روش جديد تشخيص آسيب بر مبناي تبديل موجك در قاب هاي خمشي ساختماني

A New Wavelet Based- Method for Damage Detection of Moment-Resisting Frame Structures

در اين تحقيق، روشي جديد بر مبناي پردازش سيگنال با استفاده از تبديل موجك براي تعيين زمان و موقعيت وقوع آسيب، در قاب هاي خمشي ارايه شده است. اغلب روش هاي قبلي تعيين زمان و مكان آسيب براساس اندازه گيري تغييرات مشخصات ارتعاشي سيستم نظير بسامد و مدهاي نوسان با استفاده از تبديلات فوريه، فوريه‌ي زمان كوتاه، و موجك بوده است. بنابراين، به مشخصات سازه‌ي قبل از آسيب هم نياز است. در روش پيشنهادي، مستقيماً از پاسخ دوراني گره هاي قاب يعني دوران ، سرعت زاويه‌يي، و شتاب زاويه‌يي براي استخراج اطلاعات مربوط به آسيب استفاده شده است. اين توابع حاوي اطلاعات بيشتري نسبت به ديگر پاسخ ها هستند، به طوري‌ كه مي توان تحليل آسيب را براساس اولين سطح تجزيه‌ي موجك انجام داد.

In this study, in order to determine the time and location of damage occurrence in moment-resisting frames a method based on general concept of signal processing methods is presented. Most of the previously presented methods aimed at finding the time and location of damage by considering occurrence changes in structural responses via using Fourier, Short time Fourier or wavelet transform methods. Vibration properties of the system may be addressed as vibration modal frequencies or modal shapes of the structure. In the proposed method, wavelet analysis of more complex responses of the structure, i.e. rotational, angular velocity or acceleration responses of the joints (nodes of the frame) is employed to extract information about damage. These functions contain more information, such that wavelet analysis may be conducted based on the only first level of signal decompositions. To determine location of damages, the concept of amplitude spectrum is used, which are achieved from comparison of the amplitude spectra of the rotational responses of the two adjacent nodes. Since, by occurring damages there is a large difference between these amplitude spectra, there is no doubt about finding location of damages in this method. In this research there is no need to know the primary system properties, and this is the main advantage of the method. The other advantage is the time of damage is achievable because time and location of damage is directly computed from the measured earthquake responses there is no need to conduct any (ambient or forced) vibration tests. Extensive analyses indicate accuracy and power of the proposed method to successful determination of the time and location of damages during different loadings. According to ability of this method to detect specifications of damages in early stages, it is recommended for health monitoring of important structures, which their performances are strongly considered during and after strong ground motion earthquakes.