
Anything that is not a chord is a web member. Some references refer to it as the diagonals because the diagonal truss members are usually the webs. In our example, the web members are \(BC\) and \(CD\)
Webs usually maintain the shape defined by the chord members. Generally, these are responsible for maintaining the rigidity of the truss.
Connections
The connections at the end of the truss members are commonly called joints. Going back to our example, we have 5 joints: \(A\), \(B\), \(C\), \(D\), and \(E\).
The joints are locations where the external load is applied. Later on, we'll discuss basic analysis assumptions related to these connections.
Summary
The members of the truss are its long slender components.
The chords are the 'perimeter members' of the truss. It defines the shape of the structure.
Whether the member is a top or bottom chord will depend on the purpose of the truss.
Anything that is not a chord is a web member.
The connections at the end of the truss members are commonly called joints.
