دانلود رایگان مقاله بهبود روش فتوگرامتری رقومی برای نظارت کرک

Abstract

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.

5. Conclusions

In this paper, we proposed a technique for measuring crack displacement using a digital camera image. In the proposed technique, reflective targets are established at measurement points around the crack as gauges and digital camera images of the targets are processed by photogrammetry and image processing. The results of experiments conducted to verify measurement accuracy and precision show that it is possible to take measurements with a high degree of accuracy/precision by adjusting the photographing condition of the proposed method, although a longer camera distance tended to produce slightly larger accuracies and precisions. In addition, measurement results obtained from an actual tunnel demonstrate that cracks in the tunnel wall can be identified through simple measurements. The measurements for a period of one year reveal that the tendency of crack displacement agrees with the extensometer measurement results. Furthermore, this result shows that measurement of only the cracks in the slide plane is adequate and the proposed method could reduce the labor and time required for conducting measurements. There are still some things we have to settle to establish a new measurement system featuring simple measurement work and a high degree of accuracy/precision. In this paper, the targets were designed with microscopic glass beads arranged in four circles. Is it possible to obtain better accuracy/precision under similar photographing conditions by increasing the number of circles on the target? All images were captured using a 13 MP digital camera, but does our proposed measurement system allow free selection of the digital camera? When we compress digital image data at a high compression rate, does the measurement accuracy/precision change? We plan to do further research in response to the requirements of actual sites with the aim to complete the proposed measurement system.