SENSOR BASED STRUCTURAL HEALTH MONITORING OF CONCRETE STRUCTURES Othman Sidek, S.A.Quadri and Hassan bin Afzal Collaborative µ-electronic Design Excellence Centre Universiti Sains Malaysia Presented in Université de Sherbrooke
A special kind of sensor that uses optical fiber either as the sensing element ("intrinsic sensors"), or as a means of relaying signals from a remote sensor to the electronics that process the signals ("extrinsic sensors").
Fiber Bragg grating (FBG)
A type of distributed Bragg reflector constructed in a short segment of optical fiber that reflects particular wavelengths of light and transmits all others.
Type of silicone elastomer or silicone rubber which contains very useful properties as a base material for various sensing applications.
Process of combining inputs from various sensors to provide a robust and complete description of an environment or process of interest.
Decentralized Kalman filter
Robust means to fuse heterogeneous data used as optimal solution to many tracking and data prediction.
National Building Research Institute (NBRI)
Standard testing method employed to accelerate AAR expansion with different level of alkali concentrations.
Multi-layer perceptron (MLP) network
Artificial neural network (ANN) which is ideally suited to identify non linear system dynamics.
In reinforced concrete infrastructure, the steel corrosion occurs due to penetration of chloride ions or carbon dioxide.
The objective of the present investigation is to develop a low-cost FOS based sensing technology for detecting steel corrosion inside reinforced concrete infrastructures and also measure the level of the corrosion occurred in the specific section so necessary steps can be taken effectively.
A novel FOS based sensing method for detecting the onset of steel corrosion inside reinforced concrete structure with particular application on concrete structures is being studied, developed and experimented in the laboratory.
The specific sensing method developed will be tested in various conditions and also embedded in cement mortar to demonstrate the feasibility of corrosion sensing.
Standard Electrical Wireless Sensing Method to Detect Corrosion
The first and second figure shows the basic wireless sensors without and with switch technology for enhanced detection. After applying the switch (shown in figure-2), the detection accuracy has been improved(shown in the graph).
There is only one switch in this sensor, which can only indicate whether the steel wire breaks or not and only two corrosion states of the reinforcement can be monitored. Whether or not more corrosion states of the reinforcement can be indicated when more switches with different diameters of steel wires are added into the sensor and how to obtain the relationship between the diameter of the steel wire and the loss of the weight of reinforcement need to be studied further.
Schematic Diagram of EFOCS Here, the first figure represents Typical layout of corrosion sensors in reinforced concrete structure and the next figure shows the Photograph of fiber optic corrosion sensor. Source : J. Gao et al. (2011)
Performance Enhancement by Applying PDMS Coating Material in FOS
Polydimethylsiloxane (PDMS) is a very interesting and exceptional type of silicone elastomer or silicone rubber which contains very useful properties as a base material for various sensing applications.
In the recent years, FOS based fiber Bragg grating (FBG) sensors have been studied, researched and experimented extensively for sensing and measuring several types of physical parameters such as strain, bending, pressure, temperature, and chemicals
It has a unique ability of cross-linking without any sort of difficulty makes it one of the primary choices for numerous micro- and nano- cast applications as a base material or coating material. In case of fiber optic sensing technology, PDMS can be used as a coating material to enhance the sensing and measurement performance for corrosion detection in concrete structures.
Proposed PDMS-coated FBG can be used as a simple, convenient, and durable chemical sensing element with a high sensitivity, compared with conventional FBG sensors requiring an evanescent wave coupling.
Source : Chang –sub Park et al. (2010)
Heterogeneous Multi sensor Data fusion system A novel integrated multi sensor data fusion approach in structural health monitoring is proposed to monitor AAR reaction in concrete structures
To assess :
Structural integrity of concrete structure.
Damage at surface level.
Damage at internal level.
To find :
Total amount of cracking in terms of length and width.
Correlation between surface damage level with internal damage level.
Correlation between overall damage level and AAR gel concentration.