Bracing Holds Promise of Collapse-proof Buildings in Quakes

Across the world, more than two billion people live in earthquake danger zones. Researchers at the Fraunhofer Institute for Wood Research WKI are working with industry partners to develop building materials designed to prevent building collapse in a natural disaster.

Engineers are working on ultra-durable bracing that will protect even high-rise buildings during an earthquake.

Sensor-controlled bracing connectors can protect a building’s structural integrity. Credit: Fraunhofer Institute for Wood Research WKIThe bracing consists of sensor-controlled steel connectors. These are intended to provide a high level of rigidity while remaining elastic enough to maintain structural integrity in the face of severe shaking.

In one test, the researchers investigated the nature of the stress being placed on structures by applying static, cyclical and dynamic forces; in another, the structure's service life was tested using environmental simulation. The tests show the bracing works as intended, researchers say.

The earthquake-resistant bracing is intended for buildings with a mullion-and-transom design, and connects the horizontal beams with the vertical post. When exposed to wind or tremors, the connectors must be rigid enough to keep deformation to a minimum, but also elastic enough to withstand strong earthquakes. If deformation does occur, it does not lead to critical stress; in other words, the building sways, but does not collapse.

Researchers says that in an earthquake, the connectors slide over each other, converting kinetic energy into frictional energy and preventing the building from collapsing.

Norbert Rüther, project manager at Fraunhofer WKI, says: "The trick is using friction to dissipate the force. The individual parts of the connector are pressed against one another applying a significant, pre-defined force. When the specified stress limit is exceeded, they begin to slide over each other."

As a result, structural deformation is accommodated without compromising structural integrity. Even after a strong earthquake, the structure maintains the same capacity as before, and is still able to cope with the stress placed on a multistory building. Researchers say that buildings can withstand several quakes without suffering significant damage.

Researchers also developed pressure and temperature sensors integrated into the connector, which means it is possible to measure the forces and stress associated with an earthquake.

The connectors are currently in the prototype stage, and are expected to be ready for full-scale production in one to two years. Work is under way to explore the connectors' economic viability with a view to testing in real buildings.