International Research Journal of Engineering and Technology (IRJET) Volume: 04 Issue: 03 | Mar -2017
www.irjet.net
e-ISSN: 2395 -0056 p-ISSN: 2395-0072
Study on Seismic Behaviour of Tall Irregular Buildings under Influence of Non Parallel and Offset Irregularities Lohith Kumar B C 1 1,2Asst.Professors
Manjunath N K 2
Gangadhar N 3
Department of Civil Engineering Madawalabu University Bale Robe Ethiopia
3Asst.Professor
Department of Civil Engineering RRCE Bangalore India
--------------------------------------------------------------------------------------------------------------------------------------------------Abstract -The present study aims at understanding the importance of codal provisions, which are particularly provided for the analysis of torsionally unbalanced structures. IS 1893-2002 Part 1 Code gives the information about number of parameters which influences the irregularity of the structure. However, in the present study the worst affected irregularity under the influence of torsion are studied, In the present study, seismic analysis has been performed by Equivalent Lateral Force Method (ELF) ie the codal method, for all zones and for all soil types irregularities such as Non parallel irregularity and Offset irregularity for 10, 15, 20 storey buildings
Hence, the following objectives were identified based on these parameters. The present study focuses on the discontinuities in a lateral force resistance path, such as out-of-plane offsets of vertical elements etc. 1. 2.
The results in form of torsional moment, fundamental time period and base shear results are compared for different irregularities and the analysis is done with Etabs 9.2 software.
REVIEW OF LITERATURE Anil K. Chopra et.al (2004) [2] study compares the seismic demands for vertically irregular and ‘‘regular’’ fram9es determined by rigorous nonlinear response history analysis (RHA), due to an ensemble of 20 ground motions. Forty-eight irregular frames, all 12-story high with strong columns and weak beams, were designed with three types of irregularities stiffness, strength, and combined stiffness and strength introduced in eight different locations along the height using two modification factors. The effects of vertical irregularity on the median values of story drifts and floor displacements are documented. Next, the median and dispersion values of the ratio of story drift demands determined by modal pushover analysis (MPA) and nonlinear RHA were computed to measure the bias and dispersion of (MPA) estimates leading to the following results: (1) the bias in the MPA procedure does not increase, i.e., its accuracy does not deteriorate, in spite of irregularity in stiffness, strength, or stiffness and strength provided the irregularity is in the middle or upper story, (2) the MPA procedure is less accurate relative to the regular frame in estimating the seismic demands of frames with strong or stiff-and-strong first story; soft, weak, or soft-and-weak lower half; stiff, strong, or stiff-and-strong lower half, (3) in spite of the larger bias in estimating drift demands for some of the stories in particular cases, the MPA procedure
STATEMENT OF THE PROBLEM Seismic induced torsion in asymmetric RC buildings has been studied for various parameters. Equivalent Lateral Force Method (ELF) adopted to study the induced torsion as per IS 1893(Part 1): 2002 codal provisions. ETABS v9.5.software package is used to carry all the static and dynamic analysis. Since the present study is devoted for the investigation of torsional behaviour of asymmetric structures, in order to capture exact three dimensional behaviour, all the analysis are performed on complete three dimensional models of the structures. OBJECTIVES OF THE STUDY The present study aims at understanding the importance of codal provisions, which are particularly provided for the analysis of torsionally unbalanced structures. IS Code gives the information about number of parameters which influences the irregularity of the structure. However, in the present study the irregularity under the influence of torsion are studied in detail.
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To study the influence of discontinuities in a lateral force resistance path, such as out-of-plane offsets of vertical elements etc. To study the influence of Non parallel System ie the vertical elements resisting the lateral force which are not parallel about major orthogonal axes.
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