Page 18 - Designing Ways 247

3D PRINTING

Striatus

An arched 3D-concrete-printed masonry bridge

triatus is an arched masonry Exhibited at the Giardini della geometry. Concrete can be considered
footbridge composed of 3D-printed Marinaressa during the Venice an artificial stone that performs best
Sconcrete blocks assembled without Architecture Biennale until November in compression. In arched and vaulted
mortar or reinforcement. The 16 x 2021, Striatus has been developed by structures, material can be placed
12 metre footbridge is the first of its the Block Research Group (BRG) at precisely so that forces can travel to the
kind, combining traditional techniques ETH Zurich and Zaha Hadid Architects supports in pure compression. Strength is
of master builders with advanced Computation and Design Group created through geometry, rather than an
computational design, engineering and (ZHACODE), in collaboration with inefficient accumulation of materials as
robotic manufacturing technologies. incremental3D (in3D) and made possible in conventional concrete beams and flat
by Holcim. floor slabs. This presents opportunities
Proposing a new language for concrete to significantly reduce the amount of
that is structurally informed, fabrication material needed to span space, as well
aware, ecologically responsible and as the possibility to build with lower-
precisely placed to build more with strength, less-polluting alternatives.
less, Striatus optimises the properties of Striatus’ bifurcating deck geometry
masonry structures, 3D concrete printing responds to its site conditions. The
(3DCP) and contemporary design; funicular shape of its structural arches has
presenting an alternative to traditional been defined by limit analysis techniques
concrete construction. and equilibrium methods, such as thrust
The name “Striatus” reflects its network analysis, originally developed
structural logic and fabrication process. for the structural assessment of historic
Concrete is precisely printed in layers masonry vaults; its crescent profile
orthogonal to the main structural forces encompasses the thrust lines that trace
to create a “striated” compression-only compressive forces through the structure
structure that requires no mortar or for all loading cases.
reinforcement. Steel tension ties absorb the horizontal
As the construction does not need thrust of the arches. Neoprene pads
mortar, the blocks can be dismantled, placed in between the dry-assembled
and the bridge reassembled at different blocks avoid stress concentrations and
locations. If the construction is no longer control the friction properties of the
needed, the materials can simply be interfaces, echoing the use of lead sheets
separated and recycled. or soft mortar in historical masonry
construction.
Strength through geometry In plan, the boundaries of the structure
Striatus is an unreinforced concrete form deep arches that transfer horizontal
structure that achieves strength through loads (for example, from visitors leaning

18 Issue 247 • dw