Steel Design (IS 800:1984) – Maximum Slenderness Ratio As per IS 800:1984, the maximum allowable slenderness ratio (KL/r) for compression members carrying forces due to dead load plus superimposed load is:

Introduction / Context:Slenderness ratio limits control buckling susceptibility of compression members. IS 800 specifies maximum KL/r values depending on the nature of loading and whether the member is part of a bracing system, a member under wind/seismic forces only, or a member carrying sustained loads.

Given Data / Assumptions:

• Code: IS 800:1984 (working stress era provisions).
• Member: compression member carrying dead load plus superimposed load (sustained).
• Objective: recall the prescribed maximum KL/r.

Concept / Approach:

Under sustained gravity loads, lower slenderness is mandated to limit buckling and service deflections. The code stipulates KL/r ≤ 180 for such compression members, with higher limits reserved for members under transient wind/earthquake loads or tension-only bracing components when un-stressed under normal loading.

Step-by-Step Solution:

Verification / Alternative check:

Cross-reference with summarized tables in steel design handbooks reproducing IS 800:1984 limits: 180 (sustained compression), 250–300 for wind/seismic-only conditions in certain cases.

Why Other Options Are Wrong:

• 250, 300, 400: These are larger limits applicable to different categories, not to members carrying dead plus imposed loads.

Common Pitfalls:

Applying relaxed limits meant for wind/seismic-only members to gravity-carrying columns or struts.

Final Answer:

180