Tall orders: High rise construction

High-rise towers continue to climb across the globe as potent symbols of emerging nations growing economic power. But how high can they go, and how green are they? Richard High reports.

Wherever you look at present iconic, high-rise projects are springing up across the globe: China, the US, the United Arab Emirates (UAE), Korea and Russia are all looking to demonstrate their economic prowess by building new and often dazzling structures.

In Shanghai the Kohn Pederson Fox designed 421 m high Shanghai World Financial Center, expected to be the world's second tallest building when it is completed next year, will be home to scores of the world's most powerful companies, and a potent symbol of China's growing financial muscle.

Elsewhere in Asia, Korea's Seoul and Incheon are going head-to-head to build enormous towers, symbols of their own rising prosperity. In Incheon, the US$ 3 billion, 613 m high Songdo Incheon Twin Towers will be the centerpiece of a 53 km² urban development, called New Songdo City. Not to be outdone Seoul is planning its own symbol to economic might, the 600 m high Yongsan Landmark Building.

Cash rich following South Korea's economic takeof, Incheon and Seoul are being joined in the building rush by Busan, where two skyscrapers of more than 100 storeys are under construction, including the 560 m Millennium Tower World Business Centre.

In the Middle East, Saudi Arabia's Mecca and the UAE's Abu Dhabi, Dubai and Qatar's Doha are current hot spots. In May this year Abu Dhabi Municipality launched a US$ 7.1 billion project to construct 347 high-rise towers, which are expected to house over 50000 people.

Elsewhere, Moscow's Russia Tower is expected to be 610 m high when complete in 2011, while New York's Freedom Tower, which will occupy the former site of the World Trade Center (WTC), will be 541 m high, In Chicago the Santiago Calatrava designed Spire will top 600 m, easily passing the 415 m high Trump International Hotel and Tower, also under construction in the city, while Karachi's Port Tower Complex is expected to rise to 593 m.

After 9/11

According to Hyder Consulting's director of structures Burj Dubai, Dr Andy Davids, an “interesting outcome” of the 9/11 attacks “was that money was driven out of the substantially unstable stock markets into the traditionally more stable property market. This flood of funding [is fuelling] many residential developments, particularly high-rise properties,” he added.

Dr Davids told IC that the attacks of 9/11 left a series of “place markers” in the minds of the tall building design community.

“The first is robustness, which is broadly the ability of something we design/build to be able to survive an event or use for which it was clearly not intended. the second was the ability to get people out of a damaged building, and the last is the way in which a structure collapses. Does one thing lead to another, with total destruction the inevitable outcome, or can structures be induced to collapse in a difierent, more limited way?”

The WTC collapse, said Dr Davids, “was a clear and public demonstration of an unzipping or progressive collapse, which could have only one outcome”. the design of any structure, therefore, said Mr Davids, to have a reliable resistance to progressive collapse remains a challenge to the tall building community.

However, he told IC the tragic events of 9/11 “do not seem to have much of a lasting effect upon the nature of tall building design in the UAE. Residential, tourism and travel are strong, and the key work of building a nation goes on apace. Tall iconic buildings are continuing to play their part in the national endeavours.”

Indeed, the UAE has dominated the high-rise sector over the past few years. there are so many high-rise projects currently under construction across the UAE that iC's sister magazine, International Cranes & Specialised Transport (IC&ST), estimates that of the 125000 tower cranes currently in use around the world 30000 are working there, with 4800 in Dubai alone.

Dominating Dubai's high-rise sector is the Burj Dubai. Designed by Adrian Smith during his time at Skidmore, Owings & Merrill (SOM), the building, mooted to be over 800 m high when completed next year, has been described as part of Dubai's “nation building” process by Dr Davids.

With work on the concrete core almost complete developer Emaar is planning a New Year's Eve 2008 launch for the tower (see IC news 5 August). However, construction has not been without its problems.

Milestones

In March 2006 construction workers rioted at the 2 km², US$ 20 billion Downtown Dubai site, of which the US$ 4 billion Burj Dubai is just part, in protest against low pay and alleged mistreatment. While the men quickly returned to work, after causing over US$ 1 million worth of damage, and the leaders of Dubai moved to improve pay and conditions, unrest has continued throughout the Emirate.

Then in November last year, with the building having reached 87 storeys and the concrete core standing at 300 m, reports of delays to the cladding and problems with some of the concrete floor slabs began to emerge.

Difficulties in sourcing cladding followed the collapse of Switzerland-based Schmidlin in February and were originally blamed by the Besix, Arabtec Samsung joint venture for the lack of progress. Cladding eventually arrived in June this year, made by China's Far East Aluminium Works Company, and work is now “progressing”, according to developer Emaar.

At the time a project insider blamed other reasons for the delays, including design changes to the height. “There are [also] concerns over the structural integrity of the slabs. Certain calculations are being called into question,” said the source.

Speculation in the regional media said slabs throughout the structure were being reinforced using carbon fibre. This followed news slabs on the lower floors had been subject to significant deffections and had been repaired using external steel reinforcement.

At the time, Emaar's project manager at the Burj, Greg Sang, told IC, “the timetable has been effected by the collapse of Schmidlin. We're a little bit behind but we expect to put in place measures that ensure we're on track to meet our original completion date.

“Normally you'd be looking to do a floor in three to four or perhaps seven days depending on the technical requirements of the job, we're still working on the details but I expect to meet the dateline we've set with an accelerated installation timetable,” said Mr Sang.

News from the project has not all be doom and gloom though. In July it was announced it was now “the tallest building in the world”, having passed 512 m that month. the previous record holder, Taiwan's 508 m high Taipai 101, had held the record since it opened in 2004.

At 141 storeys the Burj Dubai also had more storeys than any other building in the world. On the 20 August Emaar reported the Burj Dubai's height to be 536.1 m, with 146 completed floors, surpassing Chicago's 527 m high Sears Tower.

The final height of the concrete core is expected to be 575 m. Topping this will be a steel spire, which is expected to raise the final height beyond the 800 m mark, although this could be exceeded as Emaar tries to thwart any attempt to stop the building from being the tallest building in the world for some considerable time.

Still to come as IC went to press is news of a another world record. Germany's Putzmeister has supplied a combination of concrete pumps, a sophisticated delivery line system, non-ballasted stationary booms which should see sub-contractor Unimix clinch the world record for the highest vertically concrete pump ever, 570 m, later this year.

Rivals

There are several other “mega-projects” in various states of planning and construction that could vie for the title of “the world's tallest structure”. One potential competitors is a proposed tower only 50 km from the Burj Dubai site.

Al Burj (the Tower) is being developed by Emaar's Dubai-based rival Nakheel Properties, who are also keeping the project's final height tightly under wraps. Meed.com recently reported that this tower's projected height would be around 1200 m with at least 200 storeys, although Nakheel CEO Chris O'Donnell has denied the story.

Speaking to local press earlier this year he said, “Height isn't everything and biggest isn't best. What you have to do is come up with a building of real relevance. Look at the Sydney opera House or Tower of London, they aren't the tallest, but they are iconic.”

Another proposed supertall tower, the Murjan Tower in Manama, Bahrain is planned to be 1022 m tall with 200 floors.

It is currently being designed by Danish firm Henning Larsens Tegnestue.

Another potentially competitor is the proposed 1001 m high Mubarak al-Kabir Tower, to be built in Kuwait as part of a huge development called Madinat al-Hareer (City of Silk), which also includes an Olympic standard stadium, apartments, hotels, and retail facilities, although the project may take over 20 years to complete.

Green shoots

With so many tall towers either under construction or planned worldwide concerns are being expressed over how green many of these developments are. According to David Strong, head of the UK's Building Research Establishment, modern skyscrapers are a “depressing statement of man's arrogance over nature.”

Speaking at Nightingale Associates’ sustainability conference earlier this year, Mr Strong decried the “extinction” of architecture and environmental design, saying a “green curriculum” had “never been needed more”.

A response of sorts has come from the UAE. In July it was announced the Emirate is to pilot a green building rating system later this year to measure the environmental sustainability of buildings in design, construction and operation, according to Gulf News.

Based on the US Leadership in Energy and Environmental Design (LEED) rating, it will be adapted to suit the UAE climate and property market by the Emirates Green Building Council.

The system is likely to be formally introduced following a six to 12 month trial period, according to Kamal Azayem, senior engineer at the Dubai Municipality building department. “the rating system will be voluntary, but it will provide a reference point to gauge a building's sustainability,” said Mr Azayem.

In practical terms a building's green credentials should be easy to judge. About to start construction in Miami, US, the Brickell Financial Centre will in essence be just another massive block of glass and steel, but its glass will be “low-emissive”-a coating will allow light to filter through but will block out solar heat.

Elsewhere, “punch” windows will be set in 300 mm from the exterior to provide physical shading. Its cooling system will circulate chilled water throughout the building rather than use an “ineficient” air-conditioning system.

Low-flow urinals and dual-flush valves will cut down on potable-water use, while large cisterns will collect rain water for use throughout the building, with any excess being fed back into the city's water system.

While environmental concerns push the green development envelope, Hyder's Dr Davids told IC the future of tall building development could be helped by borrowing technology from engineering very small objects.

“Organic systems have the ability to multiply and build themselves into objects thousands of times larger than their fundamental unit in a very short duration,” he said. Some combination of organically multiplying material being crafted by embedded nano-technology machines, argues Dr Davids could push the development of tall building even higher.

However, he believes the limit to “our craft” as engineers and architects is “only that which is passed to us by our imagination. Given a task, we will eventually find a way to do it, although some may retire along the way.