The combinations of actions to be taken into account in the relevant design situations should be appropriate for the serviceability requirements and performance criteria being verified.
a) Characteristic combination:
The characteristic combination is normally used for irreversible limit states.
b) Frequent combination:
The frequent combination is normally used for reversible limit states.
c) Quasi-permanent combination:
The quasi-permanent combination is normally used for long-term effects and the appearance of the structure.
As per IRC 6:
Clause 7.1, Rare combination for stress limit checking.
As per IRC 6:
Clause 7.3, Quasi-permanent Combinations for estimation of the permanent stress checking.
As per BS EN 1992-1-1:2004
Clause 7.2, the stress in the concrete under the quasi-permanent loads.
AS PER IRC 6
The rare combination of loads shall be used for checking the stress limit.
A frequent combination of loads shall be used for checking the deflection, vibration, and crack width.
The quasi-permanent combination of loads shall be used for checking the settlement, shrinkage creep effects, and permanent stress in concrete.