Last edited 25 Nov 2020

Structure definition

Within the context of the built environment , the term ‘structure’ refers to anything that is constructed or built from different interrelated parts with a fixed location on the ground.

This includes buildings, but the term structure can also be used to refer to any body of connected parts that is designed to bear loads, even if it is not intended to be occupied by people. Engineers sometimes refer to these as 'non-building' structures. Common examples include:

Structural engineers design, assess and inspect structures to ensure that they are efficient and stable. Structural engineers work on a very wide range of structures, including; buildings, bridges, oil rigs, and so on.

Civil engineers design, construct, maintain and improve the physical environment, including bridges, tunnels, roads, railways, canals, dams, coastal defences, and so on. The term ‘civil’ engineer is a more broad one than ‘structural’ engineer that can include infrastructure such as pipelines, transportation, environmental engineering, maritime engineering, and so on. It was originally coined to distinguish it from military engineering.

Structural engineering was initially considered a sub-discipline of civil engineering, however it has developed into an important and complex specialism and is now be considered an specific engineering discipline in its own right.

According to William R Spillers 'Introduction to Structures', structural analysis ‘…is for the most part concerned with finding the structural response (the lateral deflection of a building under wind load, the reaction of a bridge to a moving train,…) given external loads. In all but the most trivial cases, real structures, that is structures without the simplifications commonly associated with analysis, turn out to be impossibly complex. And what is finally analysed – the structural model – may appear at first glance to be quite different than the real structure’.

In their most simple form, structural elements can be classified as:

One-dimensional: Ropes, struts, beams, arches.
Two-dimensional: Membranes, plates, slab, shells, vaults.
Three-dimensional: Solid masses.

Approved document B, Fire Safety, Volume 2, Buildings other than dwellinghouses, paragraph B3.iii defines ‘elements of structure’ as:

‘….the main structural loadbearing elements, such as structural frames, floors and loadbearing walls. Compartment walls are treated as elements of structure although they are not necessarily loadbearing. Roofs, unless they serve the function of a floor, are not treated as elements of structure. External walls, such as curtain walls or other forms of cladding which transmit only self weight and wind loads and do not transmit floor load, are not regarded as loadbearing…’

Very broadly, the 'substructure' refers to work below the underside of the screed or, where no screed exists, to the underside of the lowest floor finishes, and the 'superstructure includes works above that level. See Substructure and Superstructure for more detailed definitions.

NB The CDM Regulations suggest that structure means:

(a) any building, timber, masonry, metal or reinforced concrete structure, railway line or siding, tramway line, dock, harbour, inland navigation, tunnel, shaft, bridge, viaduct, waterworks, reservoir, pipe or pipeline, cable, aqueduct, sewer, sewage works, gasholder, road, airfield, sea defence works, river works, drainage works, earthworks, lagoon, dam, wall, caisson, mast, tower, pylon, underground tank, earth retaining structure or structure designed to preserve or alter any natural feature and fixed plant;