A number of tension piles
were needed to hold the building down and prevent it from floating away.
Providing additional structural mass, tension piles
, retaining walls and ground anchors are some of the solutions.
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.
The substructure is extraordinary, with tension piles
under the shallow north side and compression ones under the heavy south side to prevent the imbalanced loading causing the whole thing to turn over backwards.
A solution using secant piled walls, cantilevered during construction and propped in the final condition was evolved combined with tension piles
in the base to resist uplift.
Armstrong told Construction Week : "He (the engineer) has to install tension piles
that hold the structure down below the sea level, and then the perimeter walls constructed deep below the sea level that create this island which will be in place for many years.