Final answer:
The vertical steel post supporting the main girder is known as a column or a pillar, which is essential for transferring the load from the girder to the foundation.
Step-by-step explanation:
The vertical steel post that supports the main girder is known as a column or a pillar. In architecture and structural engineering, this component is critical for carrying the loads from the main girder to the foundation.
The main girder, being a principal beam that supports loads across large spans, relies on these posts for stability and support.
Columns can come in various forms and materials but in the context of a steel structure, a steel column would typically be used.
It ensures the integrity of the structure by distributing the loads and provides resistance against buckling under the weight of the building.