Precast concrete beams
Beams are the main horizontal load-carrying members in skeletal structures. They are, by definition, relatively small prismatic sections of large flexural (typically, 300–800 kNm) and shear (100–500 kN) capacity. In the European product standards, they form part of ‘linear structural elements’ according to BS EN 13225 (2013) but note that this standard is for the beam itself and does not extend to the design of beams within the framework. In a precast concrete structure, they must at some point in time support the self-weight of the floor slabs alone and should therefore be capable of resisting all of the possible load combinations that precast construction brings – for example torsion will be present if, in the temporary construction stage, the floor units are all positioned on one side of the beam. This must be allowed for both in the design of the beam and at the end connections to the column.