Why can an uncoupled uniform Winkler mesh misstate bending demand in a raft compared with a calibrated contact pressure footprint?

Choices

• (A) A single modulus blanket ignores shear gradients that redistribute uplift pockets under one slab bay
• (B) Soils never develop non-uniform bearing bulbs near column drops
• (C) Raft slabs behave as membranes immune to twisting
• (D) Uniform springs are invariably conservative for negative moments