Zaha Hadid Architects - Striatus, an experimental 3D-printed footbridge
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Striatus, an experimental 3D-printed footbridge

Zaha Hadid Architects

Special Projects  /  Completed
Zaha Hadid Architects

Striatus is an arched, unreinforced masonry footbridge composed of 3D-printed concrete blocks assembled without mortar. The 16x12-metre experimental structure is the first of its kind, combining traditional techniques of master builders with advanced computational design, engineering and robotic manufacturing technologies. The names Striatus reflects its structural logic and fabrication process. Concrete is printed in layers orthogonal to the main structural forces to create a striated, compression-only structure that requires no reinforcement. Proposing a new language for concrete that is structurally informed, fabrication aware, ecologically responsible and precisely placed to build more with less, Striatus optimises the interrelated properties of masonry structures, 3D concrete printing (3DCP) and contemporary design; presenting an alternative to traditional concrete construction. Striatus is an unreinforced concrete structure that achieves strength through geometry. In arched and vaulted structures, material can be placed precisely so that forces can travel to the supports in pure compression. This presents opportunities to significantly reduce the amount of material needed to span space as well as the possibility to build with lower-strength, less-polluting alternatives. The funicular shape of its structural arches has been defined by limit analysis techniques and equilibrium methods, such as thrust network analysis, originally developed for the structural assessment of historic masonry vaults; its crescent profile encompasses the thrust lines that trace compressive forces through the structure for all loading cases. Steel tension ties absorb the horizontal outward thrust of the arches. Neoprene pads placed in between the dry-assembled blocks avoid stress concentrations and control the friction properties of the interfaces, echoing the use of lead sheets or soft mortar in historical masonry construction. Advanced discrete element modelling (DEM) was used to optimise the block’s stereotomy and to check the stability of the entire assembly under extreme loading cases or differential settlements of the supports. The bridge’s 53 3DCP voussoirs have been produced using non-parallel print layers that are orthogonal to the dominant flow of forces. This avoids delamination between the print layers as they are held together in compression. The additive manufacturing process ensures the structural depth of the components can be achieved without producing blocks with a solid section, hence reducing the amount of material needed compared to subtractive fabrication methods or casting. Striatus follows masonry structural logic on two levels. As a whole, the bridge behaves as a series of leaning unreinforced voussoir arches, with discretisations orthogonal to the dominant flow of compressive forces, following the same structural principles as arched Roman bridges in stone. Locally, on the level of the voussoir, the 3DCP layers behave as traditional brick masonry evident in the inclined rows of bricks within Nubian or Mexican vaulting. Unlike typical extrusion 3D printing in simple horizontal layers, Striatus uses a two-component (2K) concrete ink with corresponding printing head and pumping arrangement to precisely print non-uniform and non-parallel layers via a 6-axis, multi-DOF robotic arm. This new generation of 3D concrete printing in combination with the arched masonry design allows the resulting components to be used structurally without any reinforcement or post-tensioning. Circular by design, Striatus places material only where needed; offering a blueprint for building more with less and significantly reducing its environmental footprint. Built without reinforcement and using dry assembly without binders, Striatus can be installed, dismantled, reassembled and repurposed repeatedly. Lowering embodied emissions through structural geometry and 3D concrete printing (3DCP) to minimises the consumption of resources and eliminate construction waste. Placing concrete only there where needed, 3DCP minimises the amount of material required, while the low-stress, compression-only funicular geometry of Striatus enables the use of much lower-strength, less-polluting printable concrete. Striatus uses external ties to absorb the outward thrust of its arched shape, requiring only 10% of the steel used as embedded reinforcement within concrete. Unlike conventional reinforced concrete structures, Striatus is designed to be dry assembled without any binder or glue, enabling the bridge to be dismantled and reused in other locations. Its funicular design ensures the 3DCP blocks experience low stresses throughout their use, resulting in no loss of structural integrity. Striatus separates components in compression and tension, ensuring external ties can be easily accessed and maintained, resulting in a longer lifespan for the entire structure. By ensuring different materials are separated and separable, each component of Striatus can easily be recycled with minimal energy and cost. 3D printing also avoids the waste associated with single-use moulds. As component materials within Striatus remain separate and separable using mechanical connections rather than chemical glues or binders, a simple, low-energy recycling process is possible.


 216 mq
 Zaha Hadid Architects
 A project by the Block Research Group (BRG) at ETH Zurich and Zaha Hadid Architects Computation and Design Group (ZHACODE), in collaboration with incremental3D (in3D), made possible by Holcim


Zaha Hadid Architects (ZHA) redefined architecture for the 21st century with a repertoire of projects that have captured imaginations across the globe. Form and space are woven within the structure of their works that evolve from the surrounding environments. Receiving the highest honours from professional and academic institutions worldwide, ZHA is one of the world’s most consistently inventive architectural studios—and has been for four decades. These 40 years of research are inscribed within every project. Marrying innovative design with ecologically sound materials and sustainable construction practices, ZHA does not look at the disparate parts, but works to understand them as a whole to meet the challenges and aspirations of a new generation.

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