Review Paper on Comparative Study and Analysis of Vertical Mass Irregularities of RCC Building with Zone 3 and Zone 5

Abstract

The rapid pace of urbanization has led to the widespread construction of RCC building in seismically active zones. Many of these structures, however, where designed according to outdated codes that did not fully account for increased population density are the potential for strong earthquakes. The vulnerability of these building is often linked to mass irregularities, which disrupt the uniform distribution of weight across floor, resulting in poor structural performance during seismic events. This paper focus on studying the impact of mass equality at different floor level and different seismic zones in RCC building. Through seismic analysis using methods like the equivalent and response spectrum approach in Etabs, the paper highlights how mass distribution variations influence the structural response, offering insights into safer and more resilient design strategies.

Introduction

Overview

Mass irregularities—sudden variations in floor mass—negatively affect a building’s seismic performance. In multi-story buildings, these irregularities lead to increased vulnerability during earthquakes, causing uneven force distribution, excessive story displacement, drift, and base shear.

With India updating its seismic zoning map, there is now a critical need for both existing and new buildings to conform to modern earthquake-resistant standards.

Objective

The paper investigates how mass irregularity at different floor levels and seismic zones affects the seismic behavior of G+9 RCC buildings, using key parameters such as:

• Base shear

• Story displacement

• Story drift

The goal is to emphasize the importance of proper mass distribution and ductility for structural resilience.

Types of Irregularities

• Plan (Horizontal) Irregularities: Caused by non-uniform building layouts.

  • Examples: Torsional irregularity, re-entrant corners, diaphragm discontinuity, non-parallel systems.

• Vertical Irregularities: Arise from inconsistencies in mass, strength, or stiffness between floors.

  • Includes: Soft storey, weak storey, vertical geometric irregularity, and in-plane discontinuities.

• Mass Irregularity: Defined as a sudden mass increase (150%–200%) at a floor level, making the structure more prone to earthquake damage.

Methodology

The study is based on:

• Comparative studies using Response Spectrum Analysis (RSA) and Time History (TH) Analysis.

• Examination of how vertical mass irregularities affect RCC building performance under seismic loads.

Key Literature Findings

• Swapnil & Basavalingapp (2015): Composite buildings handle mass irregularities better than pure RCC structures.

• Anvesh et al. (2015): Mass-irregular buildings show greater base shear but slightly lower displacement.

• Vijayan & Prakash (2016): Mass irregularities at different levels impact frequency and drift; best to avoid or localize them strategically.

• Mya Aye & Narasimhara (2017): Dynamic analysis shows larger column sizes needed for irregular structures than static analysis.

• Rashmi Patil (2017): Change in irregularity location significantly alters base shear and displacement.

• Hiwase et al. (2021): Mass irregularity causes slightly higher moments than regular structures.

• Sabbir Hossain & Singh (2022): Taller buildings show increased displacement but reduced drift.

• Nilesh Kumar et al. (2022): Maximum drift found under time history analysis; Zone III analyzed with both static and dynamic methods.

• Syed Hussain & Gajendra H. (2023): Compared regular vs irregular multi-storey RCC frames; irregular buildings had higher displacement and base shear.

Conclusion

Many researchers have conducted analytical and comparative studies on the design of high-rise buildings. Although modern codes may recommend strengthening buildings in response to zone upgrades and mass irregularity, it remains essential to verify the adequacy of the existing reinforcement. Regular building exhibit better seismic performance, so for future seismic event and when building seismic zone change. When seismic zone increase than results are more increase to lower seismic zone. Dynamic analysis methods, such as Response Spectrum and Time History analysis, offer more precise results compared to static linear analysis (Equivalent Static Method), particularly for high-rise and irregularly shaped buildings. Among these, Time History analysis is considered the most accurate, as it simulates the actual response of a structure to an earthquake over time. However, it is also more computationally demanding and less cost-effective than Response Spectrum analysis. Response Spectrum analysis strikes a balance between accuracy and efficiency, making it a suitable and widely used method for low- to mid-rise buildings. It is also commonly applied to assess the seismic behaviour of a building both before and after modifications or extensions.

References

[1] Hiwase Dr. Prashant, Taywade Vipul V., Siddh Sharda P. (2021) “Comparative analysis of vertical irregularities on high rise structure considering various parameters”, International Conference on Advances in Civil Engineering (ICACE) 2021. [2] Hossain Md. Sabbir & Singh S.K. (2022) “Comparative Analysis of Irregular RCC Building in Different Zones”,ICASF 2022. [3] Hussain Syed Aatif & H.Gajendra (2023) “Nonlinear Time History Analysis Of Mass And Geometric Regular And Irregular Multi Storey Moment Resisting RCC Frames”, JOURNAL OF SCIENTIFIC RESEARCH AND TECHNOLOGY (JSRT) 2023. [4] Kumar Nilesh, Parmar Jay , Dalal Maitri, Samal Abhishek, Patel Jenish , Patil Y. D. (2022) “Effect of Vertical and Mass Irregularity on RCC Structure Subjected to Seismic Loading”, ASPS 2022. [5] Mya Mya Aye & Narasimhara P. (2017) “Seismic Analysis of Multistoried RCC Building due to Mass Irregularity by Time History Analysis”, Journal of Emerging Technologies and Innovative Research (JETIR) 2017. [6] N.Anvesh , Yajdani Dr. Shaik , K. Pavan kumar (2015) “Effect of Mass Irregularity on Reinforced Concrete Structure Using Etabs”, International Journal of Innovative Research in Science, Engineering and Technology 2015. [7] Patil Rashmi S. (2017) “SEISMIC ANALYSIS OF MULTISTORIED BUILDING WITH AND WITHOUT VERTICAL MASS IRREGULARITY”, International Journal of Research Publications in Engineering and Technology [IJRPET] 2017. [8] Swapnil B & Basavalingapp (2015) “Evaluate Comparative Analysis on the Seismic Behaviour of Combine RC-Masonary”, International Research Journal of Engineering and Technology 2015. [9] Vijayan Asha & Aswathy Prakash (2016) “Study on Seismic Analysis of Multi Storied Reinforced Concrete Building with Mass Irregularities” International Journal of Science and Research (IJSR) 2016.

Copyright

Copyright © 2025 Vinod Kumar Prajapati, 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.