What is the term for structures made of straight members arranged in triangles, primarily utilizing tension and compression?

The term for structures made of straight members arranged in triangles, primarily utilizing tension and compression, is trusses. Trusses are an efficient structural system as they distribute loads evenly through their triangular configuration. This design allows trusses to effectively resist various forces while minimizing the amount of material needed. The triangular shape is key because it prevents deformation and ensures stability under load, making trusses a preferred choice in applications such as bridges and roofs.

In contrast, while frames can also support loads, they typically consist of members connected at joints that can experience bending moments, which is different from the pure tension and compression found in trusses. Grids are more about a framework composed of intersecting members, often in a 2D or 3D pattern, and do not focus solely on the triangular arrangement. Struts are individual members that are part of a larger structure but do not imply the systematic arrangement found in a truss. Thus, the correct term to describe this structural concept is trusses.