In a plate girder, the distance between the centroid of the compression flange and the centroid of the tension flange is termed what?

Introduction / Context:
Bending resistance of a girder depends on the lever arm between compression and tension resultants. The relevant geometric quantity is the distance between the centroids of the compression and tension flanges, commonly called the effective depth for bending calculations.

Given Data / Assumptions:

• Flange centroids carry compressive and tensile stresses under bending.
• We distinguish between overall, clear, and effective depth.

Concept / Approach:
Overall depth measures outside-to-outside dimension, including flanges. Clear depth typically refers to the web depth between flanges. Effective depth is the centroid-to-centroid spacing of flanges, which directly contributes to section modulus and bending capacity.

Step-by-Step Solution:
Identify the centroids of compression and tension flanges. Measure the distance between these two centroids. This distance is termed the effective depth.

Verification / Alternative check:
Section modulus Z is related to the distance from the neutral axis to the extreme fiber; effective depth correlates with the lever arm of flange forces, aligning with bending theory for plate girders.

Why Other Options Are Wrong:

• Overall depth: includes thicknesses and covers; not centroidal spacing.
• Clear depth: refers to web depth between flanges.
• None: incorrect since a standard term exists.

Common Pitfalls:

• Using overall depth in place of centroidal spacing for precise bending lever-arm calculations.

Final Answer:
Effective depth.