The salient dimensions relate to the maximum escape run from the furthest corner of the working area to the safety of the enclosed stairs. Protected lobbies or passages can extend these lengths. The basic arrangement is given in Figures 3.4a-c with guidance on limiting factors in the UK and abroad.
The core locations depend upon the floor configuration adopted. For high rise, slab block versus tower has to be considered. For medium rise, further comparisons need to be made with atrium and courtyard forms as well as geometries involving irregular-shaped buildings. Figures 3.5 and 3.6 provide a diagrammatic guide with references to typical designs. The obvious criteria from the economic viewpoint are core sizes that can be expressed as the smallest proportion of the rental and usable floors. For users there is another critical factor, namely the largest areas that can be accommodated at any single floor despite breaks incurred through lift and stair locations. The present interest with atria-based forms has produced deep floor plans of extended 'racetrack' layout with cores distributed along the edges, as at No. 1 Finsbury Avenue (Figures 3.7 a—c). Triple-bay depths have the advantage of layering plans so that the central zone can accommodate cores and servant spaces with the daylit outer zone used for prime activity. Racetrack plans of these patterns are used for highly serviced office buildings. They also apply to educational facilities, hospitals and laboratories where servicing is centrally located.
More extreme separation in the elements can be seen at the Lloyd's Building, London, and with the Hong Kong and Shanghai Bank where external towers provide lift and stair cores. These 'servant' features are placed outside the uninterrupted volume of atria and related offices. The escalators for both buildings are illustrated in detail in Figures 2.19 and 11.5).
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