Most Spanish buildings constructed before 2000 are vulnerable to progressive collapse in the event of structural damage, as the most stringent engineering standards have been adopted this century. As climate change and geopolitical tensions introduce new uncertainties, the need for robust construction is growing.

"Today's buildings can withstand localised and unforeseen failures without suffering disproportionate or progressive collapse, thanks to the use of sufficient structural continuity to redistribute loads beyond the damaged element. These standards were not widely adopted until around the year 2000, following events such as the collapse of Ronan Point in the United Kingdom and the attack on the Alfred Murrah Federal Building in the United States, and only the most advanced regulations have implemented them to date", explains Manuel Buitrago, a researcher from the Building Resilient group at the Universitat Politècnica de València (UPV), which has developed the innovation.

In older buildings, these deficiencies can be rectified. However, traditional reinforcement techniques have drawbacks. "They tend to focus on providing greater strength to individual components, such as beams, floor slabs or columns. However, this component-level approach causes significant disruption to the building's normal operation and proves very costly when dealing with widespread deficiencies," points out Jose Adam, a researcher in the same group.

The research team at the Universitat Politècnica de València (UPV), Building Resilient, part of the ICITECH Institute, has developed an alternative approach to global reinforcement that, in essence, consists of 'suspending' the building from the roof. "By installing highly rigid beams at the top of the structure, structural collapse is prevented. If any lower component fails, the structure remains suspended from these rigid roof beams, which redistribute the load to other areas of the building," adds Buitrago.

After validating this mechanism through high-fidelity computer simulations to optimise beam configuration, the team is conducting full-scale tests on a building constructed specifically for this purpose. "It is a reinforced concrete building cast in situ, constructed without taking modern robustness requirements into account, which is representative of the majority of existing older buildings in Europe," confirms Juan Sebastián Fontalvo, who is involved in research in the group.

The experimental validation process is divided into two distinct phases: during the first phase, reinforcement was installed in the roof, consisting of steel beams connected to the building's concrete beams and columns, and a load was applied to the floor slabs. Subsequently, an extreme event was simulated by completely removing a critical column on the ground floor. The structure remained stable and sustained only minor damage, thanks to the load redistribution provided by the roof beams. Following this phase, a thorough repair was made to restore the structure to its original condition.

During the second phase, completed today, 20 July, the roof reinforcement beams were removed, and the same column removal scenario was repeated on the unreinforced structure. As anticipated, the building underwent a complete progressive collapse. Thanks to these experiments, empirical verification has been obtained that the proposed reinforcement is a viable strategy for protecting existing infrastructure with vulnerabilities.

The research project, known as ENHANCE, is being conducted with funding from the Valencian Regional Government through the Prometeo grant awarded to the Building Resilient group.