Correct Answer - Option 1 : Rafters
Concepts:
The members which support covering material of a steel roof truss are called rafters.
Purlins are beams of light sections spanning between trusses carrying dead load of roof, live load and wind load. Purlins transmit these loads to the trusses. Generally, the purlins are so spaced that they are supported over the top chord joints of the truss.
Purlins may be angles, channels, I-sections, tube sections etc. They are placed in an inclined position over the main rafters (top chord) of the trusses.
To avoid bending in top chord, it is theoretically desirable to place purlins at panel points however; they are placed at very closed intervals for economic point of view.
A strut is a structural component of a roof truss and designed to resist longitudinal compression.
