In a plate girder, tongue plates are typically provided at which location to facilitate connection between web and flange components?

Introduction / Context:
Plate girders are fabricated from flange plates/angles and a web plate. At the junctions of the web with flanges, detailing components such as tongue plates help achieve proper fit-up, load transfer, and connection of cover plates or angles—especially near splices and ends.

Given Data / Assumptions:

• We are concerned with where tongue plates are placed in relation to the web and flanges.

Concept / Approach:
Tongue plates are small connection plates projecting from the web to assist in attaching flange elements at both the top and bottom. Providing them at both web ends ensures symmetry, simplifies erection, and allows consistent load transfer from the flange components into the web, particularly during splicing or cover-plate transitions.

Step-by-Step Solution:
Identify the interface needing the accessory plate: web-to-flange. Recognize the mirror requirement at top and bottom to carry moment flange forces. Select placement: at both the upper and lower ends of the web.

Verification / Alternative check:
Fabrication drawings for built-up girders depict tongue/cover arrangements at both flanges; field practice relies on symmetric detailing to avoid eccentricities and ease assembly.

Why Other Options Are Wrong:

• Single-end locations provide incomplete detailing; both ends are typically required.

Common Pitfalls:

• Confusing tongue plates with stiffeners; stiffeners are different components used for web stability and bearing.

Final Answer:
At both the upper and lower ends of the web.