July_1967 — Page 35

SINGAPORE

CIVIL ENGINEERING AND PUBLIC WORKS

WATERPROOFING THE SUBSTRUCTURE OF MSA HEADQUARTERS

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'HE site of the Malaysia-Singapore Airlines Headquarters Building, Robinson Road, Singapore, is approx- imately a rectangle, 300 ft. long and 108 ft. wide. At one end is Crosby House a reinforced concrete framed building on piles, and at the other the site of the proposed Bank Negara Building. The long sides are flanked by Robinson Road and a service road, respectively.

The structural frame of the build- ing is of reinforced concrete. The superstructure comprises a three-storey podium, with a tower block at one side rising 15 storeys above the podium. The substructure comprises a basement car park occupying the whole area of the site, and a sub-

*This article is based on a paper "The Waterproofing of the Substructure of the Malaysian Airways Headquarters Building, Robinson Road, Singapore", presented by Y. S. Lau and H. S. Ho of Lau, Berger and Associates, and G. M. Wheat of Treego Trading Ltd., to the Symposium on Quality of Local Concrete held re- cently in Kuala Lumpur by the Cement and Concrete Association of Malaysia.

Far East Architect & Builder July, 1967

by Y.S. Lau, H.S. Ho and G.M. Wheat*

basement about 100 ft. by 100 ft. un- der the tower block.

The building is supported by end bearing precast reinforced concrete piles between 20 and 80 ft. long. Past records revealed a high water table with a maximum elevation of 106.5 ft. at flood which is only about 6 in. be- low parts of the adjacent roads. This led to a decision to construct the whole of the substructure in a steel sheet pile confferdam. The absence of construction delays in the substructure on account of ground water fully vindicated this procedure.

In order to utilise as much of the site area as possible for the basement. the substructure walls had to be cast against the peripheral steel sheet pil- ing, which was left in. A cost analysis by the quantity surveyors showed that the savings in capital cost in ex- tracting and selling the sheet piles would have been negligible and would

have been largely off-set by loss of time in constructing the substructure.

The walls of the basement and sub- basement are 10 in. thick, and those of the lift pit 12 in. thick, excluding the concrete in-fill 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. The sub- basement floor thickness is 20 in., in- creased 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.

Water Proofing Methods

Present day opinion on the best method of waterproofing basements is divided. There are two main ap- proaches to the problem, the first de- pending on the impermeability of the structural concrete, and the second

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