Abstract—The purposes of hydraulic gate are to maintain the functions of storing and draining water. It bears long-term hydraulic pressure and earthquake force and is very important for reservoir and waterpower plant. The high tensile strength of steel plate is used as constructional material of hydraulic gate. The cracks and rusts, induced by the defects of material, bad construction and seismic excitation and under water respectively, thus, the mechanics phenomena of gate with crack are probing into the cause of stress concentration, induced high crack increase rate, affect the safety and usage of hydroelectric power plant. Stress distribution analysis is a very important and essential surveying technique to analyze bi-material and singular point problems. The finite difference infinitely small element method has been demonstrated, suitable for analyzing the buckling phenomena of welding seam and steel plate with crack. Especially, this method can easily analyze the singularity of kink crack. Nevertheless, the construction form and deformation shape of some gates are three-dimensional system. Therefore, the three-dimensional Digital Image Correlation (DIC) has been developed and applied to analyze the strain variation of steel plate with crack at weld joint. The proposed Digital image correlation (DIC) technique is an only non-contact method for measuring the variation of test object. According to rapid development of digital camera, the cost of this digital image correlation technique has been reduced. Otherwise, this DIC method provides with the advantages of widely practical application of indoor test and field test without the restriction on the size of test object. Thus, the research purpose of this research is to develop and apply this technique to monitor mechanics crack variations of weld steel hydraulic gate and its conformation under action of loading. The imagines can be picked from real time monitoring process to analyze the strain change of each loading stage. The proposed 3-Dimensional digital image correlation method, developed in the study, is applied to analyze the post-buckling phenomenon and buckling tendency of welded steel plate with crack. Then, the stress intensity of 3-dimensional analysis of different materials and enhanced materials in steel plate has been analyzed in this paper. The test results show that this proposed three-dimensional DIC method can precisely detect the crack variation of welded steel plate under different loading stages. Especially, this proposed DIC method can detect and identify the crack position and the other flaws of the welded steel plate that the traditional test methods hardly detect these kind phenomena. Therefore, this proposed three-dimensional DIC method can apply to observe the mechanics phenomena of composite materials subjected to loading and operating. M. H. Shih is with the Department of Civil Engineering, National Chi-Nan University, Pu-Li, Nantou 545 Taiwan (e-mail: iloveaachen@gmail.com) W. P. Sung is with the Department of Landscape Architecture, National Chin-Yi University of Technology, Taiping, Taichung 41170 Taiwan. (corresponding author to provide phone: 886-4-23935691; fax: 886-4-23930737; e-mail: wps@ ncut.edu.tw). Shih-Heng Tung is with the Department of Civil and Environmental Engineering, National University of Kaohsiung, Nan-Tzu, Kaohsiung 81148 Taiwan (e-mail: shtung@nuk.edu.tw). Keywords—Welded steel plate, crack variation, three-dimensional Digital Image Correlation (DIC). I. INTRODUCTION PEICAL geographical environment and poor geological conditions coupled with the steep and short river are hard to accumulate and drainage rainfall effectively in Taiwan. Especially, Taiwan is located in the Pacific seismic belt and storm-prone regions. It also does not attach importance to environmental conservation in the past, mountainside cultivation, resulting in land cannot be protected effectively. Otherwise, Taiwan will be affected by typhoons, heavy rain, earthquakes and drought and other natural disasters hit. In recent years, Taiwan Chi-Chi earthquake caused loosening of soil and stone of mountains or even collapse. In addition, effects of global warming are going to ferment gradually to induce El Nino and anti-El Niño continue to recur, causing heavy rainfall frequency and intensity will vary with the Earth's temperature rises gradually; such as torrential rains of typhoon Morakot caused landslides in mountainous areas, hit southern Taiwan, causing heavy losses of lives and property of the people, it also leads to water storage capacity of Tseng-Wen reservoir etc. drastically reduce and even threaten the safety of reservoir. Landslide of National Road 3 at Taipei-Keelung section happened without any sign to cause losses of human life. Otherwise, 311 strong earthquake causes tsunami in Japan on 2011. Pakistan earthquake of July 2013, with the exception of houses toppled and loss of human life, and even reached a small island off the coast. These exceptionally natural disasters caused by climate disaster and aftermath yet very serious, these are the effects and consequences of global warming. Hydraulic gate is applied in water dam to store and drain water. High tensile strength of steel plate is used as constructional material of hydraulic gate. But, there are maybe some cracks and rusts, induced by the defects of material, bad construction and seismic excitation and under water respectively, thus, the mechanics phenomena of gate with crack are probing into the cause of stress concentration, induced high crack increase rate, affect the safety and usage of hydroelectric power plant. In fact, most of the damage is progressive, meaning that there are usually signs of long-term, such as unusual changes in the development of cracks, seepage. The test and maintenance of hydraulic machinery can reflect these kind problems. Hydraulic gate includes rail, chair, water seal, and guide such groups stand gate slot and buried in concrete. Gate rubber seal around the door, align it with the door frame seal tight, door and gate Developing Three-Dimensional Digital Image Correlation Method to Detect the Crack Variation at the Joint of Weld Steel Plate Ming-Hsiang Shih, Wen-Pei Sung, Shih-Heng Tung S World Academy of Science, Engineering and Technology International Journal of Civil and Environmental Engineering Vol:9, No:7, 2015 918 International Scholarly and Scientific Research & Innovation 9(7) 2015 scholar.waset.org/1307-6892/10002909 International Science Index, Civil and Environmental Engineering Vol:9, No:7, 2015 waset.org/Publication/10002909