دانلود رایگان مقاله لاتین ویبراتور مصنوعی از سایت الزویر
عنوان فارسی مقاله:
پژوهش آزمایشگاهی روش سنجش ساختاری با استفاده از ویبراتور دقیق مصنوعی
عنوان انگلیسی مقاله:
Laboratory experiment of the structural sensing method using the accurate artificial vibrator
سال انتشار : 2015
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مقدمه انگلیسی مقاله:
1. Introduction
Much of the infrastructure in Japan was developed during the period of rapid economic growth in the 1960s. Some of the structures involved are now more than 50 years old; consequently, it is essential that they be monitored in order to ensure that they are safe [1,2]. Inspections to evaluate the durability and service life of such 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 their durability. To measure the change in crack width and to prevent resultant damage, it is necessary to establish techniques for monitoring the crack behavior (e.g., [3,4]). Most existing approaches in this area are hand-sketch based, and crack openings are often evaluated using measuring magnifiers or crack width rulers; therefore, conventional measurement methods are manual, which may lead to nonobjective evaluation. Fiber optic sensors are also being used for crack monitoring. This technique does not utilize visual inspection and achieves measurements with accuracy similar to the standard strain gauges and extensometers; however, the cost of the data readout equipment used in applications coupled with installation and connection of the acquisition systems is very high (e.g., [5,6]). In contrast to wired systems, wireless systems require no cables for data transfer and are known for their low cost of deployment; however, their lifetime is limited by their battery-operated sensing devices (e.g., [7,8]). This paper proposes a new crack monitoring measurement technique based on digital image processing and photogrammetry that overcomes the challenges outlined above. A variety of digital image processing technology based measurement systems have been developed. The majority of these systems recognize the number of the pixels in a crack image reflected in the image as the crack width, and utilize image processing techniques such as binarization processing to facilitate counting of the number of the pixels in the crack image [9–13]. However, because the pixels of the crack image reflected in the image vary significantly depending on the photographing conditions, especially lighting, it is difficult to measure the change in crack width with high accuracy in the actual field. Moreover, photogrammetry based measurement systems are not very popularity because it utilizes a complicated process in which images need to be taken from various camera positions [14–17]. In our proposed technique, reflective targets are established as gauges at measurement points along both sides of a crack, and the two-dimensional displacement of the crack—tensile and shear displacement—is calculated based on the coordinates of these targets using only one image, captured from any arbitrary position. (1) Measurement can be performed using only a digital camera, reflective targets, and a PC, keeping costs very low, as low as that of the conventional photogrammetry method. However, unlike the conventional photogrammetry method, measurement is performed using only one captured image, as opposed to multiple images being required. (2) The measurement values of the crack width can be calculated independent of the lighting conditions, unlike the conventional image processing method, because the proposed technique recognizes the distances between the circles of the targets as the crack width.
کلمات کلیدی:
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