Advances in Radio Frequency Identification (RFID) technology, in Micro-Electro-Mechanical Systems (MEMS), in lower-power wireless networking and in computation give hopes for a new generation of tiny, cheap, networked sensors that can be ‘sprayed’ on buildings to provide quantitative information on the structure’s physical state while in service. This can be used to assess the structural condition and aid decision making on retrofit, refurbishment and maintenance so that safety can be attained, and material use and costs can be reduced.
The objectives of this work are:
- To integrate MEMS-based sensors and a RFID tag in a single package of small size that will be attached to concrete buildings to measure acceleration and/or strain that will be transmitted to a remote base station using a wireless interface.
- To develop a Decision-Support-System (DSS) for proactive remedial measures under operating conditions and rehabilitation after an earthquake damage.
- To evaluate the system in ‘1’ and the DSS in ‘2’ in a structural laboratory.
- To field test an integrated package of the system in ‘1’ and the DSS in ‘2’ on an actual building.
The proposed system will be used in concrete buildings like schools where information will be sent wirelessly, to a central location (e.g. ministry of education), to be processed. It will result in lower maintenance cost, since problems are cheaper to fix when they first appear, and an increase in safety. The impact on safety will be greater after an earthquake where it is essential to have a quick estimate of the building structural condition. Moreover, it will transform the SME dominated building rehabilitation sector into an advanced knowledge sector, enhance the competitiveness of European SMEs, reduce time to assess the structural condition of a building in service and decide on remedial measures, promote sustainability, offer services with a high value added and enable the entrance of MEMS European SMEs to the large building market.
Wireless technology to monitor buildings
An EU-funded project successfully developed innovative, low-cost and highly reliable sensors capable of self-diagnosing and assessing optimal rehabilitation of buildings after earthquake damage.
As soon as a building is constructed, it starts to age. Buildings require safety inspections throughout their life and to evaluate their structural condition, especially after earthquakes. However, such activity can be severely hindered by the difficulty of gaining access to all relevant areas in a building while it remains in use.
Current structural monitoring systems employ conventional cables to allow sensors to communicate their measurements to a central processing unit. However, they have high installation costs and leave wires vulnerable to ambient signal noise corruption. In the EU-funded project http://www.memscon.com/ (MEMSCON) (Radio frequency identification tags linked to on board micro-electro-mechanical systems in a wireless, remote and intelligent monitoring and assessment system for maintenance of constructed facilities), scientists integrated microelectromechanical systems with a radio frequency identification tag into a single, tiny and cheap package.
The project employed acceleration and strain sensors to measure the forces as the building moves or vibrates, and to determine the strength of the construction materials. Measurement data are sent to a remote base station through a wireless interface.
Each sensor node is individually supplied by a battery. The acceleration sensors are activated only in case of seismic events and the strain sensors on a periodic basis, thus achieving low power consumption.
Along with the sensors distributed all over a building, the MEMSCON system includes a decision-support system (DSS). Accepting the sensor inputs, the system assesses the structural condition of the monitored building and selects the optimal remedy measures. The DSS includes an expert system with a user-friendly interface and knowledge bases. The end user can thus retrieve current and historical data from the knowledge bases, while examining different scenarios for hypothetical unsafe situations through real-time alerts.
MEMSCON's newly developed system enables engineers to precisely determine the structural state of a building, decreasing the time to assess the situation and decide on remedial measures. The system is not only suitable for commercial and residential buildings but could also be applied to monitoring the condition of bridges and roads.