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Gdańsk University of Technology

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Development of fragility curves in adjacent steel moment-resisting frames considering pounding effects through improved wavelet-based refined damage-sensitive feature

Fragility curves present useful information related to earthquake-induced probability assessment ‎of steel moment-resisting frames (MRFs) and determine the probability of the damage ‎exceedance at different floor levels of MRFs. The review of the literature shows that most of the ‎previous studies dealing with the fragility curves were based on conventional measures, such as ‎spectral acceleration at the first mode period, peak ground acceleration, and/or engineering ‎demand parameters (e.g. maximum story drift ratio (max SDR)) to estimate the structure's ‎damage state. In this article, a new approach is developed to map the fragility curves in adjacent ‎MRFs including effects of pounding through improved wavelet-based refined damage-sensitive ‎feature (WB-rDSF) which considers contributions of the upper modes. Morlet and complex ‎Morlet (cmorfb-fc) wavelets, which is known as extremely precise rDSF, were extended to map ‎the fragility curves. The correlation coefficient between rDSF and max SDR is evaluated as a ‎criterion to determine the efficiency of wavelets-based damage index (WB-DI). The steel MRFs ‎with six and nine stories are selected to implement the proposed approach concerning adjacent ‎MRFs prone to structural pounding during earthquakes. Acceleration responses recorded at the ‎roof of both colliding and non-colliding MRFs were determined using incremental dynamic ‎analysis (IDA) including different seismic ground motion records to formulate the damage index. ‎Moreover, the first mode structural period, used in assembling the WB-rDSF, is estimated via ‎auto-regressive moving-average with exogenous input method along with a stabilization diagram. ‎The results show that the fragility curves, derived from cmorfb-fc WB-rDSF for both colliding ‎and non-colliding MRFs due to higher correlation coefficient, have lower damage probabilities ‎and are more efficient than the estimated fragility curves based on Morlet WB-rDSF which ‎consider only the structural period of the first mode. Furthermore, due to the pounding ‎phenomenon, the lower MRF experiences more damages with a larger probability.‎

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