The Effect of Earthquake Vertical Component on Structures with Mass and Stiffness Irregularities in Height
Subject Areas : Analysis of Structure and EarthquakeMasoud Jahanpanah 1 , Hossein Sohrabzadeh 2
1 - Department of Civil Engineering, Semnan University
2 - Department of Civil and Environmental Engineering, Tarbiat Modares University
Keywords: structures, earthquake vertical component, mass and stiffness irregularities height,
Abstract :
The earthquake vertical component and its influence on the analysis of buildings have long been considered by researchers and design engineers. However, so far, the considerations resulting from the effect of the vertical component of the earthquake in the design of buildings (unless partially in beams) with irregular mass and stiffness in height have not been studied. For this reason, this research is important in order to answer the question regarding impact of earthquake vertical component on buildings, which have irregularity in mass and stiffness in the height. So far, most of the research about the buildings with mass and hardness irregularities in the height has been studied only with respect to the influence of earthquake with horizontal component. However, the 2800 standard does not comprehensively predict the effect of the vertical seismic component on seismic loading, and the only effect of the vertical seismic component according to the 2800 standard is significant for the earthquake prone areas, cantilever beams, beams with a span of more than fifteen meters and beams with remarkable concentrated vertical load. According to the above cases to investigate the influence of seismic vertical component in the buildings with mass and hardness irregularity in the height, three 10-floor structures with steel curving frames, each in a different form on sixth floor, with mass and hardness irregularity, were analyzed. This irregularity is observed in standard 2800 boundary. The structures are then subjected to nonlinear dynamic analysis under five earthquake groups with PGA (Earth Acceleration Peak) values of 0.2g, 0.35g, 0.5g, 0.65g and 0.8g. It should be noted that each group has seven earthquakes that have three accelerometers (two horizontal components and one vertical component). Then, the maximum results of each earthquake are obtained and these results are averaged for each separate group and the obtained result is considered as the final result. The results of nonlinear dynamic analysis presented that through the interference of the vertical seismic component, the amount of drift ratio in the floor containing mass and stiffness irregularity, increased by about 5 to 25 percent and the amount of axial force of the column increased by about 5 to 30 percent.
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