Current Smart Materials Send Orders for Reprints to reprints@benthamscience.ae   Costas Providakis a,* , Stavros Tsistrakis a , Maristella Voutetaki a , John Tsompanakis b , Maria Stavroulaki a , John Agadakos a , Eleftherios Kampianakis a , George Pentes a and Evangelos Liarakos a a School of Architectural Engineering, Technical University of Crete, Chania, Greece; b School of Environmental Engi- neering, Technical University of Crete, Chania, Greece Abstract: Background: A major concern of the current concrete structures technol- ogy is to develop systems that can monitor their own structural integrity condition in real time. This paper presents the development of a portable and innovative wireless damage monitoring system based on an alternative consideration of electromechani- cal impedance concept, integrating PZT sensors/actuators transducers into the con- crete structures themselves. Methods: The proposed wireless monitoring system for active sensing is designed, built, tested and provided with all capabilities needed to perform an integrity as- sessment by means of the use of a Raspberry Pi single-board microcomputer as the core hardware element to control the whole system function. Results: It is found that the proposed alternative of the electromechanical impedance (EMI) technique associated with decision boundaries based on extreme value statistics is very sensitive to the damage in- troduced in concrete structures from their earliest stage. The tests run on the developed prototype prove that the proposed monitoring platform can actually be used to perform damage detection investigation with the required accuracy. Conclusion: Its effectiveness and low cost make this platform a very promising contribution towards the implementation of large-scale wireless structural health monitoring applications. A R T I C L E H I S T O R Y Received: February 19, 2016 Revised: August 22, 2016 Accepted: August 23, 2016 DOI: 10.2174/240546580166616083015 5120 Keywords: Concrete damage detection, electromechanical impedance method, extreme value statistics, Raspberry Pi, PZT sen- sor/actuator. 1. INTRODUCTION Electromechanical impedance (EMI) monitoring meth- odology has been proved that could be an effective alterna- tive experimental procedure for the damage detection of concrete structures even at very early-age stages. There are a lot of such kind of applications mainly taking into account simple concrete structures under various loading and artifi- cial damage conditions [1-17]. More specifically, the EMI technique has been utilized to monitor the strength gain of concrete structures using either surface bonded sensors [1-6] or embedded in the mass of the concrete [7-10]. Some focus of the work has also turned towards the reusability of the packaged sensors used for the concrete early age monitoring [11, 12]. Another field of research is the detection of damage *Address correspondence to this authors at the Laboratory of Applied Me- chanics, School of Architectural Engineering, Technical University of Crete, University Campus, Office : 141.B.85, Building of Sciences, P.O. Box: 73100, Chania, Greece; Tel: +30 (28210) 37 637 (office), +30 (28210) 37 631-632-640 (Lab); Fax: +30 (28210) 37866; E-mail: cpprov@mred.tuc.gr in concrete structures performing either cyclic compression tests in cubic specimens [9, 11, 12] or induced damage by bending or other means in larger scale structures like beams [13-15] or bridges [16]. Additionally Yang and Divsholi [15] studied the connection between the excitation bandwidth and the distance and type of damage. Finally, there have been studies for the creation of a wireless network using the Ana- log Devices AD5933 board [9, 17]. The most important advantage of EMI monitoring tech- nique is its efficiency to implement low budget hardware parts, such as piezoelectric (PZT) actuators and sensors. The measuring principle of this technique is that PZT transducers mechanically interact with the structure which host them. After the application of a harmonically vibrated voltage which acts as an input over the PZT surfaces, mechanical vibrations are transmitted through the PZT-host structure bonding interface which is used to monitor the damage in- troduction at early conditions. The host structure is mechani- cally reacting to the transmitted mechanical wave and this reaction is going to be monitored as PZT's output electrical Please provide corresponding author(s) photograph size should be 4" x 4" inches Current Smart Materials, 2016, 1, 49-62 49 RESEARCH ARTICLE An Innovative Active Sensing Platform for Wireless Damage Monitoring of Concrete Structures 2405-4666/16 $58.00+.00 © 2016 Bentham Science Publishers