Working stress design (IS 800:1984) — factor of safety for axial compression What factor of safety did IS 800:1984 adopt while arriving at the permissible stress in axial compression?

Introduction / Context:
In the working stress method (WSM), permissible stresses are obtained by dividing a reference (usually yield) strength by a factor of safety (FoS). IS 800:1984, which used WSM, specified distinct permissible stresses for tension, compression, bending, etc., implying underlying FoS values.

Given Data / Assumptions:

• Indian Standard IS 800:1984 (Working Stress Method era).
• Member under axial compression.
• FoS is applied to yield or critical stress to obtain a permissible value.

Concept / Approach:
Typical WSM practice in steel assigns FoS around 1.67 against yielding for ductile limit states, leading to permissible stresses ≈ 0.6 fy in tension/compression before buckling reductions. For compression members, additional column curves or slenderness reductions apply, but the base FoS figure of 1.67 underpins the permissible stress derivation.

Step-by-Step Solution:
1) Recall that FoS in WSM for steel ≈ fy / σ_perm.2) With σ_perm around 0.6 fy, FoS ≈ 1 / 0.6 ≈ 1.67.3) For compression, further reductions are applied via buckling curves, but the FoS basis remains ≈ 1.67.4) Select 1.67.

Verification / Alternative check:
Permissible stresses tabulated in IS 800:1984 back-calculate to FoS near 1.67 against yield for ductile limit states.

Why Other Options Are Wrong:
2.00 is overly conservative for WSM steel; 1.50 aligns more with some ultimate limit states partial safety factors, not WSM permissible stresses; 1.00 is unsafe.

Common Pitfalls:
Confusing WSM factors with limit state partial factors; overlooking additional buckling reductions beyond the basic FoS.

Final Answer:
1.67