Concrete is used everywhere and particularly in critical areas such as high-rise buildings, bridges and industrial facilities. As a construction material concrete offers strength and versatility and its production materials gravel, sand, cement, water and steel rods - are readily available. But the strength of concrete, particularly the foundation piles, can be damaged during or after installation or indeed over time if subjected to unforeseen stress.
Under the European Union (EU)-funded Pile-mon project, a consortium led by the Northern Ireland company Bullivant Taranto Ltd has developed an innovative monitoring system which can test the integrity of newly made pre-cast concrete foundation piles and monitor performance over their lifetime.
The Pile-mon approach involves embedding special electrical circuits or 'wire tags' in the concrete pile during manufacturing. A remote monitoring device can subsequently be attached to the pile and electronically signal any changes in critical areas due to cracks or stress.
"The foundations of most buildings and bridges on poor ground are made from pre-cast concrete piles which are hammered into the ground as a series of segments. With our inbuilt sensing technology at the top and bottom of each segment, we can check the internal integrity at any moment," says project leader Simon Bullivant.
The Pile-mon consortium, composed of engineering and research organisations in Ireland, Germany, France, Spain, Iceland and the UK, set out in 2008 to develop an innovative quality assurance system which could provide a cost-effective and reliable means of monitoring the integrity of pre-cast concrete piles throughout the supply chain from manufacturing right through to installation and beyond.
The consortium has developed low cost wire tags which can be embedded in the concrete sections where they provide data on the history of the pile (batch number, periodic integrity checks, etc) and help verify if a segmented pile composed of several concrete sections has been successfully driven into the ground and will support the design load.
"The key focus of this technology is detecting potential cracks in buildings, bridges and other critical infrastructures even nuclear facilities - via these embedded wires," Bullivant explains. "The technology is also very useful to test concrete piles which are being re-used on other projects to ensure they are safe", adds the project leader.
According to Bullivant, other traditional approaches such as ultrasonic testing exist, but have limitations. "The Pile-mon sensing technology is cost-effective and can be used on segmental concrete piles deep underground. The energy source for monitoring is provided by the external inspection device," he adds.
The European Commission identified possible synergy of the Pile-mon technology with another EU-funded project, 'Performance of Innovative Mechanical Connections in Precast Building Structures Under Seismic Conditions' (SAFECAST), which focused on safe concrete construction in earthquake zones, and put the two groups in contact.
The SAFECAST project brings together pre-cast concrete manufacturers and building research bodies in Italy, Turkey, Portugal, Greece, Germany and Slovenia. They have jointly developed common design procedures to improve the seismic resistance of pre-cast concrete buildings in vulnerable areas.
SAFECAST has been working with the Pile-mon team on the application of the 'wire tags' technology to these critical concrete joining sections. This is expected to permit the integrity of the sections to be checked at any time and particularly after seismic activity.
The potential benefits of this are great in terms of time-saving and the efficient use of resources. Following a tremor or serious seismic activity, engineers will be able to remotely check the safety of the joining sections of Pile-mon equipped buildings and make quick decisions about building safety. The new design standards developed by SAFECASTcombined with the Pile-mon inspection system are expected to bring enhanced building safety in seismic zones.
The Pile-mon technology is now being taken to the production stage and partners are being sought to make it available worldwide. The SAFECAST project was completed in February 2012 and the recommended design procedures are expected to improve the standards for construction in seismically threatened areas of Europe. Its aim is to develop new universal procedures for the correct design of pre-cast concrete building joints and structures potentially exposed to earthquakes.