Design selection and core planning

Selection of a system and operation depends upon design studies that take into account building use and occupancy. A single lift will generally only be suitable for a modest commercial building of five storeys and then provide poor service, there being no back-up if the lift is out of order.

Lifts are commonly grouped in pairs, fours etc., and are better distributed either side of a lobby which does not double as a through passage. Lobbies should be twice the depth of the car (Figure 11.2a). Modern control methods can maximize efficiency with collective calls either downwards or upwards or in both directions for the single lift or with groups, and can be programmed to resolve peak traffic movements, morning and evening.

Car and landing door configuration affect efficiency, the two panel, central opening pattern being the favoured solution. Four panel designs are needed for wider, larger cars. Asymmetric plans are more space-effective but slower in operation. The concluding illustration Figure 11.2 b demonstrates the restrictions placed upon core planning with a high rise commercial building. The typical floor print in the AT&T headquarters, New York, reveals the 'racetrack' layout around the central core, with the lift lobby serving two rows of cars, and the separation of service lifts. The space of the lobby is dictated by fire regulations and also by the space needed for the machinery room at roof level. If residential floors exist, these have bypass shafts and separate entries at street level. In developments of 50 or more storeys it is common for lift operations to be staggered, for example, the lower group to serve up to level 25, the upper group to run level 1 to 25 non-stop and then stopping for the remainder, whilst a pair of cars might run non-stop to the penthouse suite.

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