As per IS:800 guidance for members carrying loads resulting only from wind (or seismic), what is the maximum permissible slenderness ratio L_eff/r?

Introduction / Context:
Slenderness ratio (λ = L_eff / r) limits guard against elastic buckling and serviceability issues. For transient actions like wind or seismic, codes allow higher λ than for permanent gravity loads.

Given Data / Assumptions:

• Member resists only wind/seismic effects.
• λ checked about the least radius of gyration.

Concept / Approach:
IS practice permits λ ≤ 250 for wind-only members, balancing stability and economy because such loadings are occasional and short-duration.

Step-by-Step Solution:
Compute λ = L_eff / r_min.Ensure λ ≤ 250 for compliance.

Verification / Alternative check:
Design aids and MCQ standards list 250 as the upper bound for wind-only members.

Why Other Options Are Wrong:

• 180, 200: typical for permanent loads and compression members in buildings.
• 300, 350: exceed codal allowances.

Common Pitfalls:
Using r about the strong axis instead of r_min; ignoring end-condition factor in L_eff.

Final Answer:
250