DeSimone’s recipe for towering structural success
Consulting engineers behind CW’s 2015 Tower Project of the Year explains Al Maryah Tower’s marvel
DeSimone Consulting Engineers is firmly grounded in the US construction industry, so it was little surprise to see them in the running for a number of the 2015 Construction Week awards, but it was not past prestige but present prowess that clinched the recent win of the Tower Project of the Year.
The 34-storey Al Maryah Tower, located on Abu Dhabi’s Al Maryah Island, is not so much remarkable for what has been achieved on the outside, but for the Tardis-like miracle of its internal structure.
Through a combination of 12m spans cast in post-tensioned concrete and the resulting column-free interiors, the building has achieved a remarkable working efficiency off its footprint, while also adhering to a one Pearl Estidama rating.
“The efficiency of the building is 85%,” explains Ahmed Osman, managing principal at DeSimone Consulting Engineers. “You don’t find this anywhere: the columns are much more discreet than in any other tower you will see in the UAE.
“The architect, GP, was very demanding, but we love working with them – because it pushed us beyond our normal performance. We’re very happy with the final result.”
Osman continues: “Architects love column-free open space and we love that ourselves. We hate seeing a column in the middle of a beautiful lobby. This is a challenging task for engineers, but it is also the way to go: this is how you tell a good engineer from a not-so-good engineer.”
The basement of the tower also plumbed the depths of Al Maryah Island, despite the adjacency to the sea and the extreme hydrostatic pressure from the water table in the underlying substrate.
Osman notes: “It was a 22m-deep excavation – probably the deepest excavation in Abu Dhabi – with six basement levels. As Al Maryah is a semi-artificial island, the hydrostatic pressure made that very challenging.”
However, with aggressive values from the geotechnical expert Langan, DeSimone was also able to rely on purely tension piles and reduce the thickness of the raft saving significantly on the concrete.
Osman explains: “It relies on the entire footprint to push against the raft; not just the pins of the piles with the raft spanning between the piles – where you end up with stresses in between the piles.
“Al Maryah Tower uses less material and less reinforcement. The raft is 1m thick and only 2.25m thick under the columns, while in terms of the reinforcement we’re talking 80kg/m3 – which is very light.”
And while many of the features of Al Maryah Tower may be unique, ambitious design is nothing new to DeSimone, which, since opening an office in Abu Dhabi in 2008, has also engineered structures such as the Sheikh Khalifa Mosque in Al Ain entailing a 90m-span dome wrought in structural steel.
Osman quips: “We don’t just do towers. In a value engineering exercise for Ghantoot Contracting on Saadiyat Island, we saved 65% on the reinforcement in one of the elements – so they are happy.”
Commenting on the project’s recent win at the Construction Week awards, he adds “We have won a lot of awards, but this one is special because it is about construction, and we really believe that it is all about construction; not just design – the two go hand-in-hand.
“As a company, we’ve been in business for almost 50 years – but after eight years of hard work in the UAE, it is very rewarding to now be receiving awards for the projects that we have done in the Middle East.”
Now handed over to the client, Al Hilal Bank, Al Maryah Tower was built by UAE contractor Al Fara'a, while the consulting engineer for the MEP was ESD.