For an inaccessible roof in building design (i.e., not intended for regular occupancy), what live load should be considered for structural design calculations?

Introduction / Context:
Structural design must account for appropriate live loads as per occupancy and usage. Roofs that are not intended for regular foot traffic (inaccessible roofs) still require a nominal live load to cover occasional access for inspection and maintenance.

Given Data / Assumptions:

• Roof is designated inaccessible (no regular occupancy or assembly use).
• Loads are to be taken as uniformly distributed for design.
• Local code conventions equivalent to 0.75 kN/m2 are recognized as 75 kg/m2.

Concept / Approach:
Design standards typically prescribe a minimum live load for inaccessible roofs to ensure safety during maintenance. While accessible or landscaped roofs can require higher loads, the baseline for inaccessible roofs is significantly lower but non-zero.

Step-by-Step Solution:
Identify roof category: inaccessible.Apply prescribed nominal live load: 75 kg/m2.Ensure combinations with wind, seismic, and ponding checks as applicable.

Verification / Alternative check:
Conversion check: 75 kg/m2 ≈ 0.75 kN/m2, which aligns with common building code prescriptions for inaccessible roofs. This value provides a safety buffer for occasional maintenance loads without overdesigning the structure.

Why Other Options Are Wrong:

• Nil: unsafe, ignores maintenance access.
• 150 kg/cm2: incorrect unit and unrealistically large.
• 200 kg/m2: applicable to more heavily used roofs, not typical for inaccessible types.

Common Pitfalls:
Confusing accessible terraces with inaccessible roofs; using incorrect units (kg/cm2 rather than kg/m2) leading to gross errors in design forces.

Final Answer:
75 kg/m2.