Which structural design concept ensures members only experience direct stresses?

The concept that ensures structural members only experience direct stresses is trusses. Trusses are designed to distribute loads through a series of interconnected elements that primarily carry axial forces, which means they are designed to handle either tension or compression without bending or shear forces affecting them significantly. This direct stress application allows trusses to be efficient in material use and effective in spanning large distances while maintaining structural integrity.

The configuration of trusses—comprising triangular units—ensures that loads are transferred directly along the member lines, thus maximizing their strength while minimizing weight. This is especially crucial in construction, where reducing the load on supporting structures can lead to safer and more economical designs. The design nature of trusses ultimately contributes to their widespread use in roofs, bridges, and other structures.

In contrast, while grillages, cantilever beams, and slender columns have their own unique benefits and applications, they may experience other types of stresses due to their particular configurations and load applications, making them less optimal for ensuring that only direct stresses are present.