In which of the following truss members the stress depends upon whether the load is moving on top chord or bottom chord?

Components of roof trusses are:

1. Upper chord members: The uppermost line of members which extend from one support to the other through the apex is called the upper chord.

2. Bottom chord members: The lowermost line of members which extend from one support to the other through the apex is called the lower chord.

3. Web members or diagonals: The top and the bottom chord members are connected by vertical or diagonal members called web members.

In trusses simply supported at the ends, the members in the top chord are subjected to compression and the members of the bottom chord are subjected to tension. Tension members are called ties while compression members are called struts.

A roof truss will slightly deflect under a vertical or moving load. The upper chord will be under compression while the lower chord is under tension. Diagonals can either be compression or tension members depending on their inclination. Therefore, diagonals are truss members the stress depends upon whether the load is moving on the top chord or bottom chord.