At the early stages of the project, various forms of steel framing and precast construction were discarded in favour of a reinforced-concrete frame using flat-slab construction. This provided fl exibility in responding to irregular apertures, projecting features, the shape of the site and the interface with existing buildings. It gave a flat soffit to the floor slabs which could be expressed in combination with a regular grid of exposed circular reinforced-concrete columns. For the basement construction, we used a driven sheet pile solution with reinforced-concrete raft foundation and lining walls. The basement is protected from water ingress by a drained cavity system. The adjacent hospital building contained a series of functioning operating theatres in close proximity to the site. The demolition of the existing buildings had to be done within very tight time constraints defined by the use of these operating theatres. In addition, the new building could not take support from the existing building. This resulted in some complicated cantilevered foundations with mini-piling designed to clear the foundations of the existing building. The roof was constructed with a lightweight steel frame with metal deck above the sixth-floor plantroom.
Following the relocation there of the water tank, the sixth-floor concrete flat slab had to bear a much heavier load than anticipated. This was resolved by altering our analysis parameters for the existing reinforcement bars. Similar structural reconsiderations were prompted when the east facade panels' pre-agreed opening positions were altered significantly. Complicated structural problems did arise - particularly with the structures between the new and existing hospital - but these were minimised by having a fully coordinated design team and by having access to detailed structural information on the Institute of Ophthalmology Building. This proved invaluable while we developed the design of the steel link bridge between the two buildings.