T-beam effective flange — the portion of slab that may be considered to act effectively with the rib (web) of a T-beam depends on which geometric parameters?

Introduction / Context:
The effective flange width in a T-beam captures how much of the slab actually participates in compression with the beam web. Because stress distribution in the slab is non-uniform (shear lag), design codes cap the effective flange width using several geometric limits to prevent unconservative assumptions.

Given Data / Assumptions:

• Monolithic slab–beam construction forming T-sections under sagging moment.
• Need to identify the variables governing effective flange width.
• Typical code limits involve span, spacing, and slab thickness along with web breadth.

Concept / Approach:

Effective flange width is influenced by: (1) span (longer spans allow wider stress spread), (2) spacing between adjacent beams (flange cannot exceed half-spacing each side), (3) slab thickness (thicker slabs distribute compression more effectively), and (4) web breadth (local participation right above the web). Thus, all the stated geometric factors matter.

Step-by-Step Solution:

Verification / Alternative check (if short method exists):

Compute each limit for a given geometry and select the least value to remain conservative.

Why Other Options Are Wrong:

Each single-parameter option is incomplete; codes use multiple simultaneous limits.

Common Pitfalls (misconceptions, mistakes):

Equating effective flange width to the full tributary slab width; forgetting to adopt the minimum of the applicable limits.

Final Answer:

all the above