strut
To brace or support (something) by a strut or struts; to hold (something) in place or strengthen by a diagonal, transverse, or upright support.
strut: to brace with diagonal members under load
To strut is to reinforce or support a structural member, opening, or assembly by installing diagonal or transverse bracing members, typically called struts. These compression members are designed to resist buckling and lateral movement in frameworks, formwork, and temporary structures. In construction, struting turns a flimsy or unsupported element into a rigid, load-bearing system.
The term applies across multiple contexts. In concrete formwork, you strut shoring towers and wall forms with diagonal timber or adjustable metal props to prevent collapse under the weight of wet concrete. In steel erection, diagonal braces and gusset plates strut beam webs and column flanges during assembly before final bolting or welding. In temporary works, struts support scaffold platforms, façade retention systems, and trench shoring at angles typically between 30 and 60 degrees to the vertical, where they carry both axial compression and some bending moment.
Struts and temporary stability
The strut member itself is usually straight and relatively slender, sized so that its slenderness ratio stays within safe limits to avoid Euler buckling. Common materials are timber (often softwood props or battens), adjustable steel or aluminium props, and timber or steel diagonals in assembled frames. The effectiveness of struting depends on fixing the ends properly: pinned connections are most common, though fixed or partial fixity can reduce required section size.
Where struting fails, structures sag, shift, or collapse catastrophically. Common failures occur when struts are too slender, improperly seated at bearing points (reducing end fixity), removed prematurely before concrete has gained strength, or overloaded by side loads or settlement. Site workers often underestimate the forces involved, particularly in lateral thrust from uneven concrete placement or wind loading.
The word strut itself derives from Old English meaning to stiffen or stand stiffly, which captures the engineering intent. In this figurative usage within construction, to strut something is to make it stand firm and unyielding against the forces that would move or deform it. This verbal form is distinct from the noun strut (the physical member), though both names share the same root and meaning.