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World-beating cantilever lift succeeds at Dubai’s One Za’abeel

Rod Sweet

Engineers are celebrating the success of a record-breaking lift in Dubai that saw the main section of an 8,500-tonne cantilevered steel structure lifted some 100m above a busy, six-lane highway.

In a career-first for those involved, the cantilever was fixed to the two towers, still under construction, comprising developer Ithra Dubai’s One Za’abeel mixed-use scheme.

Called The Link, the 226m cantilever is claimed to be the world’s longest, higher than some skyscrapers if stood on end, and heavier than all the iron in the Eiffel Tower. 

It is just 15m shorter than the smaller of the two towers it connects.

Jutting 66m into thin air, it will house restaurants and shops and have an infinity pool on its roof, as GCR reported in November.

Jutting 66m into thin air, The Link will house restaurants and shops and have an infinity pool on its roof (Ithra Dubai)

The lift took place over 12 days starting with extreme caution on 18 August.

On that day the cantilever was raised a mere 10cm to check for cable stretching and to see how the buildings reacted to the strain. 
"The lifting process was incredible," said Dr. Fadi Jabri, an executive officer for Japanese engineering design firm Nikken Sekkei, which worked on the scheme’s design with WSP, the architect of record.
He said all work on site was halted so engineers could hear the buildings’ reactions.
A week later The Link was lifted another metre for observation, followed three days later by the final 100-metre lift.

On that day the cantilever was raised a mere 10cm to check for cable stretching and to see how the buildings reacted to the strain. 

"The lifting process was incredible," said Dr. Fadi Jabri, an executive officer for Japanese engineering design firm Nikken Sekkei, which worked on the scheme’s design with WSP, the architect of record.

He said all work on site was halted so engineers could hear the buildings’ reactions.

A week later The Link was lifted another metre for observation, followed three days later by the final 100-metre lift.

 

 

The towers were pre-cambered so that when the cantilever was attached they would deflect back to their true vertical position, according to Mace, the UK-headquartered firm that is providing project and programme management.
Developer Ithra Dubai said more than 110 special jacks and heavy-duty strand jacks were used for the operation, which was overseen by an international team experts.
Slid over the road
With a total area of some 470,000 sq m, One Za’abeel comprises two podium-mounted towers – 304m and 241m in height – straddling a traffic artery near the Dubai World Trade Center Exhibition Halls.
The Link was assembled on the towers’ podiums and was slid over the highway in six stages as new sections added to its length. Each slide necessitated the highway’s closure.
The size and complexity of the project led main contractor ALEC Engineering and Contracting LLC to use 4D modeling with Bentley’s Synchro instead of traditional planning techniques.

The towers were pre-cambered so that when the cantilever was attached they would deflect back to their true vertical position, according to Mace, the UK-headquartered firm that is providing project and programme management.

Developer Ithra Dubai said more than 110 special jacks and heavy-duty strand jacks were used for the operation, which was overseen by an international team of experts.

Slid over the road

With a total area of 470,000 sq m, One Za’abeel comprises two podium-mounted towers – 304m and 241m in height – straddling a traffic artery near the Dubai World Trade Center Exhibition Halls.

The Link was assembled on the towers’ podiums and was slid over the highway in six stages as new sections added to its length. Each slide necessitated the highway’s closure.

The size and complexity of the project led main contractor ALEC Engineering and Contracting LLC to use 4D modelling with Bentley’s Synchro instead of traditional planning techniques.

The One Za’abeel project in October 2019

Ms. Bayan Abdel Rahman, ALEC’s senior 4D planning engineer for the project, told GCR that this approach knocked 70 days off the programme thanks to clash detection and better scenario planning, and had saved $16m so far by giving clearer visibility into the structure and the schedule.

In one instance, The Link’s construction programme was reconfigured in six segments instead of seven, which removed one sliding operation over the road, cutting 30 days and $4m off the programme.
"Designing the world’s longest-occupied cantilevered building was an ambitious challenge in itself," said Nikken’s Fadi Jabri. 
"However, designing an offset cantilever between two towers, 100 metres above a busy highway, was a challenge of ingenuity and imagination none of us had ever faced before."
• More on One Za’abeel and 4D modeling here. 
Top image: The Link was raised just 10cm first to see how the buildings reacted to the strain (Ithra Dubai)

In one instance, The Link’s construction programme was reconfigured in six segments instead of seven, which removed one sliding operation over the road, cutting 30 days and $4m off the programme.

"Designing the world’s longest-occupied cantilevered building was an ambitious challenge in itself," said Nikken’s Fadi Jabri. 

"However, designing an offset cantilever between two towers, 100 metres above a busy highway, was a challenge of ingenuity and imagination none of us had ever faced before."

• More on One Za’abeel and 4D modelling here. 

Top image: The Link was raised just 10cm first to see how the buildings reacted to the strain (Ithra Dubai)

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