Flat slab design terminology: The effective width of a column strip in a flat slab panel is taken as what fraction of the panel width for distribution of bending moments?

Introduction / Context:

Flat slab systems distribute bending between column strips (over supports) and middle strips (spanning between supports). Defining the effective column strip width is fundamental for moment allocation and reinforcement detailing.

Given Data / Assumptions:

• Two-way flat slab panel supported by columns.
• Conventional code-based proportioning of column and middle strips.

Concept / Approach:

Standard practice takes the column strip on each side of a column centerline as a fixed fraction of the panel width (commonly one-fourth of the panel width in the direction considered). The remaining portion is assigned to the middle strip for moment distribution.

Step-by-Step Solution:

Verification / Alternative check:

Flat slab design procedures (direct design method / equivalent frame) typically reference a 1/4–1/3 range; exam conventions often use 1/4 of panel width for the column strip.

Why Other Options Are Wrong:

• Half width: Over-broad; would starve middle strips of moment.
• Radius/diameter of the column: Column size does not directly define strip width.
• None: A recognized fraction exists in standard design methods.

Common Pitfalls:

• Confusing effective strip width with punching shear critical perimeters around columns.

Final Answer:

one-fourth the width of the panel