Flat slab terminology in building design: The locally thickened portion of a flat slab provided over a supporting column to reduce negative moments and punching shear is called what?

Introduction / Context:

Flat slab systems distribute loads directly to columns without deep beams. To control negative moments around column supports and to enhance punching shear capacity, designers commonly use local thickening or flaring near columns. Knowing the correct terminology is essential for detailing and communication.

Given Data / Assumptions:

• Flat slab with column supports.
• Local thickness increase of the slab over the column panel.
• No drop beams; two-way action prevails.

Concept / Approach:

The slab thickening over the column is called a drop panel. It reduces peak negative bending moments and increases the slab's punching shear capacity by increasing effective depth and critical perimeter. Related terms include capital or column head, which typically describe a flared enlargement of the column itself rather than a thickening of the slab plate.

Step-by-Step Solution:

Verification / Alternative check:

Design standards for flat slabs (direct design or equivalent frame methods) explicitly reference drop panels and column capitals, distinguishing their geometry and structural roles.

Why Other Options Are Wrong:

• Capital / column head: These are column enlargements, not slab thickenings.
• None of these: Incorrect because the established term is ‘‘drop panel’’.
• Haunch: More typical for beam-slab interfaces or precast connections.

Common Pitfalls:

• Confusing column capitals with drop panels; both may be used together in ‘‘mushroom’’ slabs but are distinct features.

Final Answer:

drop panel