FOS is required to bring the structure from the state of collapse to the useable state. It additional covers the following affects
- Uncertainties in applied forces or load, The structure should be able to with stand the loading approve up to structure external without failure of structure.
- The deflection should be small as structure load condition.
- To cover uncertainties in material strength when the material used in under strength.
- Cover in part poor workman ship.
- To cover unexpected behavior in case the theory is not fully develop.
- To cover natural disasters.
- The stress produced to interdiction and erection due ro storage of material movement of machinery and labor may be very high, Factor of safety make take care of these loads during construction.
- Presence of stress concentration beyond the level theoretically expected.