stressing cables were arranged between the precast units and the gaps con-
creted up. This system eliminated the difficulties of aligning ducts, threading cables and grouting up ducts.
The advantage that P.S.C. has over ordinary reinforced concrete where cracking cannot be tolerated brought P.S.C. into use in several structures from 1958 onwards. The first major project in which P.S.C. beams were used primarily for their crack-free properties was for the Tanglin Sewage Pumping Station, Singapore, designed by J.D. & D.M. Watson.
In 1965, prestressed concrete units were used again for the grit channels of pumping stations for the Toa Payoh Sewerage Scheme designed by the same consultant. Hume Industries were the successful tenderers in both instances.
In the Federation of Malaya. the P.W.D. concrete reservoir at Gun Hill, Seremban, was a major landmark in P.S.C. development. The circular tank was prestressed to keep concrete in compression.
Many other applications of pre- stressed concrete for its crack-free ad- vantages can be found in Singapore and Malaysia: the Butterworth Whar- ves project (Sir Wolfe, White Barry & Partners): water troughs for the Linggi Water Scheme. Negri Sembi- lan. (Binnie & Partners): prestressed piles for Shell Co.'s small craft har- bour, Pulau Bukom: planks for sewage sludge digestion tank roofs, (J.D. & D.M. Watson).
Post tensioned concrete is being used for the longer span bridges in Malaysia. The Parit Bridge over the Sungei Perak, designed by the Public Works Department, and the bridges over the Batu Pahat and Muar rivers designed by Steen Sehested & Partners, are two examples.
two
In the field of buildings, prestressed concrete has not been used to any sig- nificant extent, but with architects' specifications for longer spans, with higher buildings requiring lower dead loads, faster rates of erection being demanded and rising costs of labour, factory manufactured building units may one day be used in buildings.
The first signs of such a trend are becoming evident. One of the largest buildings in Singapore now under construction, Ming Court, (Kumpulan Akitek. architects: T.H. Chua & As- sociates, Engineers) includes several floors of Prestressed Concrete, and in Kuala Lumpur an interesting pre- stressed shell roof has been designed for a University Lecture Theatre to mention two examples.
The development of prestressed concrete in Malaysia and Singapore has thus been slow but sound.
The material has only come into use where its special properties have fully justi- fied the choice of prestressed concrete. Experience in the design and construc- tion has been gained and there is no doubt that the uses of prestressed con- crete will extend as economic patterns change.
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Prestressed Raymond piles for
Malayan East Coast bridges
Post-tensioned bridge over
the Sungei Perak at Parit
Special precast concrete beams for Singapore sewage pumping station
Far East Architect & Builder February, 1967