Seismic Response of Plan Regular G+15 RC Structure and Analysis of Structure by ETABS

Abstract

The present study evaluates the seismic performance of a G+15 reinforced concrete (RC) framed building using ETABS software in accordance with IS 1893 (Part 1): 2016. The building is modelled as a plan-regular structure located in Seismic Zone V with medium soil conditions. Modal Analysis, Equivalent Static Analysis, and Response Spectrum Analysis are carried out to assess the dynamic behaviour of the structure under earthquake loading. Important structural parameters such as natural time period, modal participation ratio, base shear, storey displacement, and storey drift are obtained and analysed. The results indicate that seismic response varies significantly along the height of the building, with maximum displacement and drift occurring at the upper storeys while remaining within the codal limits. The study demonstrates that ETABS is an effective tool for evaluating the seismic behaviour of multi-storey RC buildings and provides valuable information for designing safe and earthquake-resistant structures.

Introduction

This study evaluates the seismic performance of a G+15 reinforced concrete (RC) building using ETABS software in accordance with IS 1893 (Part 1): 2016 for Seismic Zone V with medium soil conditions. As rapid urbanization has increased the construction of high-rise buildings in earthquake-prone regions, assessing their seismic safety has become essential to minimize structural damage and ensure occupant safety.

The research performs three standard seismic analyses: Modal Analysis, Equivalent Static Analysis, and Response Spectrum Analysis. These analyses are used to determine important structural parameters such as the fundamental natural time period, modal participation ratio, base shear, storey displacement, and storey drift, providing insight into the dynamic behaviour and earthquake resistance of the building.

The literature review indicates that various lateral load-resisting systems, particularly steel bracing, significantly improve the seismic performance of RC buildings. Previous studies consistently show that X-bracing is more effective than other bracing configurations, such as V-bracing, in reducing lateral displacement and inter-storey drift while increasing structural stiffness.

The objectives of the study are to analyse the seismic behaviour of the G+15 building using ETABS, perform the required analyses according to IS 1893 (Part 1): 2016, evaluate key structural response parameters, and assess the building’s overall seismic performance under earthquake loading.

A three-dimensional ETABS model of the building was developed with RC beams, columns, slabs, and concentric steel bracing. The structure was designed for Seismic Zone V, with a 48 m total height, 5 m bay width, M30 concrete, Fe500 reinforcement, and Fe250 structural steel. Dead load, live load, and earthquake loads acting in both X and Y directions were considered, with the seismic mass calculated from the dead load and 25% of the live load as specified by IS 1893.

The modal analysis identified the building's dynamic characteristics, with a program-calculated fundamental time period of 3.535 seconds, compared to 1.367 seconds estimated by the empirical equation in IS 1893. Higher vibration modes and corresponding frequencies were also determined to understand the building’s dynamic response.

Conclusion

The seismic performance of a G+15 reinforced concrete building was evaluated using ETABS in accordance with IS 1893 (Part 1): 2016. Based on the analytical results, the following conclusions are drawn: 1) Modal Analysis successfully determined the natural time period and modal characteristics of the building, providing an understanding of its dynamic behaviour. 2) Equivalent Static Analysis and Response Spectrum Analysis effectively evaluated the seismic response of the structure under earthquake loading. 3) The maximum base shear obtained was 10850.26 kN in the X-direction and 9765.23 kN in the Y-direction, indicating the seismic forces acting on the structure. 4) The maximum storey displacement occurred at the top storey, with values of 211.616 mm in the X-direction and 190.419 mm in the Y-direction. 5) The maximum storey drift was observed in the middle storeys and remained within the permissible limits specified by IS 1893 (Part 1): 2016, indicating satisfactory seismic performance. 6) The study demonstrates that ETABS is an efficient tool for seismic analysis and that the adopted structural configuration provides adequate stability and safety under seismic loading

References

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Copyright

Copyright © 2026 Moksha C K, Madhukaran . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.