The partial safety factor for loads to be adopted for Dead load (DL) and Live load (LL) for the combination of load taken as (DL + LL), under limit state of collapse, as per IS 456 : 2000, are _______ and _______respectively.
Concept: Factor of safety Yield stress is defined as the stress at which first fibre failure occurs .Working stress is defined as the stress which is safe to work on or it is the yield stress with factor of safety that the structure will not going to yield at this stress for a particular surrounding condition. Values of factor of safety (partial) for load combination:
Load combination
Ultimate limit state
Serviceability limit state
1) Dead load & live load
1.5(DL + LL)
DL + LL
2) Dead seismic/wind load a) Dead load contributes to stability b) Dead load assists overturning
0.9 DL + 1.5 (EQ/WL)
1.5 (DL + EQ/WL)
DL + EQ/WL
DL + EQ/WL
3) Dead, live load and Seismic/wind load
1.2 (DL + LL + EQ/WL)
DI + 0.LL + 0.8EQ/WL
Where, DL = Dead load, LL = Live load WL = Wind load EQ = Earthquake load Important Points: In WSM, the combined factor of safety is considered for incorporating effects of material quality and type of load. In LSM, separate factors of safety called as partial safety factors are considered for material quality and type of load.