Difficulty: Easy
Correct Answer: Uniform over the base
Explanation:
Introduction / Context:
Contact-pressure assumptions depend on the relative rigidity of the footing and the soil. For a perfectly rigid footing on homogeneous soil under concentric vertical load, the conventional assumption is a uniform pressure distribution.
Given Data / Assumptions:
Concept / Approach:
Rigid base implies plane sections remain plane; with symmetry and no moments, the soil reaction is uniform to balance the applied load.
Step-by-Step Solution:
Verification / Alternative check:
Flexible bases show non-uniform distributions (often more at center); presence of moments shifts maxima to edges. The stated ideal leads to uniform pressure.
Why Other Options Are Wrong:
Edges higher or center zero require eccentricity or flexibility; arbitrary shapes contradict concentric, rigid conditions.
Common Pitfalls:
Confusing rigid with flexible base assumptions; ignoring effect of eccentric loading and rocking.
Final Answer:
Uniform over the base
Discussion & Comments