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Computers and Concrete Volume 31, Number 4, April 2023 (Special Issue) pages 293-306 DOI: https://doi.org/10.12989/cac.2023.31.4.293 |
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Smart monitoring system using electromagnetic waves to evaluate the integrity of reinforced concrete structural elements |
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Jong-Sub Lee, Dongsoo Lee, Youngdae Kim, Goangseup Zi and Jung-Doung Yu
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| Abstract | ||
| This study proposes and demonstrates a smart monitoring system that uses transmission lines embedded in a reinforced concrete structure to detect the presence of defects through changes in the electromagnetic waves generated and measured by a time-domain reflectometer. Laboratory experiments were first conducted to identify the presence of voids in steel-concrete composite columns. The results indicated that voids in the concrete caused a positive signal reflection, and the amplitude of this signal decreased as the water content of the soil in the void increased. Multiple voids resulted in a decrease in the amplitude of the signal reflected at each void, effectively identifying their presence despite amplitude reduction. Furthermore, the electromagnetic wave velocity increased when voids were present, decreased as the water content of the soil in the voids increased, and increased with the water-cement ratio and curing time. Field experiments were then conducted using bored piles with on-center (sound) and off-center (defective) steel-reinforcement cage alignments. The results indicated that the signal amplitude in the defective pile section, where the off-center cage was poorly covered with concrete, was greater than that in the pile sections where the cage was completely covered with concrete. The crosshole sonic logging results for the same defective bored pile failed to identify an off-center cage alignment defect. Therefore, this study demonstrates that electromagnetic waves can be a useful tool for monitoring the health and integrity of reinforced concrete structures. | ||
| Key Words | ||
| electromagnetic waves; integrity evaluation; reinforced concrete structure; smart monitoring; time-domain, reflectometry | ||
| Address | ||
| Jong-Sub Lee, Dongsoo Lee and Goangseup Zi: School of Civil, Environmental and Architectural Engineering, Korea University, Seoul, 02841, Korea Youngdae Kim: Department of Civil and Environmental Engineering, University of Illinois Urbana-Champaign, IL, 61801, USA Jung-Doung Yu: Department of Civil Engineering, Joongbu University, Goyang, 10279, Korea | ||