تشخيص ترك در صفحات فولادي غشايي و خمشي براساس تئوري پري‌دايناميك با استفاده از الگوريتم بهينه¬يابي فراابتكاري

Crack detection , membranes an‎d plates , Peridynamic theory , optimization algorithm

Crack detection in steel membranes an‎d plates based on Peridynamic theory using metaheuristic optimization algorithm

مهندسي عمران

Abstract The existence of crack in structures is considered one of the types of damage that many methods, including theoretical an‎d non-theoretical methods, have been introduced to detect them. Due to the complexity of modeling the crack line in the structure, those theoretical methods that require analysis of the cracked structure for detect of cracks, are limited. In this thesis, for the first time a model-based non-theoritical method that is a combination of Peridynamic theory an‎d an upgraded metaheuristic optimization algorithm is proposed for crack detection in steel plates an‎d beams with the aim of simple modeling, relatively high accuracy in modeling the cracked structure, highly accurate an‎d reliable results, an‎d also high convergence speed. Unlike conventional methods, the Peridynamic theory has high capability of modeling the crack in structure an‎d is used to analize the cracked structure. Also, the charged system search algorithm (CSS) is chosen in the crack search step. In order to increase the accuracy an‎d reliability of the results of this algorithm, a special search step has been added to it (UCSS). Unlike many previous studies, there is no limitation in the direction of the crack in this research. The objective function in crack identification problem is defined based on the difference in displcament at different points of the structure. Before implementation of crack detection method, the optimal position of the displacement recording sensors as well as the external loads applied, are determined. At first, the mensioned method is eva‎luated to detect cracks in a rectangular plate in different scenarios. The method is then tested on new scenarios in which the crack orientation is similar to the previous scenarios but the crack length is reduced. Next, the method is applied to several beams with different restraint conditions. In order to more investigation of power of added step in the proposed method, four other optimization algoritms search the crack in beams. In the next section, crack detection in bending plates is also investigated. Finally, several examples of crack detection solved by one of the thesis references with another method, are considered. The noise effect on crack identification method in examples of beams an‎d plates is considered .To reduce the computational cost of proposed crack detection method, the parallel processing capability is used in the implementation of the structure analysis part. The results obtained by the crack detection method show that the coordinates of crack line founded by this method in plates an‎d beams have a very good agreement with the real crack an‎d the crack detection in noisy environmental conditions is also acceptable. The search power of the UCSS algorithm has also been higher compared to the mentioned algorithms. The proposed method is also very accurate in identifying cracks defined in membranes whose length is 10%. The identification accurate of crack coordinates using the proposed method in this thesis on examples provided by one of the references was also higher than the methods used in that reference. Keywords: Crack detection, membranes an‎d plates, Peridynamic theory, optimization algorithm

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