Grillage footing for two unequal column loads: For a steel grillage footing supporting two unequal column reactions, which of the following statements are followed to achieve uniform pressure and practical detailing?

Introduction / Context:Grillage footings distribute heavy column loads to soil using tiers of steel beams and base plates. When adjacent columns have unequal reactions, the footing layout must ensure uniform soil pressure and manageable bending in the grillage beams.

Given Data / Assumptions:

• Two column loads of different magnitudes act on a common grillage base.
• Objective: maintain uniform soil pressure and efficient beam design.

Concept / Approach:The resultant of column loads should pass through the centroid of the base area to avoid net overturning or differential soil pressure. A trapezoidal footprint is a practical response to unequal loads, aligning area with reaction demand. Lower-tier beam projections (cantilevers beyond the column faces) are adjusted to balance bending under each column and between them.

Step-by-Step Solution:

Verification / Alternative check:Check soil pressure uniformity (q = R / A) and verify no uplift; ensure beam bending and shear capacities are adequate with serviceability checks.

Why Other Options Are Wrong:Individually, each statement addresses only part of the solution; the combined approach is required, hence “All the above”.

Common Pitfalls:Ignoring the location of the resultant; using a rectangular base without checking pressure eccentricity; neglecting differential bending under unequal loads.

Final Answer:All the above