Seismic Analysis and Design of Vertically Irregular Mutistoried RC Concrete Building using Staad Pro V8i
This paper is concerned with the effects of a variety of vertical irregularities on the seismic response of a structure. The objective of the project is to carry out Response spectrum analysis RSA and Time history Analysis THA of vertically irregular RC building frames and to carry out the ductility based design using IS 13920 corresponding to Equivalent static study and Time history analysis. Comparison of the results of analysis and design of irregular structures with regular structure was done. The scope of the project also includes the evaluation of response of structures subjected to high, low and intermediate frequency content earthquakes using Time history analysis. Three types of irregularities namely mass irregularity, stiffness irregularity and vertical geometry irregularity were measured. According to our examination the storey shear force was found to be maximum for the first storey and it decreases to minimum in the peak storey in all cases. The mass irregular structures were observed to occurrence larger base shear than similar regular structures. The stiffness irregular structure experienced lesser base shear and has larger inter storey drifts. The total displacements obtained from time history analysis of geometry irregular structure at respective nodes were found to be larger than that in case of regular structure for high stories but steadily as we moved to lower stories displacements in both structures tended to congregate. Lower stiffness results in higher displacements of upper stories. In case of a mass irregular structure, time history analysis gives a little higher displacement for upper stories than that in regular structures whereas as we move down lower stories show higher displacements as compared to that in regular structures. When time history analysis was done for regular as well as stiffness irregular structure, it was found that displacements of upper stories did not vary much from each other but as we moved down to lower stories the total displacement in case of soft storey were higher compared to respective stories in regular structure. High structures were found to have low natural frequency hence their response was found to be maximum in a low frequency earthquake. It is because low natural frequency of tall structures subjected to low frequency earthquake leads to resonance resulting in larger displacements. If a high rise structure low natural frequency is subjected to high frequency ground motion then it results in small displacements. Similarly, if a low rise structure high natural frequency is subjected to high frequency ground motion it results in larger displacements whereas small displacements arise when the high rise structure is subjected to low frequency ground motion.
by Anjali Raw | Ashish Verma “Seismic Analysis and Design of Vertically Irregular Mutistoried RC Concrete Building using Staad Pro V8i”
Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-1 , December 2019,
Seismic Analysis and Design of Vertically Irregular Mutistoried RC Concrete Building using Staad Pro V8i IEEE PAPER
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