Jun 30, 2011 13:42 GMT  ·  By
Sensor skin could be wrapped around troublesome areas on a building, and monitor every change once every 24 hours
   Sensor skin could be wrapped around troublesome areas on a building, and monitor every change once every 24 hours

Engineers at the Massachusetts Institute of Technology (MIT), in collaboration with German physicists at the University of Potsdam, develop a coating material that can be used to monitor building integrity.

The team says that the sensor-laden, fabric-like material has electrical properties, and that it could be inexpensively adhered to structures were structural failures are likely to occur. The underside of bridges or the walls of old buildings are just some of these potential locations.

Using this system, engineers could find out when cracks develop in concrete, for example, and start mitigating the situation before things get out of hand. This approach would replace standard visual inspections, which are currently the norm.

Surveying a building visually alone is too slow and expensive. The procedure is cumbersome and often dangerous, and is part of the reason why the American Society of Civil Engineers (ASCE) assigned the grade “D” to the overall quality of infrastructure in the United States back in 2009.

The new material was developed with federal stimulus funding, and is aimed at helping critical and non-critical infrastructure in the country improve their grades. The field of high-tech, affordable, continuous monitoring of structures is currently still in its infancy.

With the new flexible skin-like fabric, a huge stride has been taken in this field, experts say. The work is detailed in the December 2010 issue of the journal Structural Control Health Monitoring, as well as in the April 2011 issue of the Journal of Materials Chemistry.

There are no prefabricated sheets of the new material. Rather, engineers and maintenance crews would simply order the length and width they desire for the structures they are monitoring. Installation is basic, given that all that's needed to set the system in place is glue.

Experts also developer two separate types of monitoring skin, one that is best used for detecting cracks caused by shear, the movement in different directions of stacked layers, and another that can more easily identify horizontal beam sags.

Each crack or distortion would change the capacitance of one or more patches in the fabric. A computer would analyze this capacitance every single day, and would detect with of the patches is changed.

The main benefit this system has is that it would detect changes as soon as they occur, regardless of size, and that it would also pinpoint the exact source of the changes.

“The sensing skin has the remarkable advantage of being able to both sense a change in the general performance of the structure and also know the damage location at a pre-defined level of precision,” explains Simon Laflamme PhD.

He conducted this research as a graduate student in the MIT Department of Civil and Environmental Engineering (CEE). Other team members included MIT CEE professor Jerome Connor and University of Potsdam researcher Guggi Kofod and graduate student Matthias Kollosche.

“Such automation in the health monitoring process could result in great cost savings and more sustainable infrastructures, as their lifespan would be significantly increased as a result of timely repairs and reduced number of inspections,” Laflamme concluded.