Prefabrication experiments - 454 - Digital paradigm shift

 

Digital design and construction have initiated a new paradigm in building production. While edifices remain prototypes, generally built only once, making them in a virtual environment before assembling them onsite, makes it possible to identify and eliminate costly coordination and systemic entanglement errors that would habitually be addressed on site. This type of digital twin approach facilitates prefabrication and potentially transforms conventional building processes by placing all stakeholders, including manufacturers in the planning stages of a project. A significant shift from the design-bid-build model toward an integrated collaborative and streamlined process from design to fabrication and to assembly, virtual coordination is also seen as a driver for increasing factory production in architecture as it lines up with DfMA and Lean management principles. 

 

Lessons learned from past paradigm swings in construction have often touted the promise of prefab but offsite construction’s share of construction remains marginal. Today, proponents are demonstrating the inflection of a personalized design and fabrication process which include manufacturing parameters from design genesis. Subassemblies for floors, walls, mechanical systems, and other building requirements can be produced as parts or as complete large-scale chunks to be packaged, sequenced and delivered for assembly onsite. Contingent to greater preparation, precise models and a deeper knowledge of supply chains, lead times, manufacturing challenges, reduces waste at every step.  Working together on a virtual model stakeholders can relate to issues from design to construction management in real time, agreeing to any reworkings before anything gets put together. 

 

Digital twins introduce a novel way of looking at prefabrication which is very different from industrialized construction of the past as each project remains a prototype using factory production to make things better, in a controlled setting and on time without the seriality of mass production. While many feel that this type of virtual construction will lead to greater offsite uptake for the construction industry, it does not address the fragmented industry and will not necessarily lead to lowering costs. Perhaps this new take on custom prefabrication will, however, make it a far less scary word for sensitive architects worried about affirming their creativity. 

 

Bryden Wood's digitally informed façade kits

Prefabrication experiments - 453 - Prefabricated Aluminum Shell Houses (1951)

 

Achieving a maximum form/space relation with minimal resources was a fundamental topic in modern dwelling design along with its potential industrialization. Vaulted Quonset huts, panelized A-frames, shotcrete sprayed domes, all symbolize the quest for an optimal tuning of materials with shapes to assemble walls and roofs, seamlessly. Vaults, shells and simple triangular trusses can be built with any material but mass production and later the military industrial complex underwrote innovative use of plastics, plywood, steel and aluminum. All progressed during the first half of the 20th century and paralleled architectural modernism's aim of maximum affordability. Using resistant geometries to create coverings coveted by many modern architects required materials with the capacity to be shaped while maintaining their strength and durability. 

 

Aluminum perhaps above all represented the newness and lightness associated with aviation. Combined with simple aerodynamic forms, its possibilities inspired a construction system, designed my modern master Jean Prouvé : a small scale airplane wing deployed as a curved shed roof. Outlined through industrial collaboration with aluminum manufacturers in France, Prouvé presented the «shell houses» or the Maisons Coques at the 1951 Salon des arts Ménagers, an exhibit showcasing advances in domestic functions, trades and crafts. The small houses were made from stressed skin aluminum elements curved to create a type of awning component supported on either end by similar vertical stressed skin bearing walls. 

 

Employing the architect's usual 1-meter grid, the panels, composed in a linear arrangement, for walls and roofs could simply be juxtaposed, assembled and later disassembled. The process could be industrialized using the same technology Prouvé had deployed with architect Bernard Zehrfuss for a shed saw-tooth roof structure for The Mame Printers at Tours. The solar and light reflection potential of aluminum stressed skin surfaces was valued for both exterior and interior applications. Vertical louvres used as shades positioned on the sun-facing wall conceived as moveable wings also provided an example of  Prouvé’s talent for shaping lightweight metals, into industrializable components. This same system was used for building schools as it was basically just a wide spanning shell for any architectural space. 

 

Shell Houses in front of exhibit venue photo  https://strabic.fr/Jean-Prouve

 

Prefabrication experiments - 452 - Vaulted concrete innovations

Modern materials and methods revolutionized building construction. Reinforced concrete specifically evolved though many varied experiments during the 19th century into a material associated with multi-unit residential typologies as the artificial stone is composed of widely available resources, it’s also solid, durable, affordable, and fireproof. These characteristics make it the most used man-made substance on earth. Its important advantages are somewhat offset by a high weight to span ratio. With an approximate mass of 2400 kg/m3, concrete slabs, beams, columns, and other components contribute to structure’s significant dead weight. 

 

Inspired by Gothic vault stone fan or rib spanning systems, Vaulted AG’s cambered concrete floors employ similar geometric lines of force to reduce material use and capitalize on concrete’s compressive strength. While this type of ribbing used in waffle slabs or onsite produced void slabs is a first step to weight reduction, vaulted slabs exploit curved geometries to further increase structural efficiencies. Vaulted AG makes it possible to assemble efficient floor systems from industrialized parts that are bolted together to facilitate their assembly and disassembly. The arched voussoir-like fragments support lightweight floating mechanical floor plates shaping an open void network for distribution ducts, piping and other systems.  The vault’s extrados surface is hidden within the floor composition, while the intrados creates a beautiful gothic-like ribbed arched ceiling. Vaulted AG is a spinoff from research undertaken at the Block Research Group of ETH Zurich by professors Dr. Philippe Block and Dr. Tom Van Mele. Their prototypes were first exposed at the Venice biennale in 2016. 

 

A typical prototype square floor grid is assembled using 4 irregular pentagonal fragments supported by corner columns. An 8-sided central square concrete compression component locks all elements into place akin to an arch's keystone. Each pentagon’s ribs radiate from a thick intersection at the column junction and angled toward the central keystone exploiting a symmetrical arrangement. Perimeter tension members resist horizontal loads. According to inventors, optimizing compressive forces makes it possible to employ 80% less steel and 70% less concrete in a floor composition 65% lighter than a conventional one. Responding to the basic structural idiom of maximum span with minimal materials Vaulted AG revives historic building strategies to further modernize concrete construction.  

Floor system prototype

 

 

Prefabrication experiments - 451 - Micro-units designed for adaptive reuse

 

Adapting vacant, underused, neglected commercial buildings to respond to the affordable housing crisis can potentially be to today’s procurement challenges what the mobile home and cheap prefabs were to interwar and postwar 20th century housing production. Intensifying use of deserted central neighborhoods also leads to less sprawl revaluing derelict spaces. Many have suggested that adapting existing buildings to new functions is complex and costly, even arguing that new construction is cheaper. Considering its complicated logistics redeploying existing infrastructure offers environmental benefits by reducing, reusing and recycling components and materials.

 

Implanting systems for private kitchens and baths can certainly be expensive and structurally complex as most commercial building floor plates were not designed to service multiple flat layouts. Imaginative co-living patterns provide opportunities for sharing services; appartements can offer autonomous private spaces with wet core services placed to be shared among many occupants, reducing mechanical distributions. This type of micro-unit community was projected by London firm SHED. The tiny units can easily be slipped into any building. The no frills living standards offer a safe and private place to live, sleep and work. They also help revive buildings that otherwise would slip further into disrepair. 

 

Tim Lowe, an architect from Studio Bark, the founder of the SHED project sees their approach as a win-win low rent strategy. Conceptually, the integrated furniture units are a type of Ikea kit framed within a streamlined supply chain; The modular volumes’ components can be produced serially to efficiently distribute low-cost micro-dwellings.  All elements including wall panels are designed to be assembled or even disassembled using a mallet and a screwdriver in a day. Insulated for acoustic and thermal comfort, interiors would include a small space for working along with a closed area for sleeping. All other dwelling requirements are shared.

 

In a typical central core office layout, the central core could be adapted to include common kitchen and baths using the existing vertical ducts with the living pods being distributed freely on the open floor plate. While admittedly not a total solution to solve housing shortages reusing existing infrastructure does substantially diminish massive material extraction required by new edifices.  

Moveable unit in an existing building