The ultimate strength calculation may require consideration of the following:
- a) Loss of equilibrium of the structure or any part of it, considered as a rigid body; and
- b) Failure by excessive deformation, rupture or
Table 4 Partial Safety Factors for Loads, , for Limit State
(Clauses 3.5.1 and 5.3.3)
| Combination (1) | Limit State of Strength | Limit State of Serviceability | |||||||
|---|---|---|---|---|---|---|---|---|---|
| DL | LL'' | WL/EL | AL | DL | LL'' | WL/EL | |||
| Leading | Accompanying | Leading | Accompanying | ||||||
| (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) | |
| DL+LL+CL | 1.5 | 1.5 | 1.05 | — | — | 1.0 | 1.0 | 1.0 | — |
| DL+LL+CL+ | 1.2 | 1.2 | 1.05 | 0.6 | — | 1.0 | 0.8 | 0.8 | 0.8 |
| WL/EL | 1.2 | 1.2 | 0.53 | 1.2 | — | — | — | — | — |
| DL+WL/EL | 1.5 (0.9)² | — | — | 1.5 | — | 1.0 | — | — | 1.0 |
| DL+ER (0.9)² | 1.2 | 1.2 | — | — | — | — | — | — | — |
| DL+LL+AL | 1.0 | 0.35 | 0.35 | — | 1.0 | — | — | — | — |
- ¹⁾ When action of different live loads is simultaneously considered, the leading live load shall be considered to be the one causing the higher load effects in the member/section. ²⁾ When determining the stability of a structure, the dead load contributes to stability against overturning is critical as the dead load causes
- higher load effects in the member section.
- This value is to be considered when the dead load contributes to stability against overturning is critical or the dead load causes reduction in stress due to other loads.
Abbreviations:
Abbreviations. DL = Dead load, LL = Imposed load (Live loads), WL = Wind load, CL = Crane load (Vertical/Horizontal), AL = Accidental load, ER = Erection load, EL = Earthquake load. NOTE: The effects of actions (loads) in terms of stress or stress resultante may be obtained from an appropriate method of analysis
NOTE — The effects of actions (loads) in terms of stresses or stress resultants may be obtained from an appropriate method of analysis as in 4.
loss of stability of the structure or any part of it including support and foundation.
5.4.1 Design Strength
The Design Strength, , is obtained as given below from ultimate strength, and partial safety factors for materials, given in Table 5.
where partial safety factor for materials, accoun for:
- a) Possibility of unfavourable deviation of material strength from the characteristic value,
- b) Possibility of unfavourable variation of member sizes,
- c) Possibility of unfavourable reduction in member strength due to fabrication and tolerances, and
- d) Uncertainty in the calculation of strength of the members.