Self-weight is the load on a structure imposed by its own weight. Self-weight is directly influenced by the material density of the structure. By default, self-weight is turned off and needs to be enabled if it is to be modelled.
The self-weight will depend on 1) the material and 2) the section of each member. It is recommended to double-check the materials and sections used within your project so that the self-weight of your structure is as accurate as possible.
The self-weight window allows you to specify multipliers to acceleration due to gravity (g) in the X, Y, and Z axes. If it is switched on, the default self-weight acts in the Y-axis with a magnitude and sign of -1.