Health monitoring and rehabilitation of a concrete structure using intelligentmaterials

Abstract

This paper presents the concept of an intelligent reinforced concrete structure (IRCS) andits application in structural health monitoring and rehabilitation. The IRCS hasmultiple functions which include self-rehabilitation, self-vibration damping, andself-structural health monitoring. These functions are enabled by two types ofintelligent (smart) materials: shape memory alloys (SMAs) and piezoceramics. In thisresearch, Nitinol type SMA and PZT (lead zirconate titanate) type piezoceramics areused. The proposed concrete structure is reinforced by martensite Nitinol cablesusing the method of post-tensioning. The martensite SMA significantly increasesthe concrete’s damping property and its ability to handle large impact. In thepresence of cracks due to explosions or earthquakes, by electrically heating the SMAcables, the SMA cables contract and close up the cracks. In this research, PZTpatches are embedded in the concrete structure to detect possible cracks insidethe concrete structure. The wavelet packet analysis method is then applied as asignal-processing tool to analyze the sensor signals. A damage index is defined todescribe the damage severity for health monitoring purposes. In addition, bymonitoring the electric resistance change of the SMA cables, the crack widthcan be estimated. To demonstrate this concept, a concrete beam specimen withreinforced SMA cables and with embedded PZT patches is fabricated. Experimentsdemonstrate that the IRC has the ability of self-sensing and self-rehabilitation.Three-point bending tests were conducted. During the loading process, a crack opensup to 0.47 inches. Upon removal of the load and heating the SMA cables, thecrack closes up. The damage index formed by wavelet packet analysis of the PZTsensor data predicts and confirms the onset and severity of the crack during theloading. Also during the loading, the electrical resistance value of the SMA cablechanges by up to 27% and this phenomenon is used to monitor the crack width.