Prefabrication experiments - 261 - Connectors - 02 - Abstracta building system

 

Transferring know-how from object, product or commodity production to large-scale building construction has motivated a spectrum of potential building systems both in theory and in practice. Volumetric modular stacking as an approach to industrialized building has been compared to modular toy assembly sets. Toys, from Lego blocks to Lincoln Logs and the infamous Erector Set, were cited as procedural models for simplifying onsite assembly. Modular kits composed of controlled, standardized and compatible parts, still fairly marginal in building, have been successfully applied in furniture assembly. Elements are categorized, bundled and packaged according to predetermined formal or functional objectives. 

 

Scaling the modular kit from furniture to building was at the core of Poul Cadovius’ Abstracta reticulated structural frame system. The Danish born inventor, designer and producer conceived the system in the late 1950s and filed for a patent in 1964. The Abstracta system is composed of a formed cast steel connector joint with a varying number of specially profiled appendages ending in a spherical bulge that fits and locks into tubular struts of varying lengths. The connectors are designed on the same principle as Cadovius’ modular furniture kit with one key difference: the size and thickness of the tubular struts have a minimum diameter of 45mm and a wall thickness of 3mm. The straight member spokes are manufactured with an internal globular pocket for the connector spigot, lodging it in place and resisting compression and tension. The same connector and struts can be assembled into 3d structural matrices to make exhibit structures, scaffolding or even large scale dome and freeform structures.

 

The Abstracta system was awarded the Gold medal in 1961 at the International Inventor’s Congress in Brussels. Its application in building remained negligible. Casting a connector with varying limbs both in terms of spigot angles and a specific shape demands production processes and tolerances that have not been the norm in building construction. Further, the design of hub connectors in general architectural systems has not tackled requirements to coordinate systems other than structure and it is difficult to imagine one connector capable of attaining such universality. Cadovius’ Abstracta system’s ongoing application in furniture still inspires the longstanding intention of assembling architecture with the simplicity of a toy. 

Patent drawing for the connector

Prefabrication experiments - 260 - Connectors - 01 - The Universal Building Joint

Architecture and construction in their basic essence are related to joining. Connecting, linking, aligning and fitting materials together require knowledge of both crafting and detailing. Joinery reveals how architecture is made. The modern architect streamlined design and construction through systematized thinking translated into translatable and intelligible building assemblies. Factory production made detailing into a language for the architect to showcase how to build through drawings and specifications. The search for the universal connector was an underlying theme of the modern architect’s new role of detailing construction.

 

The most cited and prominent example of this ideological vision of a multifunctional building joint leveraged toward multiple patterns is the General Panel House connector created by Walter Gropius and Konrad Wachsmann in 1941. The heart of the modular panel house system, the pluri-directional surface connector, was developed to join panel edges horizontally and vertically to arrange an infinite number of dimensionally coordinated variations. Inspired by his training as a cabinetmaker and as chief designer for the Christof and Unmack timber house producer, Wachsmann devised a steel biscuit joint precisely shaped and connected through a plate and wedge system. The plates were cut and shaped to match-up with the precision of a lock mechanism.  The hook-type metal clips would be kept in a latched and locked position by a compression steel plate wedge inserted through the panel’s thickness attaching panel and joint. Modular stressed skin panels and planning modules were outlined by what at the time had become the standard for material coordination: 4-inch module and 40-inch grid. The connectors were positioned according to the grid creating a repeated stitch pattern. 

 

The General Panel Corporation set up in a repurposed aircraft factory was to be highly automated and influenced by the era’s highest production standards. In 1984 Gilbert Herbert recounted the story of the General Panel Corporation in his book The Dream of the Factory Made House and cited many reasons for the company’s failure to attain what Wachsmann had promised. 

 

Architecture’s and architects’ fascination with joinery is still an obsession throughout the discipline and the quest for a universal connector is the theme of the next 10 blog posts which will present a number of connectors designed to attain a universally applicable joint.

The universal connector

Prefabrication experiments - 259 - Operation Breakthrough - 10 - Descon-Concordia's forward looking platform architecture

Design for manufacturing and assembly (DfMA) or the concept of product architecture, already applied in various industries, have been put forward as strategies for applying the same methodologies to building production. Kieran and Timberlake’s manifesto (Refabricating architecture, 2004) and an abundance of literature since the publication seem to point to modularization, design platforms, and offsite fabrication as outlets for lean production.  A recent example of this ideology explored by Bryden Wood, Platforms Bridging the Gap Between Construction and Manufacturing, develops similar notions including virtual modeling and prototyping and data harvesting to streamline the building process. 

 

Even as platforms are being identified as ground-breaking, theories for increasing productivity and product architectures are not new concepts. Perhaps terminology has evolved but the type of systemic breakdown of a project’s components and logistics were central to Operation Breakthrough. Proposals were truly innovative in this regard as many were based on comprehensive logistical frameworks similar to what has been recently titled a building platform approach to DfMA (pDfMA). 

 

One specific example and the only foreign project approved for US construction was the Descon-Concordia panel system. The sophisticated management plan included an open structural system of reinforced concrete factory-produced prestressed modular panels. From two storey to twenty-two storey high collective dwelling units, panels would be prepared in accordance to specific structural criteria while all other elements were to be shared between different designs and scales. Large reinforced concrete panels, off-the shelf components and mechanical sub-assemblies were part of the overall modular ideology shared between collaborating partners. This collective modular and dimensional coordination created an environment for manufacturers to produce all required elements concurrently for different sites, increasing production and productivity. Five modular panels for walls and four panels for ceilings made up the essential building blocks for a large number of designs. The proposer defined their system as a flexible management system and building kit : a type of product platform for reforming construction’s lagging challenges. Descon-Concordia, a consortium from Montréal, Canada was arguably the most advanced, forward-looking system in Operation Breakthrough and would certainly still be considered as a great innovation today in matters of applying factory production to building construction. 

Descon-Concordia building components and management system

Prefabrication experiments - 258 - Operation Breakthrough - 09 - Pemtom's three-dimensional housing matrix

 

Mat modular housing is a longstanding idealized experiment in planning spatial and geometric relationships for dwellings. The regulating grid unites housing dimensions, criteria and collective dynamics with standardized production parameters. A dwelling field, clusters expanded horizontally and vertically could be programmed for low, mid and high-density patterns. Further, the volumetric tessellation could be mapped over any topography and setting as each unit is a type of generic kernel.  

 

The Pemtom group’s proposal for Operation Breakthrough represents still another view of this highly peddled architectural experiment. Each factory-produced volume would be composed of walls, roofs, and floors, outlined by a rigorous grid module, 13’ (3.9meters) x 13’ (3.9meters) x 9’ (2.7 meters) and constructed from stressed-skin panels. The structural insulated panels (SIPs) of stressed skin construction employed the same composite structure, a laminate of plywood layers and an insulating urethane core, as the panels that had been previously been studied by the US Forest Service as far back as 1937. Pemtom’s proposal references USFS research.

 

Nine juxtaposed, stacked and aligned building blocks would be required to organize a 1500 square-foot three-bedroom dwelling. Each volume was programmed for particular dwelling functions, rooms and living spaces, while more mechanically complex designs could be used for bathrooms, kitchens or service cores. 12 spatial units were provided in the proposal as a catalogue of composing parts.  The sections attached to one another formed a uniform structure with a few composing parts. The clustered volumes or boxes would be mass-produced and their on-site juxtaposition streamlined up to fifteen stories high within a concrete or steel cradle or mega-structure. As described and illustrated, the three-dimensional grid regulates of every part of the building system without any evident hierarchy or separation of the public, private or common areas.

 

Pushed in many forms, this type of normalized housing has been largely opposed by market forces perhaps because architects and manufactures never provided for the conceptual interfaces between architecture, production and individual habitability. Pemtom’s proposal foreshadowed current information based experiments and DfMA approaches where building platforms are delineated by and limited to a controllable quantity of customizable options in a scalable housing system.

Pemtom's catalogue of parts

Prefabrication experiments - 257 - Operation Breakthrough - 08 - Birdair and Poly Petro Chem - inflatable forms

The most noteworthy aspect of Operation Breakthrough is the amount of partnerships formed to respond to the challenges of construction’s lacking productivity and reinvent industrialized building. This reinforced George Romney’s affection for cooperative capitalism and cross-pollinating stakeholders. The result, leveraging the construction industry and its composing partners toward an open source sharing of strategies - a catalogue of construction techniques - could be an example to today’s still lagging construction industry. Expressly within the framework of identifying affordable housing systems, Operation Breakthrough provided a space and platform for presenting well-known as well as more marginal systems, materials and methods. A prime example of an inventive industrial partnership was provided by the consortium identified as Housing Advocates composed of Birdair (a tensile structure producer) and Poly Petro chem (a plastic producer). Both companies came together to imagine a building system and process articulated to their specific areas of expertise. 

 

Birdair is well known for their tensile structures.  The company’s foray into inflatable and reusable concrete formwork leading to the publication of a patent (US723751A) was the main element of their proposal. The idea is to employ Birdair’s knowledge of inflatable tensile structures to produce an inflatable, fill it with enough pressured air to shape a compressive geometry and its structural formwork. Fluid material could then be poured or cast onto the inflatable and left to set and cure. Once cured the reusable formwork could be deflated, removed and set-up to cast other structures. For Operation Breakthrough, the on-site concrete was replaced by a material identified as Carbalon; a two-part urethane compound sprayed, or cast onto any mold. This material would be hardened over Birdair’s reusable and inflated forms to shape exterior walls, and interior walls, while service cores and other required components would be produced by third party partnering manufacturers. 

 

The inflatable forms would be anchored in place by strapping the tensile structure over a foundation. Door and window openings, part of the casting mold, would also be positioned in place while casting the material and allowing it to cure into a monolithic structure, which could then be finished in a variety of ways from traditional siding to stuccoing. Along with the casting controlled on-site with portable equipment, the pneumatic formwork creates a site intensive industrialized construction process. 

Sketch of the Housing Advocates proposal