چكيده فارسي :
در اين تحقيق شناسايي محل و ميزان آسيب در سازه با استفاده از الگوريتم بهينه‌سازي زنبور عسل مصنوعي بررسي شده است. تعيين ميزان و محل خسارت در سازه‌ها با استفاده از بازرسي ميداني و چشمي فرآيندي پرهزينه است، لذا با استفاده از روشهاي تحليلي علاوه بر سرعت دسترسي قابل ملاحظه، هزينه‌هاي تعيين محل و ميزان آسيب نيز كاهش مي‌يابد. با دانستن فركانس‌ها و شكل‌هاي مودي سازه آسيب‌ديده كه از نتايج اندازه‌گيري بدست مي‌آيد و همچنين فرض عدم تغيير ماتريس جرم در سازه سالم و آسيب‌ديده، ماتريس سختي به گونه‌اي تعيين مي‌شود كه در قضيه مقادير ويژه ماتريس جرم و سختي سازه آسيب‌ديده صدق نمايد. حل مساله از روش معكوس نيازمند سعي و خطاي متعددي تا رسيدن به جواب قابل قبول مي‌باشد ولي استفاده از الگوريتم‌هاي بهينه‌سازي عددي مي‌تواند به گونه‌اي فضاي پاسخ را جستجو كند كه تعداد سعي‌هاي لازم بسيار كم و محدود گردد. در اين پژوهش الگوريتم زنبور عسل مصنوعي براي تعيين ماتريس سختي سازه آسيب‌ديده استفاده مي‌گردد. همچنين روش SEREP براي فشرده‌سازي ماتريس جرم و سختي به منظور كاهش حجم محاسبات بكارگيري مي‌شود. براي ارزيابي اين روش، دو خرپاي مسطح و فضايي و يك قاب مسطح هر كدام با دو سناريوي خسارت درنظر گرفته مي‌شود. نتايج بررسي نشان مي‌دهد كه اين روش توانايي و دقت قابل‌قبولي در تعيين ميزان و محل آسيب در سازه با وجود اطلاعات فركانسي و شكل مودي نويزدار دارد.
چكيده لاتين :
In recent years, damage identification of structures becomes more attractive for researchers in order to quantify the condition of structural system during service life. Moreover, identifying the damage location and severity is very important after disasters such as earthquake and terrorist attak. Structures can also be damaged by normal activity such as corrosion, aging, fatique, wind, waveload, etc. Therefore, the structural health monitoring is an emerging field to ensure good performance of structures. In this paper, identification of the location and severity of damages in structures are studied by analytical method using artificial bee colony optimization (ABC). In the analytical method, the mass and stiffness matrices of structure can be determined by the finite element procedure. Considering the stiffness matrix of healthy structure and that of the damage structure, the location and severity of the damage can be determined. It is assumed that the global mass matrix remains unchanged after the damage occurs in the structure. The natural frequencies and mode shapes of damaged structure can be obtained by measurement. In the study, the damage characteristics are known. Then by applying the eigenvalue equation, the stiffness matrix is determined for damaged structure. Finding the location of damage is introduced as an inverse problem. The conventional methods are very expensive and time consuming, while meta-heuristic methods are capable to solve complex optimization problems. Swarm intelligence algorithm introduces the collective behavior of social insects colonies to solve optimization problems. Artificial bee colony algorithm is an evolutionary computing method, which was developed, based on the intelligent foraging behavior of honeybee swarm. Each food source is considered as a possible solution. The location and quality of the nectar from the flower is related to the damage properties and fitness function, respectively. The dimension of every artificial employed bee is equal to the number of member of the structure. Then quality value of the food source is evaluated by the fitness function. The best fitness value is memorized in each search. When the fitness value is improved after a predefined iteration, the new possible solution will be considered. In the ABC process, the number of food source, the limit and the maximum cycle number are three control parameters. In the optimization problem, applying a proper objective function is one of the indispensable part of the process. Since the structural damage detection is a highly nonlinear problem, a proper objective function can detect the damage accurately and quickly. There are various methods for damage detection, which generally can be classified into two categories, static and dynamic method. Because of the efficiency of the dynamic method, the objective function is selected based on the dynamic technique, which utilizes the eigenvalue problem. In the mathematical equation of the objective function, the mass and stiffness matrix of healthy structure is defined by finite element method. The natural frequencies and mode shapes obtained by the measurement or modeling the structure. The stiffness matrix of damaged structure is determined with the optimization algorithm to minimize the objective function. In a measurement test, the used sensors cannot detect all of the degrees freedom of a structure, therefore the obtained information in measurement include a limited number of frequencies or mode shapes. In addition, to avoid a time consuming process, it may be decided to utilize only a limit number of frequencies obtained by the measurement. The system equivalent reduction expansion process (SEREP), which is an accurate and efficient technique of model reduction, is utilized in the paper. Moreover, the damage detection is examined through three numerical examples, plane and space truss and palne frame, each one has two damage scenarios, which include noisy measurement data. The results indicate that the proposed method is a powerfull procedure to detect damages in structures.
