Rising Tide

Both an elevated and at-grade walkway, The Tide is a layered network of recreation, culture and wellness. The first phase of the project is 3,300 feet long, and features a linear public walkway, elevated gardens, pocket cafes and an architectural promontory overlooking the Thames River. Its distinct, elevated, landscaped islands are defined by unique trees and planting, and by their surrounding views and sounds. These elevated gardens are designed as clusters of steel structural supports that create elevated planter beds, containing soil and channeling both gravity loads and water down to the ground.

A PUBLIC SPACE STRATEGY

The Tide has to accommodate large movements of people along with the leisure and the social life of new residents, across roadways, vehicular arteries and ground-level areas. To do this, Benjamin Gilmartin, partner at Diller Scofidio + Renfro, New York City, and lead designer and partner-in-charge of The Tide, says 28 sculptural steel structures cluster and lean together as islands of mutual support, defining a layered landscape. “At ground level, their swaying legs shape vaulted portals and café pavilions. Above, they create an infrastructure for quieter overlook gardens and support the elevated islands of the first phase. Operating more than structure, they house all the systems for lighting, electrical distribution, data, drainage, water supply and soil. They’re fully integrated living pieces of architecture above and below. The undersides feature porticoes and column legs that aggregate and lean on each other, swaying and bending to frame pathways.”

Diller Scofidio + Renfro worked in design collaboration with Neiheiser Argyros, London. “The islands are connected by prefabricated steel bridges forming a continuous (almost) 8-foot-wide path with spans up to 86 feet,” says Ryan Neiheiser, director, Neiheiser Argyros. “Every support and bridge is composed of welded plate steel inner ribs and outer skins forming an aircraft wing-like structure that is lightweight and minimizes impact to the London Underground station box directly below.” Mace Group, London, was the general contractor for the elevated portion; and Mayim, London, was the contractor for the ground-level portion. The steel canopy fabricator was Urban Street Design, Nelson, England.

A LAYERED LANDSCAPE

Diller Scofidio + Renfro designed a layered landscape connecting an archipelago of cultural and social spaces. This elevated pedestrian landscape network had to be supported by ground plane circulation. The metal island and bridge structures touch down to station tunnel limitations below, or thread their way among exhaust towers, exit stairs and mechanical plants. “These diversions offer some very interesting moments along the path, where you can feel embedded within the infrastructure, not just physically but also acoustically,” Gilmartin says.

Lightweight prefabricated steel was chosen forits inherently high strength-to-weight ratio that ensured each island would be structurally robust yet remain light enough to be transported and erected swiftly onsite. “Sheet steel is also a more cost-effective material than either precast or in-situ concrete in producing unique variants of a core design-type—a critical factor, given the divergence in island forms,” Neiheiser says.

“Furthermore, by utilizing a thicker gauge for the outer envelope, this 10- to 20-mm surface could double as both architectural finish and load-transmitting element, negating the need for a duplicative layer of cladding, and instead creating a structurally efficient, fully mobilized stressed-skin assembly. This system has the additional benefit of being sealed watertight against the harsh riverside environment.”

Neiheiser says this effect achieved is “sculpturally expressive” with the columns formed almost entirely of economical planar surfaces. He explains only one type of single-curved surface is present in the flare that efficiently blends between the radically different upper and lower-column cross sections. In addition to the islands, this concept was repeated for the link bridges. “The result is a simple external form and elevation that are a pure expression of the bending moment forces acting on them under uniform loading, supported by an efficient internal skeleton of longitudinal and transverse stiffeners,” Neiheiser adds.

The design of the structural elements was a special architectural and structural collaboration with London-based structural engineer AKT II using parametric software to maximize material efficiency and minimize fabrication complexity. The London Underground station box, which the Tide stands atop, has strict weight restrictions. Installing lightweight and prefabricated steel elements minimized both unnecessary force to the station below and erection time.

The steel elements were manufactured, installed and fabricated by Cimolai Group (UK) Ltd., Cambridge, England. “Cimolai supplied 28 sub-islands and seven linking bridges and a stair, for a total of approximately 660 tons [of material] made in steel with curved surfaces and with architectonical finish,” says Federico Siriani, director at Cimolai. “All sub-islands were transported as a whole piece, and all fabrication was completed in Italy with full control of the geometry.

Barges transported this on the Thames to the Greenwich Peninsula, and pieces were moved to site by self-propelled modular transporters for subsequent installation. Cimolai also supplied and installed glass balustrades, together with handrails and other stainless steel metal works. Cimolai worked with a relative thin skin plate of 10 mm to reduce to an acceptable level the distortion generated by the welding of the project’s internal stiffeners and joining elements.” Neiheiser says the end result of all of this is, “An integrated architectural and structural expression without superfluous cladding.”