دانلود ترجمه مقاله مطالعه شبیه سازی تشخیص آسیب در ساختمان های اسکلت برش فولادی
بخشی از ترجمه:
چارچوب‌های سازه‌ای هر دو نوع رفتار ارتجاعی و پلاستیکی رااز خود نشان می‌دهند که نوع رفتار آنها وابسته به بار وارده بر آنهاست. در مراحل اولیه‌ی تخریب زمین لرزه سیستم سازه‌ای در فاز ارتجاعی خود باقی می‌ماند اما هنگامی که این تخریب و بار وارده بیشتر می‌شود، این ستون بندی‌ها سازه را در مقابل ریزش حفظ می‌کنند. تعیین زمان و محل وقوع این خسارت‌ها بسیار مهم است. هدف کلی شیوه‌های قبلی همانند فوریه، فوریه ی سریع و یا تبدیل موجک‌ها یافتن زمان و مکان ایجاد این مفصل‌های تکیه گاهی است. این کار با استفاده از تغییر در محدوده‌ی واکنش‌ها و استفاده از ویژگی‌های ارتعاشی سیستم‌هایی همانند فرکانس لرزش و یا مدهای لرزش سازه صورت می‌گیرد. گر چه، این شیوه‌ها، در کاربردهای اولیه بسیار مؤثر نیستند زیرا ویژگی‌های لرزشی به طور عمده‌ای درابتدای تشکیل مفصل‌های تکیه‌گاهی تغییر نمی‌کنند. دراین تحقیق، از توانایی تبدیل موجک‌ها در به دست آوردن اطلاعات بومی درباره‌ی سیگنال‌ها برای تعیین زمان و مکان تشکیل مفصل‌های تکیه گاهی استفاده می‌شود. این سیگنال‌ها برای تعیین زمان و مکان تشکیل مفصل‌های تکیه گاهی استفاده می‌شود. این سیگنال‌ها همان واکنش‌های ثبت شده سازه‌ی در حال لرزش می‌باشند. نتایج به دست آمده نشان می‌دهند که شیوه‌ی پیشنهادی می‌تواند در تعیین زمان و مکان خسارت بدون استفاده از شیوه‌ها و مفاهیم پیچیده، مؤثر می‌باشند.
بخشی از مقاله انگلیسی:
Structural frames, demonstrate both elastic and plastic behaviour depending on their load. At early stages of earthquake loading structural systems remain in the elastic phase, but when the loading increases, plastic hinges form and affect the structural response. Determining the location and time of this damage is critical. The aim of previous methods such as Fourier, short time Fourier or wavelet transform was to find the time and location of hinge formation. This was conducted by changing response space, with the use of vibration properties of a system like vibration frequency or vibration modes of the structure. However, these methods are not very effective in early warning applications since the vibration properties do not change significantly at the beginning of plastic hinge formation. In this research, the capability of wavelet transform in extracting local signal information will be used to determine the time and location of plastic hinge formation. These signals are recorded responses of the structure under seismic excitation. The obtained results indicate that the proposed method can effectively determine the time and location of damage without employing complicated methods and concepts. Key words: Damage detection, plastic hinge, impulse response, shear frame. INTRODUCTION An estimation of damage in the building frames has two main targets: (I) determination of stability and serviceability of structures after the earthquake, (II) producing a priority scheme and timetable to repair the damaged parts. Also, as these estimations are often based on vibration responses of a system, substantive changes in response – e.g. natural frequency changes – are often the basis for damage detection. These changes are functions of intensity and location of induced damage. This means that less damage at the closer distance can have similar effects as more damage at farther away *Corresponding author. E-mail: f.raufi@srbiau.ac.ir. which makes detection more complicated. In any case, relative damage estimation is also useful because it can be the basis for choosing strategies to repair damaged areas. These behavioural changes are usually rooted in the change of material behaviour in one or several structural elements and will weaken element(s) and consequently the system as a whole. Modelling of damage is also an important point in determining structural behaviour. In proper modelling, damage should be formed in the loading process and increase with loading increments. In other words, it should be in agreement with real damage in the structure. The formation of plastic hinges in a specific section has these properties, so it can be a simple and appropriate model to track the behaviour changes in a section of the structural element. Plastic hinge behaviour is expressed in terms of forcedisplacement curves, e.g. moment-curvature. Having moment-curvature relations for a specific member, one can determine the level of plastic rotation capacity. Angular displacements of the plastic hinges at the ends of the beams and columns in a frame are important in the nonlinear dynamic analysis because they represent damage to the structure (Hui et al., 2004). A damage index based on the same idea was presented by Campbell et al. (2008), which is a quantitative parameter for estimating structural damage and damage in a member. Jankovic and Stojadinovic (2008) provided a damage index based on joint maximum plastic rotation for positive and negative rotation. The plastic ductility damage index is at the centre of the standards’ attention such as FEMA (2000) because of simplicity in calculation and tangible physical concept (Powell and Allahabadi, 1987). The main idea is that, if a given type of damage changes a linear system into a nonlinear system, then any observed manifestation of nonlinearity serves to indicate that damage is present (Farrar et al., 2007). A method of structural damage detection called Local Damage Factor (LDF) was presented by Shanshan et al. (2006), which is capable of determining the presence, severity, and location of structural damage at the same time. This method is based on auto-correlation and crosscorrelation of the entire structure response and local structure response. A study regarding the development of a damage detection indicator for civil engineering structures was performed by Zabel (2005) which is based on energy components of wavelet decompositions of measured signals’ impulse response and transmissibility functions. There has also been some research using wavelet analysis to locate discontinuity caused by damage using local analysis of the signal (Ovanesova and Sua´rez, 2004). In this method, the response needs to be obtained only at the regions where it is suspected that the damage may be present. Wavelet analysis could detect the place of pre-embedded damage in the structure. Recently some research has been conducted to extract damage caused by earthquake loading directly from stories’ seismic responses (Todorovska and Trifunac, 2009; Raufi and Bahar, 2010; Todorovska and Trifunac, 2008; Lynn et al., 1997; Bisht, 2005; Safak and Hudnut, 2006). These responses can be measured by using instruments planted on structures and can be aceleration, velocity or displacement responses. Processing of these recorded signals can reveal some information regarding the time and location of damage. A study on the acceleration responses of a six-storey concrete building in the Southern California area has shown that wavelet analysis of the recorded responses has useful information about the time and location of damage (Todorovska, Trifunac, 2009). On the other hand, different response components do not have the same amount of Raufi and Bahar 2123 information about the formation of plastic hinges, so choosing a specific response which is more sensitive to changes due to nonlinear behaviour of the structure is also an important issue. Research conducted by Raufi and Bahar (2010) demonstrated that nodal rotational response can be a good indicator of plastic hinge location. Wave travel has also been used to determine damage location (Todorovska and Trifunac, 2008). The travel time can be computed having the seismic response in different stories. The main concept of this method is the reduction of wave transferring velocity due to damage. Time Delay (TD) in inter-storey propagation indicates local damage, where TD in wave propagation from the basement to top floor indicates global damage. In this research, the acceleration response of different stories has been selected for processing. It will be shown that by having an impulse response function of a linear structure in the time domain, useful information can be obtained about the time and location of plastic hinges formed in case of a real earthquake. Impulse response function A discrete linear system is a digital implementation of a linear time-invariant system (LTI). Its input is a vector representing the sampled input signal and its output is a vector of the same size as the input, representing the sampled output signal. Any sampled signal is just a series of scaled impulses whose amplitudes are the instantaneous amplitudes of the original analogue signal which occur regularly at the sampling instants. Thus if the input signal (ground acceleration) is just a series of impulses considering that the system obeys the principle of superposition; by knowing the system’s response to impulses, the output (response) of the system to any input signal can be calculated using convolution (Lynn et al., 1997)
