Capital Gate

A landmark tower among landmark towers, Capital Gate is the 35 storey focal point of Abu Dhabi's Capital Centre, a mixed use development supporting the Abu Dhabi National Exhibition Centre (ADNEC). In June 2010, it was certified by Guiness Book of Records as the furthest-leaning manmade tower in the world. We were appointed as specialist consultant by lead engineer and architect RMJM to advise on construction.

Unusually organic in form, the 160m tower is constructed of a steel diagrid with a partially prestressed elliptical concrete core. The lean is of the order of 18 degrees and the structure has a massive eccentric deadweight. Plant is housed on floors 1 and 17. Floors 2-16 accommodate commercial office space and a hotel is accommodated on the upper floors. Construction commenced September 2007.

Using various pieces of software, including ETABS and DIANA, our structural specialists undertook a series of analysis and development tasks. We also developed new high-level data processing software in order to assemble construction sequence simulation data.

A finite element model of the tower for each construction phase was built, with non-linear time dependent analysis, including creep, shrinkage and maturity related strains. We calculated the 3D pre-cambered geometry needed to achieve the intended position of the tower, which is critical to the operation of the whole building, especially its lifts. In addition, we designed the vertical post-tensioning of the concrete core to control cracking so that the structural behaviour of the tower is predictable.