Demountable connections and circular construction

The review examines demountable connections across steel, concrete, timber, masonry and hybrid systems, relating component reuse to strength, stiffness, ductility and performance after reassembly. It considers both end-of-life recovery and replacement during use.

The authors identify promising connection systems, but limited long-term practical evidence and unresolved questions about residual capacity and reassessment. Demountability alone does not establish that a recovered component is fit for reuse.

ExoSett’s accommodation modules are intended to be installed, removed, replaced or relocated while the supporting frame remains in service. For these interfaces, controlled disassembly is part of normal building operation. Keeping the frame in service does not imply uninterrupted occupation nearby: local isolation, temporary restraint and controlled access may still be needed.

The frame itself need not be committed to one building for its entire useful life. In event accommodation or other temporary installations, an accommodation frame could eventually be dismantled and its beams, columns, frame-node assemblies and other components assessed for reuse elsewhere. Demountability therefore extends to the primary load-bearing structure.

Some frame designs may also permit individual beams, columns or frame-node assemblies to be replaced during a building’s working life. This would require a carefully engineered procedure: surrounding modules might first be removed and the relevant loads temporarily transferred or relieved through jacks, temporary supports or other temporary works before removing the component. These are design possibilities requiring engineering development, not established procedures applicable to every frame. A load-bearing role need not make a component permanently irreplaceable.

A connection that can be cut apart or dismantled once does not necessarily support controlled, repeatable disassembly. For both module interfaces and demountable frame joints, the design needs to establish access, removal sequences, load paths during intervention and performance after reassembly.

ExoSett already describes a frame node as potentially an assembly. Bolts, plates, shoes, engagement features and local reinforcement may work together as a structural junction. Their collective function matters; the node need not be a single component, nor need every module restraint be concentrated there.

For repeatedly operated interfaces, inspection, maintenance and replacement need to be designed in. Replaceable wear items or sacrificial components may be preferable to accumulating wear in the primary frame, provided their condition and replacement can be managed without compromising the load path.

Different phases may also justify different interfaces. Fittings for transport and installation need not provide the module’s long-term restraint in the building. Separating these functions is an ExoSett option to investigate, not a solution established by this paper.

• Repeated use and wear: Which module/frame connections will be operated repeatedly? Which parts should be replaceable wear items, and how will tolerances be maintained after successive installation cycles?
• Frame replacement and reuse: Which beams, columns and frame-node assemblies should be replaceable during a building’s life, and what temporary load-transfer arrangements would make that safe? How should dismantled frame components be assessed for reuse elsewhere?
• Inspection and protection: How will connections be inspected once a module is occupied? How will corrosion and fire protection remain compatible with access and demountability?
• Division of functions: Should conventional transport corner castings remain on installed modules, or should transport fittings and in-building attachment be separated? How much restraint belongs at the frame node, and how much can be distributed around the accommodation frame?

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