ABSTRACT
Some more recent developments are shown in Figure 11.2. Figure 11.2a depicts a type of bridge deck developed and used by British Railways (Eastern Region)^. This design is based on a system proposed by Hajnal-Konyi^, in which the prestressed beams are designed to carry their own dead weight, together with that of the additional concrete, without props, and the composite slab is designed to support all additional dead loads and live loads. A further development of this principle is the ‘wafer’ slab bridge deck^ , also designed and used by British Railways (Eastern Region), shown in Figure 11.2b, in which further prestress is applied to the composite section after the added concrete has hardened. A composite beam devised by Samuely^5\ in which castellated prestressed planks are used at the tensile face is shown in Figure 11.2c
and a type of composite floor in which prestressed planks are used to support the weight of hollow tiles and the additional concrete during construction is shown in Figure 1 1.2d^. During the last ten years a combination of precast-T and double-T units with in-situ added concrete has been extensively used (Figure 11.2e).
