Flat slab — support system identification A flat slab is a reinforced concrete slab with or without drops that is supported how?

Introduction / Context:
Flat slab construction eliminates the need for traditional beams, transferring slab loads directly to columns. It may have drop panels and sometimes column capitals (heads) to reduce punching shear and improve moment transfer.

Given Data / Assumptions:

• Terminology follows conventional RC building practice.
• Slab may have drops; column heads may or may not be present.
• We are distinguishing flat slab from beam-and-slab systems.

Concept / Approach:
A defining characteristic of a flat slab is that it spans directly onto columns, not onto beams. The presence of column heads is optional; many systems use drops alone, while others use both. What is not a flat slab is a two-way slab carried by beams (that is a beam-and-slab or flat plate with beams, not a flat slab system).

Step-by-Step Solution:
Step 1: Identify support: direct support by columns is essential.Step 2: Recognize optional features: drops and column heads may be provided to control punching and negative moments.Step 3: Exclude support by beams; if beams carry the slab, it is not a flat slab system.

Verification / Alternative check:
Textbooks define flat slabs as slabs supported directly by columns with or without column capitals and drop panels; a slab resting on beams is classified differently.

Why Other Options Are Wrong:
Only 'without heads' or only 'with heads': Each is incomplete; both arrangements are valid.
'On beams': Contradicts the definition of flat slab.
'On walls only': Not the intended structural system for flat slabs.

Common Pitfalls:

• Confusing flat plate (no drops, no heads) with general flat slab; both are column-supported without beams.
• Assuming presence of beams at column lines still qualifies as flat slab; it does not.

Final Answer:
On columns (with or without column heads), not on beams