Abstract
Historical seismic damage data show that most strong earthquakes are accompanied by multiple intense aftershocks. In general, the time interval between the main shock and the aftershocks is relatively short, and structure repair work is often not completed before the aftershocks occur. For a structure that has suffered damage from the main shock, the aftershock will further aggravate the damage and even cause complete collapse. Based on the incremental dynamic analysis (IDA) method, this paper establishes a probabilistic seismic demand model for the SRC framework-core tube structure and plots the vulnerability curve of a structure under the action of the main aftershock sequence, which occurs following the actions of frequent earthquakes, fortification earthquakes, and rare earthquakes. The structure vulnerability matrix and the vulnerability index are used to evaluate the seismic performance of a structure. This study found that the occurrence of aftershocks leads the structure to a more unfavourable failure state. Taking the vulnerability index as an evaluation parameter, the structural vulnerability index when subjected to an intensity 8 earthquake under the action of the main aftershock is approximately 10% larger than under the action of a single main shock. Meanwhile, the SRC frame-core structure designed according to the current Chinese specifications meets the expected seismic fortification target, even after being acted upon by the main aftershock ground motion sequence.
Highlights
Historical seismic damage data show that most strong earthquakes are accompanied by multiple large intensity aftershocks
In the elastic time-history analysis, the shear force at the bottom of the structure calculated by each ground motion record should not be less than 65% of that calculated by the mode decomposition response spectrum method. e average value of the shear force at the bottom of the structure calculated from multiple ground motion records should not be less than 80% of that calculated by the mode decomposition response spectrum method. e 15 ground motion records selected for time-history analysis are shown in Table 4, where TA is the predominant period of the aftershock and TM is the predominant period of the main shock
When the ground motion intensity is Sa(T1, 5%) < 1.5 g, the structural vulnerability index of the main aftershock sequence ground motion is higher than the single main shock by 3∼15%
Summary
Historical seismic damage data show that most strong earthquakes are accompanied by multiple large intensity aftershocks. Li and Ellingwood [17] studied the effects of various construction methods of main aftershock sequence ground motion on the vulnerability of steel frame structures. Erefore, it is necessary to make a clear damage assessment by vulnerability analysis of the SRC frame-core tube structure under the main aftershock of the ground motion sequence. En, the IDA method is used to establish the probabilistic seismic demand model, and the vulnerability of the SRC frame-core tube structure under the main aftershock sequence ground motion is studied. According to the seismic damage index given in the specification [30], the damage status of the SRC framecore tube structure is evaluated under the main aftershock of the ground motion sequence
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