Which of the following is NOT a type of truss system?

The reason concrete is not considered a type of truss system lies in the fundamental design and structural characteristics of trusses themselves. A truss is a framework consisting of triangular units that are used to support loads over spans. Trusses typically rely on materials that can efficiently handle tension and compression, such as wood, steel, or even lightweight alloys.

Concrete, on the other hand, is generally used as a solid mass material in construction. Its properties make it excellent for compression but less effective in tension, which does not align with the typical functions and advantages of truss systems.

Lightweight wooden, heavy timber, and steel trusses are all examples of frameworks designed for supporting structures and spanning large distances with reduced material use. These materials take advantage of the truss' geometry to efficiently distribute loads while minimizing weight, making them practical for construction purposes.