Tensioned stone
It has also been used in more unusual stonemasonry applications: arch stabilization, foot bridges, granite flag posts, cantilevered sculptures, a space frame, and staircases.
It is also aligned with mass timber and straw structural insulated panels (SSIPs), which are all reconfigurations of traditional materials for modern construction that involve some pre-fabrication.
[5] The tensioning process imparts a compressive force to the stone, which improves its capacity to resist tensile stresses that could otherwise cause cracking or failure.
[8] In pre-tensioned stone, the tendon (a steel rod) is held in tension with jacks while the remaining cavity in the duct is filled with epoxy grout.
Walls, columns, beams and slabs could all be made from small pieces of factory-sawn stone, cut and pre-drilled to a design of standard components.
In the mid-20th century, the Sydney Opera House shells were constructed from pre-cast concrete masonry beams that were assembled into a pointed-arch vault using post-tensioning.
"[17] As retrofitted seismic bolts were previously used, it appears likely that the GPO's priority claim relates to how the structural calculations guided the tendon placement and increased tension forces.
"[21]The first documented real-world use of post-tensioned stone in a new building was for the Pavilion of the Future,[27] built in Seville for the Universal Exposition in 1992, designed by structural engineers Peter Rice and Tristram Carfrae of Ove Arup and Partners.
Completed in 1995,[30] Queen's Building at Emmanuel College, Cambridge[11] by Hopkins Architects and Buro Happold[7] with Ove Arup and Partners.
"[32] Completed in 1999, Punt da Suransuns[33] in Switzerland, is a 40 m footbridge[34] designed by civil engineers Jürg Conzett and Gianfranco Bronzini.
"[35]Erected in 1999, Southwark Gateway Needle by Eric Parry is made of 25 blocks of Portland stone held 16m high by post-tensioning.
Starting in 2011, award-winning high-tensile stone staircases for luxury residences were constructed through a collaboration between stonemason Pierre Bidaud and structural engineer Steve Webb,[44][25][45] In 2013, Giuseppe Fallacara and Marco Stigliano demonstrated a "tensegrilithic" prototype, combining stone with steel rods and cables into a tensegrity structure.
[50] In 2020, IABSE awarded the Milne Medal to Steve Webb for his innovations using low-carbon materials in structural engineering, including wood and tensioned stone.
[51] In 2022, Jürg Conzett and Gianfranco Bronzini were awarded the Swiss Grand Award for Art (Architecture) to recognize their body of work, which includes a number of tensioned-stone footbridges, including Punt da Suransuns (1999), the Waterfall bridge along the Trutg dil Flem[52] trail, and Orrido di Cavaglia[53] (2021).
[55] In 2024, the Royal Academy of Arts summer exhibition displayed a stone–steel space frame (3D truss) made from cored, tensioned cylinders of limestone and steel joints.
"Imagine crane masts, bridges or space frames like the Eden Centre and Stadium Australia being formed with stone elements instead of steel.
With a world-saving 75 per cent carbon reduction, inherent durability and fire resistance, we can put waste stone to use and make some really pretty structures."
—Steve Webb[56]Due for completion in 2026, the Sagrada Familia cathedral under construction in Barcelona in partnership with the Arup Group uses post-tensioned stone assemblies.
[19] "Jordi Faulí, the architect in charge of La Sagrada Familia in Barcelona, has stated that they will implement this technique for 800 panels that form part of the central towers of the basilica; in fact, prestressing will allow for a higher resistance to winds with less weight."
