July_1971 — Page 19

Detail of slipformed core showing starter bars for slabs

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frame were both reinforced for 60 per cent wind load each giving in effect an increased factor of safety on ultimate strength.

Slabs were reinforced for the addi- tional moments and spandrel beams designed to take the torsion resulting from the wind transfer.

Due to the permissible 25 per cent increase for wind stresses, the peri- pheral columns needed no additional reinforcing other than that provided to carry the gravity load.

Member Sizes

All core walls were slipformed and only one change in wall thickness was considered desirable. The main struc- tural core wall is 12 in. thick from raft foundation to first floor level and 10 in. for its remaining height. Internal walls are 9 in. thick for lower floors and 6 in. thick above first floor level.

As a constant wall section was maintained, concrete strength and reinforcement were varied to give maximum economy.

Annulus slabs are 8 in. thick while slabs within the core are generally 4 in. thick. There is no screed on the slabs, and the services are contained within the 8 in. depth. The reinforcement in the annulus slabs was varied with height to conform to the pattern of radial moments induced in the salbs due to wind transfer.

The tower is founded on a total of 21 caissons; each of the twelve co-

Far East BUILDER, July 1971

lumns being supported directly by a 5ft. diameter caisson with the central core supported on nine caissons vary- ing from 4 ft. to 7 ft. in diameter. A circlar raft is used to transfer wind moment taken by the core to the outer ring of caissons. By taking into account the proportion of wind load resisted by frame action considerable savings were made in the raft founda- tion.

Caissons were hand excavated and extend down to bedrock approximate- ly 60 ft. below ground level. Concrete of 4500 p.s.i. strength was used.

Podium

It was desirable to keep the num- ber of obstructions in the car parking to a minimum and to maintain the same floor to floor height as for the tower. The number of columns was reduced by using a system of prestress- ed concrete beams and slabs.

The choice of prestressed construc- tion enabled the structural depth to be kept to the absolute minimum and spacings to be increased to a comforta- ble parking grid.

The post-tensioned beams are two span continuous units with a cantilever span at each end and are haunched at supports.

Each column is founded directly over a 3 ft. 6 in. diameter caisson to carry the load to bedrock. Caissons supporting the podium were cast in 3000 p.s.i. strength concrete.

Core with climbing crane above and floor surrounds during construction

The pool is of reinforced concrete construction and is suspended above general service rooms. The whole pool structure is founded on a system of intersecting strip footings.

Contractors

Total estimated cost of the project was HK$18 million.

Gammon (HK) Ltd. were the main contractors. Sub-contractors included:

Jardine Engineering Corp. Ltd. - Schindler lifts, air conditioning, elec- trical installations and pool filtration equipment

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Dodwell & Co. Ltd. plumbing and Crittal metal windows

Innis & Riddle Ltd. - American Standard sanitary fittings

Burgor (HK) Ltd. fire detection equipment

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Acconci & Son marble works Bollore Co. Ltd. woodwork Tai Wah Ltd. - kitchen equipment Petman Ltd. — aluminium works Lee Nam Co. - painting and wall. papering

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vene-

Young's Home Decorator tion blinds and curtain tracks Freda Carpets - carpeting Shewan Tomes Ltd. - hardware E. Line King - waterproofing Poly Fibreglass Corp. imitation

marble

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Showerfold

Honest Trading Co. aluminium shower partitions.

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