Volume 13, Issue 1 (2013)                   IQBQ 2013, 13(1): 89-99 | Back to browse issues page

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Karami Mohammadi R, Mohammadi M. Utilizing Earthquake Response Spectrum To Calculate The Floor Acceleration of Steel Frames. IQBQ. 2013; 13 (1) :89-99
URL: http://journals.modares.ac.ir/article-16-5047-en.html
Abstract:   (3153 Views)
The importance of non-structural components in seismic Performance Based Design of buildings is well known nowadays. In this research calculation of absolute acceleration applied on nonstructural components located on floors of moment-resisting, eccentric braced and concentric braced frames subjected to earthquake ground motions has been studied. The results of nonlinear time-history analyses of 3, 5 and 7-story steel frames with 8 different periods and 5 reduction factors subject to 15 records of near-field earthquakes and 15 records of far-field earthquakes has been used to investigate the effects of different parameters on absolute acceleration induced in each floor of the structures. The steel frames have been designed in accordance with ASCE 2005 requirements. The effect of inelastic behavior of system, natural periods of primary and secondary systems, structural system type and near-field ground motions have been studied. To perform expanded parametric studies on various frames with different stiffness and strength, modified shear building models for these frames were constructed. The shear building models are set to have an equivalent lateral force-deformation behavior in each story to the one’s of given steel frames. Reliability of these models to estimate the maximum roof displacement and the maximum inter-story drift of steel frames has been investigated elsewhere through probabilistic analysis of the results obtained from comprehensive incremental dynamic analyses. In this study for each frame 8 period: 1/4, 1/3, 1/2, 2/3, 1, 4/3, 2, 4 seconds are considered. In order to achieve the proper period of shear-building models, keeping the stiffness and strength ratio of stories unchanged, initial stiffness of first story is adjusted proportionally. The relationships that are presented in building codes to calculate the force applied on nonstructural components has been usually expressed as a ratio of peak ground acceleration. This method of calculating of input acceleration to nonstructural elements ignores the effect of frequency content of design ground motion. The results of the present study have been used to introduce a new method for calculation the force applied on nonstructural components based on ground acceleration spectrum. In this method the input acceleration to nonstructural components has been expressed as a ratio of earthquake response spectrum (instead of the peak ground acceleration). For this ratio which is entitled as “spectral amplification factor” two different expressions have been proposed for use in structures with linear and nonlinear behavior. This approach explicitly accounts for the frequency content of design earthquake in calculation of peak floor acceleration. The results of this study show that Euro-code 8 and ASCE 7-2010 recommendations need to modify specially for the precise location of the non-structural element and inelastic behavior of the structure. It has been demonstrated that structural system type does not significantly affect the amount of induced acceleration on each floor of steel frames.
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Article Type: Original Manuscript | Subject: omran
Received: 2012/03/5 | Accepted: 2013/03/21 | Published: 2013/06/23

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