Effective flange width of a T-beam in reinforced concrete design Given: b = actual (available) width of the slab/flange, Dt = thickness of flange, bw = breadth (web width) of the rib/web, l0 = distance between points of zero moment (effective span segment). Task: State the effective flange width expression using these symbols, as per standard code limits without introducing new symbols.

Introduction:
In reinforced concrete floor systems with monolithic slabs and ribs, T-beams are analyzed by replacing the slab over the web with an 'effective' flange width that realistically participates in flexure. This question checks your understanding of how codes cap that width using geometry and span parameters so bending stresses are evaluated correctly.

Given Data / Assumptions:

• b = actual slab width available as flange.
• Dt = thickness of the slab (flange thickness).
• bw = web (rib) width.
• l0 = distance between points of contraflexure (often approximated by the effective span for simple spans).

Concept / Approach:

The flange cannot be taken arbitrarily wide. Codes cap the effective flange width by several limits. When spacing to adjacent webs is not explicitly provided, the controlling limit is usually the lesser of the actual available slab width b and a span- and thickness-dependent expression: bw + (l0 / 6) + 6 * Dt. Taking the lesser prevents overestimation of compression block and moment capacity.

Step-by-Step Solution:

Verification / Alternative check:

If center-to-center spacing of beams were known, it would provide another upper bound. In its absence, using the lesser of b and bw + (l0/6) + 6Dt remains conservative and code-consistent.

Why Other Options Are Wrong:

Option B ignores mechanics and code caps. Option C exaggerates width with l0/3 and 12Dt. Option D underestimates the span/thickness influence. Option E incorrectly takes the greater, which is non-conservative.

Common Pitfalls:

Confusing l0/6 with l0/12 (edge beams) and forgetting the physical cap b are common errors.

Final Answer:

Effective flange width = lesser of { b , bw + (l0 / 6) + 6 * Dt }