truss

A truss is a structural framework composed of straight members connected at their ends to form triangular units. The primary purpose of a truss is to carry loads, such as gravity and wind, with members that are subjected mainly to axial tension or compression rather than bending. The triangular arrangement provides stability and efficient use of material by distributing loads through triangulated geometry.

Planar trusses are two-dimensional frameworks used in roofs and bridges, while space trusses are three-dimensional structures used in large spans and modern architectural frames. Common planar configurations include Pratt, Howe, Warren, and K-trusses, as well as simple King-post and Queen-post roof trusses. Analysis typically uses the method of joints or the method of sections, assuming pin joints and members that carry axial forces.

Materials range from wood and steel to aluminum and composites. Truss members may be connected by rivets, bolts, welds, or pinned joints, depending on era and application. Fabrication emphasizes member straightness and accurate connections to maintain geometric stability.

Applications include roof framing for residential and industrial buildings, bridges, transmission towers, cranes, and space-frame architectural structures. Advantages include efficient material use for long spans and straightforward load transfer. Limitations include sensitivity to fabrication tolerances, the requirement for accurate joints, and reduced stiffness under certain dynamic or out-of-plane loads.

Historically, trusses have been used since ancient times in roof framing; the modern ability to analyze and optimize trusses developed in the 18th and 19th centuries. Design considerations focus on member sizing to resist axial forces, buckling in compression members, and ensuring reliable joint connections.