Piezoelectric based concrete strength monitoring model
Concrete strength monitoring, providing information related to the readiness of the structure for service, is crucial to the safety and resource planning in the construction industry. The advent of smart material, namely piezoelectric (Lead Zirconate Titanate, PZT) transducer, has the potential of o...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English English |
| Published: |
2017
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| Subjects: | |
| Online Access: | https://eprints.ums.edu.my/id/eprint/38020/1/24%20PAGES.pdf https://eprints.ums.edu.my/id/eprint/38020/2/FULLTEXT.pdf |
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| Summary: | Concrete strength monitoring, providing information related to the readiness of the structure for service, is crucial to the safety and resource planning in the construction industry. The advent of smart material, namely piezoelectric (Lead Zirconate Titanate, PZT) transducer, has the potential of overcoming some shortcomings of the conventional structural health monitoring (SHM) techniques, which are timeconsuming, labor and cost-intensive, requiring bulky equipment and exposing inspectors to the dangerous environment. Despite the superiority of PZT based SHM techniques, studies conducted thus far are non-parametric, qualitative and lab-based in nature, which limits its potential use in real-life application. This is one of the key limitations of the current smart based monitoring technology, which a direct and accurate strength prediction model is unavailable. The lack of physical model and understanding limits their development and potential in real-life applications. In this research, a novel parametric based, semi-analytical model was developed for the surface bonded PZT based wave propagation (WP) technique for strength evaluation of concrete throughout the curing process. Mechanical parameters of the mortar specimen were mathematically derived from the surface wave (R-wave) and pressure wave (P-wave) using elastic wave equations. These parameters were then empirically correlated to the strength. A proof-of-concept strength calibration chart was finally developed using the semi-empirical model. The model was found to be very robust as it could be generalized to account for different water to cement (W /C) ratio. The performance of the WP technique was then compared to the electromechanical impedance (EMI) technique and the conventional techniques, such as the ultrasonic pulse velocity (UPV) and rebound hammer (RH) test. Results showed that the WP technique performed equally well as the conventional counterparts. The proposed technique is also advantageous over the embedded based WP technique and UPV test, in terms of its capability to capture two types of waves for the evaluation of the dynamic modulus of elasticity and Poisson's ratio. Despite promising performance based on lab-based study, various practical issues affecting the real-life application and the reliability of the technique has not been addressed. In this research, a series of experimental studies were performed to investigate the aforementioned problems, in an attempt to reduce the gap between laboratory and real-life application. Some key issues related to the practical application of this technique were identified and studied, including the consistency and repeatability of the sensor electrical signatures, waveform pattern, frequency selection, the effect of varying PZT transducer' spacing, the sizes of PZT transducer, surface roughness of the host structure, the environmental condition and the effects of different coarse aggregates. Such understanding is essential to serve as guidelines for future design optimization of a more effective PZT based WP technique. Results indicated that the performance of the WP technique was reliable and consistent across different specimens, with different sizes and spacing of PZT transducers. A separate study was finally conducted to verify the applicability of this technique on the heterogeneous concrete specimen. A finite element (FE) model was proposed to have a better understanding of the behaviour of the PZT based WP technique. The finding from the research has patched up the gap between theory and practice of a PZT based monitoring system for concrete strength by using WP technique, which can be a useful tool in real-time concrete strength prediction, optimizing the time of falsework dismantling, at the same time, ensuring the quality of concrete structure, improving its safety as well as bringing huge savings in terms of time and cost to the construction industry. |
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