چكيده به لاتين
Earthquake, as one of the most important catastrophic events in the world, still causes major damages to people, governments and societies. Over the past decades, building design codes have improved considerably for the seismic design of buildings, however, there are still some major drawbacks. One of the most important of them is ignoring the effects of aftershocks. Seismic sequence is one of the most important and up-to-date topics in the field of structural design based on the performance level of the structure. The first criterion in most seismic designs is the prevention of human casualties and the prevention of Its collapse. Common systems resistant to seismic load, such as moment-resisting frames or bracing frames, etc., which are designed based on codes, in earthquakes that have occurred during their service life, from the safety view of point, have had a good performance, but the level of damage to the structures, the economic losses caused by the non-use of the structure after the earthquake event, and the cost of repair have been significantly high; Therefore, there is a need for a system that not only meets the safety level of the residents' lives, but also has the ability to be easily repaired at a lower cost. It is necessary to use novel systems that can reduce the effects of earthquakes, which is a natural and undeniable disaster.
In this research, firstly, 3, 6, and 9-story structures, which are representative of short, medium, and high-rise structures, in two type of fixed base and isolated in two special and intermediate moment-resisting frame were designed in 3 dimension by Etabs software in elastic manner. In order to obtain non-linear results and also to investigate the effect of seismic sequence on the structures, the structures were simulated in openseese finite element software in 2 dimensions with the method of plastics hinge element. In order to consider the effect of seismic sequence, first the structures were subjected to incremental dynamic analysis in non-sequence mode by means of 22 FEMA P-695 far-field records and finally by choosing one of the records as the mainshock and the other records As aftershock, the structures in the sequence mode were subjected to increasing dynamic analysis and finally, by developing the fragility curves for the structure, the isolation effects and also the effects of the seismic sequence were investigated. The obtained results show that the isolator in short-story structures is more effective in reducing inter-story drift than in medium and high-rise structures. On the other hand, the increase in the intensity of the mainshock causes an increase in the inter-story residual drift before applying aftershocks and increases the Exceedance probability at different levels of failure. The ratio of IM_ss/IM_ms for 3, 6 and 9 story structures in isolation mode is approximately equal to 87.6, 87.4 and 90% respectively and in fixed-base mode it is approximately equal to 81.9, 79.1 and 79.6% According to the above ratios, The effect of seismic sequence on isolated structures is more than fixed-base structures.
