Terminology in floor systems: In building structures, a major primary beam supporting secondary members is commonly referred to as which of the following?

Introduction / Context:
Floor systems often use a hierarchy of members: joists or secondary beams supported by major primary beams, which in turn transfer loads to columns. Correct terminology helps avoid detailing and communication errors on drawings and schedules.

Given Data / Assumptions:

• “Major beam” means the primary supporting member in a framing bay.
• Secondary beams or joists frame into the major member.

Concept / Approach:
Conventionally, the principal beam carrying the secondary framing is termed a girder. “Floor beam” and “main beam” may be used broadly, but in strict usage a floor beam can itself be secondary, and “main beam” is generic without distinguishing hierarchy. The clearest, standard term is girder for the primary member.

Step-by-Step Solution:
Identify member hierarchy: primary vs. secondary.Apply standard nomenclature: primary = girder, secondary = beam/joist.Choose the term most specifically denoting the major primary member.

Verification / Alternative check:
Coding systems and typical steel manuals use “girder” for primary beams supporting other beams; general arrangement drawings reflect the same convention.

Why Other Options Are Wrong:

• “Floor beam” and “main beam” are less precise; not always reserved for primary members.
• “All the above” would blur important distinctions in detailing and specification.

Common Pitfalls:

• Interchanging terms in calculations and schedules leading to misfabrication.

Final Answer:
a girder