What is the reference point used to determine all other elevations of structural steel members?

The benchmark is the correct reference point used to determine all other elevations of structural steel members. It serves as a fixed point of known elevation that helps ensure consistency and accuracy in construction projects. When setting out a structure, all measurements and elevations for each component are taken relative to the benchmark. This ensures that every part of the steel framework is positioned correctly in relation to one another, which is crucial for safety and structural integrity. Benchmark points are often established during the site preparation phase and can be verified using surveying techniques.

In contrast, while other terms like the base point, reference line, and datum point might be relevant in specific contexts, they do not universally serve the same foundational purpose as a benchmark does in construction and structural engineering.