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Stepped-back design for London exchange
The six above-ground floors of a £7 million international telephone exchange to be built on the bank of the Thames in the City of London will be stepped and set back to preserve lighting angles and to ensure that views of St. Paul's Cathedral from London Bridge are preserved.
The building will incorporate a riverside pro- menade, public walkways at first floor level and fire station. Each wall of the building will feature full-length air conditioning ducts clad in glass fibre reinforced polyster resin; these will form balconies at each floor level giving access for window clean- ing and other maintenance work.
A heavy in situ concrete frame will be used for the centre, resting largely on a 10ft. thick concrete raft. The remaining one third of the structure will be on concrete piles driven to a depth of more than 60 ft.
A major feature of the early stage of the project will be the construction of the 40ft. deep basement within a steel sheet pile cofferdam to resist water seepage from the Thames. The basement, which
will have walls 3ft. thick, will contain two sub- floors, including plant rooms, and a lower ground floor with car park, sub-station and reception area.
A concrete beam grid with a perimeter beam will be constructed at the first sub-floor level, 25 ft. below road level, and this will be used tem- porarily for propping the steel sheet piling. It will later become part of the permanent sub-floor.
Bored piles used as temporary support for the grid of beams will later be increased in size to form the main r.c. structural columns at 25 ft. centres. The columns will generally measure 6ft. x 5ft. and will be 17ft. high. Above this a system of twin columns on a 25ft. grid has been introduced to make it possible to provide slots in the concrete floors between pairs of columns and corresponding pairs of beams, giving full flexibility for the cen- tre's elaborate service runs.
Architects for the project are Hubbard Ford & Partners.
Development in prestressing steel
The proceedings of the symposium on 'Steel for prestressing' held by the Federation Internationale de la Precontrainte (International Federation of Prestressed Concrete) in Madrid in 1968 have now been published. Copies of the publication are avail- able from the Federation at Terminal House, Grosvenor Gardens, London, S.W.1, price £3.
The papers and discussions are of particular value and importance since they provide a compre- hensive review of some of the most important as- pects of both development and research in prestres- sing steel.
Topics dealt with include: Recent improve- ments in the manufacture and properties of pre-
London international telephone exchange
Far East BUILDER, May 1970
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