ارزيابي و مقايسه‌ي شاخص‌هاي مكان‌يابي خسارت در قاب‌هاي سه بعدي بتني

ASSESSMENT AND COMPARISON OF DAMAGE LOCALIZATION INDICES IN THREE DIMENSIONAL REINFORCED CONCRETE FRAMES

تشخيص خسارت در سازه‌ها به دليل تاثير در مسايل اقتصادي و مديريت بحران پس از زلزله، مورد توجه محققان قرار گرفته است . بسياري از مطالعات، در طيف وسيعي از روش‌هاي تشخيص خسارت، مبتني بر پارامترهاي ارتعاشي است. مزيت مهم اين روش قابليت شناسايي خسارت در سازه‌هاي بزرگ است. اغلب مطالعه‌هاي تشخيص خسارت با روش‌هاي ارتعاشي به سازه‌هاي يك يا دو بعدي اختصاص دارد. در سازه‌هاي سه بعدي اين مطالعات محدودترند. در اين نوشتار توسعه‌ي روش‌هاي ديناميكي خصوصاً روش انحناي مودي و روش‌هاي مبتني بر انرژي كرنشي مودال در قا‌ب‌هاي سه بعدي بتن مسلح مطالعه شده است كه بر مبناي نتايج، شاخص‌هاي تغيير انحناي مودي در درجات آزادي چرخشي و تغيير انرژي كرنشي مودال به ازاي مولفه‌ي محوري ماتريس سختي، دقت قابل قبولي در مكان‌يابي خسارت دارند.

Damage detection and assessment in structures have increasingly received the attention of researchers, due to their role in economical aspects and emergency management after earthquakes. The majority of studies on various methods of damage detection rely on the measured vibration response parameters of structures, as a result of their applicability to large and complex structures. While most research has concentrated on one or two dimensional structures, there are few studies available in the literature on three dimensional structures. The purpose of this study is to apply methods based on modal parameters to three dimensional reinforced concrete frames. To achieve this objective, numerical results are generated for a 3D one story frame with five different scenarios of damage. The application of vibration methods, especially “mode shape curvature”, and methods based on “modal strain energy” in damage localization, are also investigated. To implement these methods requires only a small number of mode shapes identified from both damaged and baseline structures. The mode shapes are divided according to their degrees of freedom in order to improve the accuracy of the mode shape curvature indicator method. In addition, the accuracy of the modal sensitivity method has been investigated for two behavioral modes (axial and flexural) of structures. Furthermore, the stiffness matrix has been decomposed to its components (axial and transversal terms) in methods based on modal strain energy. It should be noted that the accuracy of the results is related to damage location. On the other hand, various kinds of indices used in this study have noticeable differences in elements, which are in the proximity of the primary damage location. The results reveal that the mode shape curvature change of rotational degrees of freedom and modal strain energy change associated with the axial term of the stiffness matrix have an acceptable accuracy in damage localization. In addition, it can be concluded that localization of damage at the base of columns via indices applied in this study is more accurate compared to other locations.