Plate girder terminology: When no horizontal stiffeners are provided, the distance between the vertical legs of the top and bottom flange angles (i.e., the clear distance between the inner faces of the flange angles) of a plate girder is called what?

Introduction / Context:
In steel plate girders, three different depth terms are routinely used in design and detailing: overall depth, clear depth, and effective depth. Examiners often test whether learners can correctly identify each from a verbal description or a simple sketch. This question focuses on the name for the distance between the inner faces of the flange angles when horizontal stiffeners are not present.

Given Data / Assumptions:

• A riveted/bolted plate girder with angle sections forming the top and bottom flanges.
• No horizontal stiffeners are used along the web.
• We are referring specifically to the distance between the vertical legs of the flange angles.

Concept / Approach:
Overall depth is the total depth of the girder, typically measured between the outermost surfaces of the top and bottom flanges or cover plates. Effective depth is the distance between the centroids of the compression and tension resultants (often approximated to the distance between the centroids of flange areas for preliminary design). The distance strictly between the inner faces of the flange angles is termed the clear depth. This dimension is frequently used for checking web slenderness and spacing of vertical stiffeners.

Step-by-Step Solution:
Identify the two reference faces: inner faces of the vertical legs of top and bottom flange angles.Recognize that this excludes any cover plates, fillets, or external projections.The standard term for this measurement is clear depth.

Verification / Alternative check:
Design handbooks define clear depth as the net web panel height available between flange connections. This is the controlling panel dimension for stiffener spacing checks and web buckling calculations in plate girders without horizontal stiffeners.

Why Other Options Are Wrong:

• Overall depth: includes flange thicknesses and any cover plates; it is larger than the inner-to-inner distance.
• Effective depth: relates to internal force couple arm, not a simple inner-face-to-inner-face measurement.
• None of these: incorrect because a standard term (clear depth) exists.

Common Pitfalls:

• Confusing clear depth with web plate height; fillets and connection geometry can create slight differences.
• Using overall depth in web slenderness checks where clear depth is appropriate.

Final Answer:
clear depth