Experimental model analysis of cracked tanks containing fluid Sepehr Batebi sepehr.batebi@cv.iut.ac.ir September, 2020 Department of Civil Engineering Isfahan University of Technology, Isfahan 84156-83111, Iran Degree: M.Sc Language: Persian Supervisor: Dr. Payam asadi. Email address: asadi @cc.iut.ac.ir All structures are generally exposed to damage during their longevity. Concerning this fact, diagnosing the damage and providing a suitable repair solution seems to be indispensable. Liquid storage tanks are regarded as sensitive structures to damage. Such structures might be damaged due to stroke, corrosion, and fatigue, which engenders financial and human losses. However, repairing small damage in storages is not costly. One of the most common damages in tanks is creating and expanding cracks in the tank wall. Modal analysis is one of the proposed methods determining the damages in tanks, which can detect the geometric position and depth of cracks through the use of vibration data. In this study, the perfect and cracked tanks containing fluid is evaluated by modal analysis for the first time. For this purpose, the experimental study conducts on a 80×80×1cm glass wall tank. One of the most critical issues in tanks' construction is the creation of retaining support at the bottom of storage. The solid concrete foundation is so that 10 cm from the glass's height be in the concrete base. Firstly, the perfect tank is tested as a reference specimen. Afterward, two cracked tanks with different crack locations are investigated. The ratio of crack length to tank length is considered 0.6, and the ratio of maximum crack depth to glass thickness is 0.6. The cracks' height from the tank base for the first and second cracked rank are 31 and 47 cm, respectively. Each tank is studied in 6 different water levels (one of the levels is zero) to investigate the effect of water level on the modal results. The tank is filled by water up to heights of 0, 24.5, 41, 57, and 76 cm. Therefore, natural frequencies and mode shapes are extracted for each tank at different water levels by modal experiments. The results reveal that cracks in the tank reduce natural stiffness and frequency. The lower the crack height relative to the tank floor leads to a more significant decrease in natural frequencies. Furthermore, natural frequencies decrease with increasing water depth in the tank. From the results of this study, cracking at a height higher than the bottom of the tank in the cracked tank caused a further reduction of the first and second natural frequencies compared to cracked tanks with a crack height at the lower part. Also, cracks at lower altitudes in cracked reservoirs reduced the natural frequencies of the third, fourth and fifth compared to cracked reservoirs with crack heights at higher altitudes. Keywords: structures' modal experiment, cracked tank, glass tank, natural frequency, mode shape.