Steel modular connections: lessons for removable accommodation

The paper compares nine research-stage steel module-to-module connection systems, with the commercially deployed VectorBloc system providing a separate reference point. Approaches include locating pins, plug-in connections, brackets, post-tensioned rods and systems intended to dissipate earthquake energy or return towards their original position after loading.

The review considers structural performance alongside assembly, cost, sustainability and reuse. No system performs best in every respect. The authors identify substantial gaps in fire-performance evidence, long-term durability and practical disassembly and reuse testing.

The paper provides a useful introduction to connection concepts and their trade-offs. Its comparative scores and reuse estimates should be treated as indicative; selection for a particular application requires examination of the underlying studies and verification of the proposed detail.

Shipping-container technology remains a reasonable working and reference model for ExoSett. Corner castings, twist locks and the wider range of container connection accessories demonstrate how a standardised interface can support different devices for lifting, transport, positioning and restraint.

ExoSett has never depended on using shipping-container hardware specifically. The patent deliberately leaves room for different implementations. The Design section follows the same approach: the Frame designer and Module designer must agree a compatible interface and establish its performance, rather than adopt one prescribed proprietary connector.

This paper provides an initial view of a wider range of technically credible approaches beyond familiar container-derived methods. It reinforces that position: compatibility and required behaviour should be defined consistently, while allowing different connection designs to satisfy them.

The structural distinction remains important. The paper principally concerns connections between modules that participate in the building’s structural system. ExoSett requires connections between accommodation modules and a supporting accommodation frame. The reviewed systems cannot be assumed suitable for that different role without engineering development and verification.

• Alignment and positioning: Distinguish features that guide a module into place from those that provide its final restraint, and make correct engagement verifiable.
• Restraint and load transfer: Define the forces and movements the interface must accommodate during installation, occupation and removal, with clear load paths at each stage.
• Tolerance management: Allow for manufacturing and erection variation, frame movement and wear over successive exchanges without compromising fit or restraint.
• Disassembly and reuse: Fast engagement does not necessarily mean easy release. Provide controlled removal after a period under load, access for tools and inspection, and acceptance criteria before reuse.
• Replaceable components: Investigate both replaceable wear parts for repeated module exchange and, where justified, sacrificial elements that protect the main module and frame during exceptional loading. These serve different purposes and require defined inspection and replacement procedures.
• Durability, inspection and fire: Address corrosion, loosening, wear and inspection access together with fire protection and connection behaviour at elevated temperatures.

These are ExoSett design questions informed by the review, not solutions validated for ExoSett by its authors.

Read the related discussion of demountable connections and circular construction, or return to Research and Reading.