The main objective of the present study is to investigate that, in view of estimating the seismic performance of the structures as well as reducing the computational time in incremental dynamic analysis, whether the extracted pulses from the near-fault ground motions well represent the original records or not?ī) Constituent sinusoides of different frequencies In 2012, another approach was presented based on mixing the concepts related to absorbed energy by the structure in the time of earthquake and wavelet analysis in order to calculate the velocity pulse period. (2010) made use of consecutive average based on fast Fourier transform in order to divide 91 records identified as pulse ones by Baker and used two factors including pulse type record having low frequency and background record along with high frequency. The main objective of the study was to apply the concept of “the probability of pulse occurrence” in risk analysis studies. In 2007, Baker utilized wavelet transform analysis to obtain the velocity pulses and identified the pulse-type records in NGA seismic database. On the other hand, some scholars used non-stationary signal processing methods in order to extract the pulses of near-fault records. As a result, numerous mathematical models have been proposed to meet this goal.
Although numerous researchers have acknowledged the velocity record as an appropriate indicator to explain the nature of the near-fault records, they attempted to present several models for estimating this pulse-type part of the record and evaluating the relevant parameters to the structural responses under such records. On the other hand, the reported records of the near-fault ground motions show that a large amount of energy of these records are expressed cumulatively and in the form of a pulse-type factor in the velocity record of these ground motions. This is computationally both time-consuming and costly. Hence, using this method, the records should be scaled from a very low intensity measure (IM) to a very high one. The IDA entails conducting non-linear analysis on the structural model under a set of earthquake records scaled in several intensity levels and imposed to the structure so that it undergoes from a linear elastic stage to non-linear complete collapse stage. The incremental dynamic analysis (IDA) is an appropriate and precise method for probabilistic evaluation of the collapse of the structures. The collapse prevention of the structures is one of the most important threshold levels to evaluate the performance of the structures under the seismic excitations. Keywords: near-fault ground motions, extracted pulse, collapse intensity measure, collapse fragility curve, collapse capacity median, special moment resisting frame (SMRF). Nevertheless, if the structure is designed for collapse prevention (CP) performance level and experiences high level of non-elastic displacements, the extracted pulses provide a conservative estimation of the collapse capacity, which is in the safe side. From the numerical analysis performed in the present study, it is found that if a given structure is designed for immediate occupancy (IO) performance level (low drift), the application of the extracted pulses overestimates the structure capacity, which is in the unsafe side. The results of this study revealed that the efficiency of the extracted pulses to estimate the structure capacity depends on the structural performance levels. Subsequently, an incremental non-linear dynamic analysis (IDA) was conducted to evaluate the non-elastic response of an example frame subjected to these original records and their extracted pulses to examine the efficiency of the extracted pulse of the records instead of the original accelerograms in dynamic analysis. In the present study, by using a wavelet analysis, the long period pulses exist in the velocity records of 28 near-fault ground motions, selected from the PEER NGA database, were first separated from the original records. Killer Sound FX! Built for Motion Design.Earthquake accelerograms recorded in the near-fault regions have special characteristics including the long-period pulse in velocity records as well as high frequency content in acceleration records.
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