Four fully automatic 700 ft. per minute lifts are installed in the core and are controlled by a system with a built-in programme for peak traffic operations. This control is effected by turning a keyswitch on the master con- trol panel located in the ground floor lobby; one pair of lifts is then made to serve between ground and the eighth floor while the other pair serves be- tween ground and the upper half of the tower block.
Structural design
The structure is a conventional reinforced concrete frame supported on piled foundations.
Structural design was generally in accordance with BSCP 114 (1957), the Use of Normal Reinforced Concrete in Buildings, and BSCP 3, Chapter V, Loading. The specification called for a 28-day cube strength of 3,750 p.s.i. with less than one per cent probability of failure and the use of deformed alloy steel bars and welded steel mesh with 60,000 p.s.i. yield strength in all reinforcement, other than where it is nominal, throughout the building. Workability aids were used in both the substructure and the superstructure.
The substructure comprises a one
storey basement over the whole site except under the tower where the basement is two storeys deep. In view of the non-uniform subsoil conditions, the whole structure is supported on 60- ton precast reinforced concrete piles, 20 to 80 ft. long.
At an early stage in the course of the piling a masonry sea wall supported on timber piles was uncovered. This was removed in preference to re- designing the foundations.
The walls of the basement and sub- basement are 10 in. thick, and those of the lift pit 12 in. thick, excluding the concrete infill between the sheet piles. The basement floor thickness is 18 in. increased to 3 ft. 6 in. and 4 ft. 6 in. at pile caps.
Sub-basement floor thickness is 20 in., increased to 4 ft. 6 in. and 5 ft. at pile caps. The pile caps are integral with the floor slabs and are splayed out at 45 degrees in each direction at each cap.
The substructure was constructed in a cofferdam using steel sheet piles which were left in. As past records showed that the water table could be virtually at existing road elevation under flood conditions, the substruc- ture was water-proofed by means of a
dense concrete, careful site control, a 2 in. thick cement-based chemical grout membrane under substructure floors and partial grouting to the walls.
Details of the substructure and of the grout membrane were published in Far East Architect and Builder, July 1967.
Hydrostatic tests carried out several months after the completion of the membrane disclosed less than half a dozen damp spots under 20 ft. hydro- static head, mostly at construction joints, which were sealed by grouting.
There are no expansion joints in the substructure, which is not subject to large fluctuations of temperature. However, during construction great care was taken to minimize subsequent movement of the substructure by means of shrinkage joints, with time intervals of not less than seven days between the concreting of adjacent bays, and strict insistence on curing. The performance of the concrete sub- structure to date has proved that under similar local conditions, expansion joints are not always needed in 300 ft. long substructures.
The structural floor of the podium comprises 28 ft. span transverse ribs, 8 in. x 18 in. overall at 4 ft. centres
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MSA booking office; decor by Wong & Tung & Associates, Hong Kong
20
H
Far East BUILDER, May 1969