June_1970 — Page 7

world news

Qantas to build twin towers

The A$50 million development of a complete city block will provide Qantas with a new head- quarters and Sydney with two skyscraper towers to dominate its skyline.

Preparation of the site near the southern end of the Sydney Harbour Bridge is well advanced and construction work on a huge underground com- puter complex will begin this year. Work on the first of the two towers will start in 1971 and will

Twin-tower Qantas Centre

QANTAS

be completed late in 1973. The building will rise through 50 levels to 607 ft. The second tower will not be started for several years.

More than two acres of open space, plaza and walkway on different levels will be created at the foot of the two towers, bounded by George, Gros- venor, Lang and Jamison Streets.

The first and larger tower will rise from a podium and will be supported between four ver- tical white concrete columns each 60 ft. wide and

5ft. thick. Huge trusses will be attached to these columns, with the floors suspended on cables from the trusses. This will allow open floor plans unclut- tered by internal supports.

When construction of the columns starts in 1971, it will be one of the largest building concrete pourings in Australia. The columns will serve a dual purpose as they will shield the buildings from the hottest angles of the sun.

The distinctive construction of both buildings should also give them an indefinite life. The sur- faces of all floors can be lifted and service ducts opened. This means that if new methods are de- vised for handling certain situations, new equip- ment can be installed with a fair degree of ease. It also means there can be a system of preventive maintenance so that the miles of wires and pipes can be kept under constant surveillance for repair or replacement.

Planning to build the towers on one of the most exposed positions in the city area of Sydney has resulted in an interesting study being made of the effects of wind not only on the towers but on other buildings in the area. To make the study, a complete model of the northern end of the city as it will be in 1973 was constructed in England and exhaustive wind tunnel tests were made.

Already it has indicated that there will have to be some sort of wind deflecting system to make the public areas between the towers comfortable. The architects, are investigating a system of auto- matically operated deflectors which emerge as the wind velocity increases.

New tunnel lining designed

Tunnel construction is likely to change because of work at the Building Research Station in Britain the first change of any consequence for about 100 years. All this time, bolted cast iron linings have been used for underground railway systems. They were quite satisfactory. But, a few years ago, the BRS decided to look at the performance of these linings and found that they were not as logical or economical in design as they might be. A new design has now been produced.

It has 12 segments to one ring, instead of the old six and the segments are ductile cast iron. The weight of each segment is about a quarter of the ordinary one, so the total weight of a ring is cut by half. The ductile iron has high impact resistance, so that it can stand up to far tougher treatment on site without breaking. It can be made automatical- ly and there is no need to machine the bearing surfaces.

The linings have been checked against each other in a tunnel made for the new Victoria Line in London, particularly to see what happened when another tunnel was driven alongside the first one, only 0.65 metre away.

The ductile iron rings are more flexible, but on the other hand the BRS team thought that rigidity

Far East BUILDER, June 1970

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