There absolutely is a ton hidden. Your ASTM A992 structural steel W-beam (wide I beam) or S-beam (standard I-beam) is abstracting a ton of details with regards to:
- the construction process.
- material composition.
- thicknesses of the flange.
- width of the flange.
- depth/height.
- max length.
- shear strength.
- tensile strength.
- elongation (stretch/sag when approaching the point of failure).
- corrosion resistance.
- tolerances.
- cost per foot.
And the list only goes on.
A structural engineer can say "I have a specific structure in mind and need a beam that can withstand XYZ conditions" and pick out the matching beam from a table without considering any of the details as to how one would actually achieve those properties and withstand those conditions.
Alternatively an engineer can know their budget, what grade of steel, and what size of beam they want to use ahead of time and simply design a structure using those abstracted pieces in coordination with the architect.
Beams and other construction elements are the structural engineer's equivalent of a Hardware Abstraction Layer (coming from the perspective of an engineer who works close to the metal when I can). It lets the engineer abstract most of the minutiae regarding working with the hardware itself by giving the engineer a largely uniform interface for choosing how their product interacts with the world. Generally the abstraction holds but sometimes it's leaky and details show through. Likewise sometimes the abstraction is insufficient and the engineer has to do some custom work that breaks away from the established path to meet the constraints.
