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Nishi-Tokyo-shi, Japan

Nishiyama S.,Okayama University | Minakata N.,Kyoto University | Kikuchi T.,JP Design Co. | Yano T.,Kyoto University
Advanced Engineering Informatics | Year: 2015

Inspections to evaluate the safety, durability, and service life of aging infrastructure play an important role in determining the countermeasures that need to be taken, such as reinforcement, repair, and reconstruction. In infrastructure containing concrete, such as bridges and tunnels, crack widths and patterns on surfaces are two of the most important signs used to estimate durability. Current conventional techniques used for this purpose suffer from challenges such as tediousness, subjectivity, and high cost. Consequently, a new measurement technique that overcomes these challenges while measuring crack displacement with high accuracy and precision in aging civil engineering structures is needed. In this paper, we proposed a technique for measuring crack displacement using a digital camera image. In the proposed technique, reflective targets are established around both sides of a crack as gauges, and subsequent digital camera images of the targets are subjected to image processing to determine the displacements of the targets. These displacements can be measured using images captured from any arbitrary camera position. The results of experiments conducted to verify the efficacy of the proposed method show that crack displacements of less than 0.10 mm can be measured with high accuracy and precision using digital images captured at a distance of 10.0 m from the target, while less than 0.20 mm changes in the tensile displacement of the crack can be measured from an image captured at 25.0 m from the crack. Measurement results obtained from a tunnel are also presented to show that cracks in the walls of an actual tunnel can be identified through simple measurements. These measurements, taken over a period of one year, indicate that the tendency of crack displacement and slide movements are in close agreement. © 2015 Elsevier Ltd. All rights reserved.

Nojima J.,JP Design Co. | Arai M.,JP Design Co. | Mizobuchi T.,Hosei University
RILEM Bookseries | Year: 2012

Presence of chloride ions in cover concrete leads to an enhanced deterioration of reinforced concrete structures. Prediction of the resultant damage in early stages of development is not possible, unless the distributions of chloride ions across the concrete section are known. This paper presents an on-going study of evaluating such distribution by a non-destructive method using electromagnetic wave. The technology is introduced in a separate paper in the symposium, shows in laboratory experiments its applicability to structures whose concrete properties are known. The ability to estimating the said distribution in cross section in existing concrete structure has been investigated in field tests and the method to be equally usable has been found by modifications of the method based on actual concrete properties in question. Once established, the method will provide a valuable means of readily collecting, not a limited and point-based data from cores, but information of area-wide chlorine ions non-destructively. This should, in turn, allow the owner of the concrete structure to identify chlorine deterioration at an early stage and to formulate effective strategies against the resultant damage. © RILEM 2013.

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