Typical of Asian construction, the towers are built essentially of concrete. And symbolic of the country's Malay Islamic culture, architect Cesar Pelli designed each building as an eight-point star with a repetitive scalloped pattern on the curtain wall. Between each pair of points is a curved bay.

Each tower has about 2 million sq ft of office space (ENR 1/15/96 p. 26), but the project's usable floor space was increased by 43-story, cylindrical buildings attached to each tower. A two-level, 193-ft steel girder "skybridge" links the towers at the 41st and 42nd floors and serves as a fire exit. Two V-shaped, tubular steel legs rise from the 29th floor of each tower to support the bridge at mid-point. The ends of the bridge girders rest on sliding bearings that allow the towers to move as much as 10 in.

Each of the towers has an outer ring of 16 columns that are about 8-ft dia each made of 10,000-psi concrete that form a 150-ft-dia circle. The columns taper as they rise and slope inward to accommodate setbacks. At each level, the ring of columns is connected with a haunched ring beam. Lateral loads are shared by the columns and the 75 x 75-ft concrete core through floor diaphragms. The floors are composite metal decking and steel infill beams. Each tower stands on a 14.5-ft-thick concrete mat supported on 85 concrete friction piles, some as deep as 400 ft. Each mat contains 17,500 cu yd of concrete and was cast in a single, 50-hour pour.

Although the two Petronas towers are identical, they were built by different contractors. Tower Two's shell and core, as well as the sky bridge were built under a $200-million lump-sum contract by a joint venture of two Korean contractors: Samsung Engineering & Construction and Kuk Dong Engineering & Construction with Malaysia's Syarikat Jasatera Sdn. Bhd. Tower One, which cost several million dollars less, was contracted to a consortium of Hazama Corp. and Mitsubishi Corp. of Japan; J. A. Jones Construction Co., Charlotte, N. C.; and mmc Engineering & Construction Co. and Ho Hup Construction, both Malaysian. The Tower Two contractor claimed a concrete pumping record, raising concrete 1,246 ft in one lift. Both tower contractors used self-climbing forms for columns, core and beams. Thornton-Tomasetti Engineers, New York, was the structural engineer, with Lehrer McGovern (Malaysia) Sdn. Bhd., an arm of Bovis International, London, serving as project manager. The Petronas Towers will be surpassed in height soon by Shanghai's World Financial Center.

NEWS IN BRIEF 1995-1996

An Industry in Mourning
On April 3rd, 1996, a plane carrying some of the construction industry's most prominent figures crashed in the hills of Croatia. The loss of six top industry executives, Commerce Secretary Ronald H. Brown, and 28 other corporate and government officials, stunned construction and engineering firms nationwide. The officials and industry executives, all of whom had tremendous influence on the construction and engineering industries, were on a mission assembled by Brown to begin the process of rebuilding the war-torn Balkans. Brown had organized other similar missions in the past to advance business for U.S. firms. Many industry executives believed he was one of the best government promoters ever of U.S business abroad and an outstanding spokesman for u.s. firms overseas. (ENR 4/15/96).

Olympic Stadium's Fatal Design
A huge miscalculation in the design of Atlanta's Olympic stadium caused the collapse of a lighting assembly. The accident killed one worker. The structure gave out as two workers attempted to wedge apart canopy trusses. The bottom chords of all three canopy trusses buckled at the column connection, the middle truss was the most overstressed. A spokesman for the the Atlanta Stadium Design Team confirmed that the assemblies weighed about 16,500 lb, which was 10,000 lb more than was assumed in design. The designers admitted that the assembly weighed about five tons more than its cantilevered trusses were designed to support. (ENR 4/10/95).

Bridge Over Canadian Waters
The Northumberland Strait Crossing, later known as Confederation Bridge, was to be the first fixed link between mainland New Brunswick and Prince Edward Island. Constructing the $500-million, 12.9-kilometer-long bridge in a tight time frame with its precast concrete cantilever spans as heavy as 7,500 tonnes and as long as 197meters was a challenging task. The crossing's forty-three 250-m spans could be erected during 34 weeks out of each year because of frigid weather conditions. Two precasting yards were built and $15 million of formwork was installed. A $16-million jetty was built to move components to the bridge site, and specialized lifting equipment was imported. A floating crane carried precast parts from yard to strait for installment in the 11-kilometer main span (ENR 10/16/96).