Comparative Study on Static and Dynamic Analysis of a G+5 RCC Building as per IS 1893 (Part 1): 2016 on Force Distribution Criteria

Abstract

Earthquake-resistant design requires accurate estimation of seismic forces and structural response. IS 1893 (Part 1):2016 permits both Equivalent Static Analysis (ESA) and Response Spectrum Analysis (RSA) for regular medium-rise buildings; however, their predicted responses often differ significantly. This study presents a comparative seismic analysis of a G+5 reinforced concrete (RCC) building located in Seismic Zone III with medium soil conditions and 5% damping. The building is modelled and analysed using ETABS software following IS 1893 provisions. Force distribution due to static and dynamic analysis are evaluated in both X and Y directions. The equivalent static base shear is found to be higher than the unscaled dynamic base shear; therefore, response spectrum results are scaled to match static base shear as per code requirements. Numerical results indicate that static analysis equivalent static method produces conservative estimates of forces, while response spectrum analysis provides a more realistic distribution of seismic demand along the height. The study concludes that although both methods are applicable for G+5 buildings, dynamic analysis is preferred for reliable seismic performance evaluation.

Introduction

Earthquake-induced lateral forces play a critical role in the seismic performance of RCC frame buildings, which form a major part of urban infrastructure in India. This study compares the Equivalent Static Method (ESM) and the Response Spectrum Method (RSM), as prescribed by IS 1893 (Part 1): 2016, to evaluate their effectiveness for a medium-rise G+5 RCC building.

The objective is to analyze and compare both methods in terms of base shear, storey shear distribution, and member forces in the X and Y directions, and to assess the impact of base shear scaling on dynamic analysis results. The scope is limited to a regular, linear elastic RCC moment-resisting frame modeled in ETABS, considering Zone III seismicity and medium soil conditions.

A three-dimensional building model with identical geometry, material properties, mass distribution, and loading was analyzed using both approaches. In ESM, seismic base shear was calculated using codal parameters and distributed linearly along the height. In RSM, modal analysis was carried out using the design response spectrum, with modal responses combined by the SRSS method. As required by the code, dynamic base shear was scaled to match the static base shear.

Results show that unscaled dynamic base shear is significantly lower than static base shear due to modal participation effects. After scaling, both methods yield the same total base shear. However, storey shear distribution differs: ESM produces higher shear at upper storeys, while RSM concentrates shear more realistically towards lower storeys. Similarly, beam bending moments from ESM are consistently higher, indicating its conservative nature, whereas RSM provides smoother and more realistic force distribution. Column axial forces show less variation between the two methods.

Conclusion

From the present study, the following conclusions are drawn: 1) The base shear obtained from response spectrum analysis was lower than that from the equivalent static method because dynamic analysis distributes seismic inertia forces among multiple vibration modes rather than assuming dominance of the fundamental mode. As a result, the cumulative modal response leads to reduced base shear, which was subsequently scaled to match the equivalent static base shear as required by IS 1893. 2) Beam bending moments (BM) obtained from the equivalent static method were higher than those from the response spectrum method, indicating conservative estimation of flexural demand. 3) Column axial forces showed comparatively smaller variation between static and dynamic analyses, with response spectrum analysis capturing a more rational redistribution of axial forces along the building height. 4) Overall, response spectrum analysis provides a more accurate representation of seismic demand and is preferable for detailed seismic assessment of G+5 RCC buildings.

References

[1] Agarwal P. and Shrikhande M., Earthquake Resistant Design of Structures, New Delhi, India: PHI Learning Private Limited, 2011. [2] American Concrete Institute, Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19), Farmington Hills, MI, USA: American Concrete Institute, 2019. [3] Bagheri B., Firoozabad E. Salimi and Yahyaei M., “Comparative study of the static and dynamic analysis of multi-storey irregular buildings,” International Journal of Civil and Structural Engineering, vol. 6, no. 11, pp. 1045–1049, 2012. [4] Bajpai Shobit, Grover R.K “Earthquake Resistance Performance of a Multistorey RCC Frame Considering Two Different Positions of the Staircase.” International Journal for Research in applied science and Engineering Technology, Volume 10, Issue ?, Sep 2022. [5] Bureau of Indian Standards, IS 875 (Part 1): 1987 – Code of Practice for Design Loads (Other Than Earthquake) for Buildings and Structures: Dead Loads, New Delhi, India. [6] Bureau of Indian Standards, IS 875 (Part 2): 1987 – Code of Practice for Design Loads (Other Than Earthquake) for Buildings and Structures: Imposed Loads, New Delhi, India. [7] Bureau of Indian Standards, IS 1893 (Part 1): 2016 – Criteria for Earthquake Resistant Design of Structures: General Provisions and Buildings, New Delhi, India. [8] Bureau of Indian Standards, SP 16: 1980 – Design Aids for Reinforced Concrete to IS 456, New Delhi, India. [9] Duggal S.K., Earthquake-Resistant Design of Structures, 2nd ed., New Delhi, India: Oxford University Press, 2013. [10] Gottala A. and Kishore N.S., “Comparative study of static and dynamic seismic analysis of a multistoried building,” International Journal of Science, Technology & Engineering, vol. 2, no. 1, pp. 173–180, 2015. [11] Khan Mohammed Mohiuddin, Khan Mohammed Furqan Ali, Karimuddin Khaja and Charan K. Sai, “Comparative Study of Linear Static and Linear Dynamic Method of Seismic Analysis of RCC Multistoried Building Using ETABS.” International Journal for Research in Applied Science & Engineering Technology, Volume 10, Issue V, May 2022 [12] Mahmoud S. and Abdallah W., “Response analysis of multi-storey RC buildings under equivalent static and dynamic loads according to Egyptian code,” International Journal of Civil and Structural Engineering Research, vol. 2, no. 1, pp. 79–88, 2014. [13] Masatkar Varsha, Grover R.K “Comparison of Low-Rise Open Ground Storey Framed Building in Different Earthquake Zones.”International Research Journal of Education and Technology, Volume: 04, Issue: 04, April 2022. [14] Meleka N., Hekal G., and Rizk A., “Comparative study on static and dynamic analysis of structures,” Engineering Research Journal, vol. 39, no. 4, pp. 277–283, 2016. [15] Singh Rohan, Grover R.K “Comparative Study and Analysis of Conventional and Diagrid Building in Seismic Loading.”Journal of Computational Analysis and Applications (Scopus indexing), Volume 33, No. 8, 2024.

Copyright

Copyright © 2026 Rahul Meena, R. K. Grover. 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.