...low-carbon footprint achieved by using a cement replacement and an on-site batch plant to eliminate truck deliveries. Reinforcing steel is specified with over 95% recycled content and structural steel with 60% minimum recycled content.

The headquarters design team contributed directly to the master spec for various products as well as systems, including wind-cone performance, underfloor air distribution and optimization of the photovoltaic products and positioning.

The complex has two major integrated but structurally independent, assemblies that share a common podium: the concrete office blocks and the steel PV-support trellis and its wind cones. The independence of the two systems will give the base-building contractor the option of starting either assembly first, says TT’s Sinn.

There are two, seven-story office blocks. Where the floors are punctured by the 51-m-tall cones, made of painted, hollow pipe sections, openings are framed by concrete columns sloping to match the profile of the cones. Curved ring beams are used at each floor opening to stabilize the sloping columns.


One of the project’s big challenges was to prove to local authorities that the 7,500-ton steel frame did not need fireproofing, says Sinn. This was demonstrated with the help of fire protection engineer RJA, which created different fire scenarios to determine a fire’s impact on steel strength even if the sprinklers did not work, says the engineer. That, combined with high-temperature structural analysis, showed that “we could lose practically half a cone” and all the others would keep the trellis from falling in, says Sinn.

The geometrically identical cones have a belled form, shaped by a diagrid frame of hollow pipe sections. Diagrid members are straight pieces; horizontal rings are curved. The 325-mm-dia pipes have various wall thicknesses depending on structural requirements. The base of each cone is 27 m in diameter, while the topmost ring is 7 m in diameter.

The trellis has an upper, flat mesh surface and a lower, wavy mesh surface. A section on the lower trellis has been dubbed “the peel” because it flares out from each cone 26 m above the base of the cones (see drawing). The peel section is then organized on a repeated 31.5-m square module in plan. The rest of the lower trellis consists of a diagonalized mesh of steel pipes attached to the perimeter of the peel, forming a checker-board pattern. Together the peel and the mesh surface at the lower trellis brace the bottom chords of the trellis trusses, which form the waved pattern.

Cantilevered trusses with bottom chords that follow the wavy profile of the lower trellis connect lower- and upper-trellis surfaces. Truss depths range from 1.3 m to 15 m at the root of the peel. With a maximum cantilever length of 57 m, the trusses are designed to limit the frequency at the tip to prevent adverse fluttering effects from wind action, says TT.

Each cone receives eight trellis trusses at equal spaces along its circumference. The top chords are composed of 450-mm-dia pipe sections and are braced at 11 m on center to create a horizontal platform for the PV-support grillage.

Sinn says there is a complicated joint at which the cone continues up and the wavy surface diverges. In this case, a steel casting will join the several members.

For constructibility and economies of scale, all parts of the headquarters building, designed using building information modeling, were developed to maximize repetition and modularity. For example, because the trellis and the concrete building are independent of each other, the trellis can be built before the concrete building and act as a shade for the workers. “It’s an option” for the contractor, says Sinn.

Jalayerian speaks for his project colleagues when he says he fully embraces the demands that the client Masdar has put on the design team. “I think it’s wonderful,” he says. “It’s aggressive, and it’s progressive.”