In the early hours of 16 May 1968, a gas explosion on the eighteenth floor of Ronan Point, a tower block in Newham, east London, triggered a partial collapse of the building’s south-east corner. The explosion itself killed one person. The collapse killed four more. What investigators found when they examined the structure was something that has troubled structural engineers ever since: the blast had not destroyed the building. It had removed a single panel, and the floors above had done the rest.
That kind of chain reaction, where local damage cascades through a structure far beyond the original insult, is called progressive collapse. A new study published in Nature Communications on 15 June 2026 proposes a specific engineering solution. Force-regulating fuses build collapse risk into a managed sequence: rather than letting damage cascade, these mechanical devices embedded in reinforced concrete break structural continuity at a defined force threshold, just as an electrical fuse breaks a circuit before a fault spreads. These mechanical equivalents break structural continuity before a local failure becomes catastrophic.
The research introduces both the device concept and a low-cost laboratory test method for simulating building collapse propagation without constructing full-scale structures. Both contributions matter. Force-regulating fuses for building collapse prevention address a problem that existing engineering codes handle unevenly, and the test method means the concept can be evaluated far more quickly and cheaply than before.
Structural continuity is, in normal circumstances, a good thing. When a floor slab is connected to beams, and beams are connected to columns, and columns are tied to the foundations, the entire building acts as a single integrated system. Loads are shared and redistributed. A single overloaded beam can transfer some of its load to its neighbours. The structure is more robust than the sum of its parts.
The problem arises when the initial damage is large enough to overwhelm the structure’s redistribution capacity. Remove a column from a reinforced concrete frame, and the beams above try to carry the load as a catenary, hanging in tension rather than bending. If the connections can handle that transition, the structure survives. If they cannot, the slab above the missing column drops onto the slab below, doubling the load on that level. That slab then drops onto the one below. The collapse runs downward through the building like a controlled demolition that nobody triggered on purpose.
Force-regulating fuses interrupt this sequence. Placed at specific points in the structure, they are designed to yield, deform plastically, and absorb energy when forces exceed a defined threshold. In doing so, they break the structural continuity that would otherwise transmit collapse forces from one part of the building to another. The damaged section is isolated. The rest of the structure remains intact.
Under normal loading conditions, the fuses contribute to the building’s stiffness and strength like any other structural element. They are not weak points. They only behave differently when extreme, abnormal forces arrive, which is exactly when you want a different behaviour.
One of the more practical aspects of the research is the retrofit potential. The concept of force-regulating fuses building-collapse protection into existing frames, rather than requiring demolition and rebuilding, is central to the paper’s argument. The devices are described as suitable for both new construction and retrofitting into existing structures. This matters because most of the building stock that needs to be more resilient has already been built. Designing better new buildings is worthwhile. Improving the millions of existing reinforced concrete frames is a different and larger challenge.
The retrofit potential depends on how the fuses are integrated. If they can be installed at beam-column joints or slab connections without extensive demolition, the economics of upgrading existing structures become more feasible. The paper’s low-cost laboratory test method is relevant here too: it allows engineers to assess an existing structure’s vulnerability to progressive collapse without a full-scale test and to evaluate whether a retrofit improves resistance before committing to the work.
Understanding force-regulating fuses and building collapse scenarios extends well beyond explosions. Vehicle impacts on columns, extreme flooding that undermines foundations, and even severe construction errors have caused similar cascading failures. Any building whose columns could be compromised by foreseeable events could potentially benefit from this approach.
Engineering Deep Dive: Progressive Collapse, Structural Mechanics, and the Design of Force-Regulating Fuses
To understand how force-regulating fuses work, it is useful to start with the mechanics of a reinforced concrete frame under normal and abnormal loading. In normal use, a floor slab distributes its load to beams, which transfer it to columns, which carry it to the ground. The loads are primarily compressive in the columns and involve bending in the beams and slabs. Engineers design for these loads using well-understood methods derived from the theory of structures, combining material properties such as the compressive strength of concrete and the tensile strength of steel reinforcement with geometric factors such as the span and depth of members.
When a column is suddenly removed, whether by explosion, impact, or corrosion failure, the load it was carrying does not disappear. The structure must find another path to the ground. In a well-designed frame, the beams spanning over the missing column attempt to act as a catenary, a hanging chain carrying load in pure tension rather than bending. This is sometimes referred to as the tensile membrane action of the floor. For this to work, the connections between beams and columns must be able to carry tension, not just the shear and bending they were originally designed for, and the beams themselves must be ductile enough to deform without fracturing.
Many older reinforced concrete buildings were not designed with catenary action in mind. Their connections are brittle rather than ductile, or the reinforcement detailing does not provide the continuity required. In these cases, the alternative load path does not develop and the slab above the missing column drops. Impact loading on the slab below can exceed its dynamic load capacity. If it fails too, the cascade has started.
Dynamics complicate the mechanics of progressive collapse. When a floor drops, it does not settle gently onto the one below. It falls under gravity and arrives with velocity. The kinetic energy at impact can be many times the static load the lower slab was designed to carry. This is a familiar concept from A-level Physics: kinetic energy is proportional to velocity squared, so even a fall of half a metre can deliver an impact force far exceeding the static weight of the dropped floor. Engineers quantify this using dynamic amplification factors, which account for the fact that a rapidly applied load is more damaging than the same load applied slowly.
Force-regulating fuses are designed to interrupt this process by controlling the force transmitted between structural elements. The fuse element is engineered to yield at a specific force level, absorbing energy through plastic deformation rather than transmitting peak forces to adjacent members. This is analogous to a crumple zone in a car: the crumple zone does not make the car stronger; it makes the car better at absorbing and dissipating energy so that the occupants experience lower peak deceleration forces.
The yield threshold of a force-regulating fuse must be chosen carefully. Too low, and the fuse will activate under normal service loads, which is both dangerous and a nuisance. Too high, and it will not activate quickly enough during a collapse event to interrupt the cascade. The threshold must sit above the maximum force the fuse will experience under normal and extreme-but-survivable loading, but below the force level at which uncontrolled propagation would begin.
The low-cost test method described in the paper is important because testing collapse propagation at full scale is extraordinarily expensive and logistically difficult. You cannot drop one floor of a real building onto another to see what happens. The new laboratory method uses scaled specimens, careful instrumentation, and controlled loading to replicate the key mechanical features of a propagating collapse at a fraction of the cost of a full-scale test. This allows many more design variations to be evaluated, which in turn allows the fuse geometry and yield threshold to be optimised much more efficiently.
For A-level students studying Physics, the concepts involved span several topics. Moments and torques govern how loads are distributed in beams. Material properties, including yield stress, ductility, and energy absorption, are central to understanding why some structures survive while others do not. The dynamics of impact, including the conservation of momentum and energy, explain why the propagation of collapse is so destructive. And the principle of the fuse, whether electrical or mechanical, is a clean example of using a controlled weak point to protect a more valuable system.
The idea of a mechanical fuse for buildings is, on reflection, almost obvious. Electrical engineers have used sacrificial components to protect circuits since the 1880s. Automotive engineers build crumple zones into cars. Aerospace engineers design frangible bolts that release controlled separations. Structural engineering has largely relied on strength and ductility alone. The concept of force-regulating fuses building-collapse resilience into a structure; it does not replace strength or ductility. They add a layer of protection specifically for scenarios where strength and ductility alone are not enough. For students drawn to civil or structural engineering, the Ronan Point collapse still offers a lesson worth learning: buildings fail in sequences, and understanding the sequence is the first step to interrupting it.
- Engineers have developed force-regulating fuses that can be embedded in reinforced concrete buildings to prevent progressive collapse
- The fuses work like electrical fuses, selectively breaking structural continuity when forces exceed a safe threshold
- A new low-cost laboratory test method allows researchers to simulate collapse propagation without building full-scale structures
- The approach could improve the safety of both new builds and existing structures through retrofit
