• Mohammad Nazari
  • Aliraza Nikbakht Shahbazi



Abstract. The behavior of structures at the time of the occurrence of large earthquakes enters the
nonresponsive range, and their design requires a nonresponsive analysis, but due to the costly nature of this method and its effect to enhance the effect of nonresponsive behavior and energy dissipation due to hysteresis behavior, The damping and the effect of the excessive strength of the structure transform this reactionary force by the coefficient of reduction of resistance or the coefficient of behavior into the design force. Determining the magnitudes of these coefficients in earthquake regulations is mainly based on performance observations of building systems in past earthquakes and based on engineering judgments. One of the cases that has a significant effect on the behavior of structures is irregularity in height, which according to researchers many expressed their concern about the lack of reasonable behavioral coefficients based on research studies and computational backing and emphasized on the
correction of these coefficients based on scientific studies. In this study, using finite element software, irregular effects in the defense is studied on the coefficient of behavior of concrete structures studied is. In the present study, 30 flexural concrete frames have been studied regularly and irregularly in structures with 3, 6, 9, 12, 15 floors in elevations with different openings of 4, 6 and 8 meters. The structures were selected for elastic analysis in order to design, model, and load. After this stage, the structures were modeled for non-elastic analysis (nonlinear static analysis with increasing lateral loading) and then the coefficient of structure behavior was calculated. According to the results, in most cases, the coefficient of reduction due to ductility (R μ ) in regular concrete structures at altitude is
more than that of irregular structures, in other words, in structures with the same number of floors and openings, concrete structures regularly, they have better fitting height than irregular structures at elevation. In particular, it can be said that the coefficient of reduction due to irregular structure (Rμ) in irregular structures at elevation is 91% of its value in the structure regularly in height, in this study, with increasing the number of floors from 3 to 6, the resistance coefficient is decreasing further, but from 6 floors to then, in structures 9, 12 and 15, there is no significant change in the resistivity coefficient. Also, the regular or irregularity of the structure did not make any difference in the change in the value of this coefficient. The overall behavior of the structure (R) also affects the
regular concrete structures at altitude there is a greater amount than the irregular structures at elevation. The regular structures with the number of floors and the size of the span have a higher coefficient of behavior than the irregular structures at elevation. The results showed that the coefficient of behavior obtained from nonlinear dynamic analysis the linear average is about 15% higher than the values obtained by nonlinear static analysis with making side are increasing and there is little difference between the two methods.
Keywords: Structural behavior coefficient -irregularity at height-concrete structures.


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