Study of Structural Parameters Effect Caused by Soft Storey in Multi-Storey Building

Abstract

In the present work study is carried out for the behavior of G + 10 storied RC buildings with Rectangular shaped plan of soft storey at different levels. Floor height provided as 3.4m and also properties are defined for the irregular R.C building modelled in STAAD. Pro V8i software. Here twelve models are created in which soft storey is provided at ground, fifth and eleventh storey in all four seismic zones. From result it is found that Location of Soft storey effects seismic behavior of building in every zone from low to high seismicity. As the location of soft storey goes upper it gives more stable structure compared to soft storey at ground level. Soft storey at top level of structure is more stable than soft storey at middle part of structure, soft storey at top level gives Lower values of displacement in all seismic zones.

Introduction

The study focuses on the seismic behavior of multi-storey buildings with soft storeys—floors intentionally designed with reduced stiffness or strength, often for functional needs like parking or commercial use. Such soft storeys are critical because they tend to cause structural vulnerability during earthquakes, primarily due to increased lateral displacement and storey drift.

Building codes address irregularities like soft storeys mainly via stiffness contrasts between floors, but displacement-based criteria are considered more effective. The literature review highlights various research studies on seismic response of buildings with vertical irregularities—mass, stiffness, and soft storeys—using methods like Response Spectrum Analysis (RSA) and static analysis.

Key findings across multiple studies include:

• Irregular buildings, especially those with soft or weak storeys, generally perform worse under seismic loads than regular, symmetrical buildings.

• Mass irregularity often increases base shear forces, while stiffness irregularity can lead to higher inter-storey drifts.

• Soft storeys exhibit maximum displacement and storey drift at their level, causing potential failure points.

• Adding elements like shear walls or infill walls improves stability and reduces displacement.

• Dynamic (response spectrum or time-history) analyses provide better performance predictions than static methods.

The study’s methodology involves modeling a G+10 reinforced concrete building with soft storeys at different levels across four seismic zones using STAAD.Pro software. Material properties, load combinations (gravity, seismic), and building parameters (dimensions, loads, damping) follow Indian standards (IS codes). Equivalent static seismic analysis was conducted to evaluate axial forces, bending moments, storey drift, and displacements.

Results show variations in axial force, moment, and displacement depending on the soft storey location and seismic zone, confirming the adverse impact of soft storeys on building seismic performance.

Conclusion

1) Soft storey at top level gives Lower values of displacement in all seismic zones 2) soft storey at upper floor level gives gives lowest values of Axial forces and bending moment in low and moderate seismic zone, while gives a slight higher values of moments in severe and very severe seismic zones compared to soft storey located at middle floor level

References

[1] bInfluence Of Mass Irregularity On The Seismic Design And Performance Of Multi-Storey Braced Steel Frames 13th World Conference on Earthquake Engineering Vancouver, B.C., Canada August 1-6, 2004 Paper No. 2896 Poncet, L.1 and Tremblay, R.2 [2] Seismic analysis of multistoried rce building due to mass irregularity©2016 IJEDR | Volume 4, Issue 3 ISSN: 2321-9939IMr. Pathan Irfan Khan, 2Dr.Mrs. N.R.Dhamg [3] Seismic Analysis And Design Of Vertically Irregular R.C. Building FramesInternational Journal of Advance Research in Science and Engineering Volume No.07 Special Issue No. 04, April 2018Shridhar Chandrakant Dubulel, Darshana Ainchwar2 [4] Response of Building Frames with Vertical and Stiffness Irregularity due to Lateral LoadsInternational Journal of Engineering Research & Technology (IJERT) Vol. 2 Issue 12, December 2013Abul Hasnat M Rifat Ibtesham Rahim [5] Seismic Analysis of Multistoried RCC Building due to Mass Irregularity by Time History AnalysisDecember 2017, Volume 4, Issue 12 JETIR (ISSN-2349-5162)1Mya Mya Aye, 2P.Narasimharao [6] Effect of Soft Storey on Tall Building At Different Floor LevelsInternational Journal of Innovative Research in Science, Engineering and Technology (An ISO 3297: 2007 Certified Organization) Vol. 5, Issue 8, August 2016Mohamed Riyas N.K1, Dr.RaneeshK. Y2, MarshiyathK.P3 [7] Seismic Analysis of Multi-Storey Irregular Building with Different Structural SystemsInternational Journal of Recent Technology and Engineering (IJRTE) ISSN: 2277- 3878, Volume-8 Issue-6, March 2020Vishal N, Ramesh Kannan M, Keerthika L [8] Dynamic Seismic Evaluation of Irregular Multi-Storey Buildings Using Bracing in Zone V as Per Is: 1893-2016 [9] International Journal of Innovative Technology and Exploring Engineering (IUITEE) ISSN: 2278-3075, Volume-8 Issue-7, May, 2019 Lovneesh Sharma, Sandeep Nasier [10] Analysis Of Soft Storey Effect At Different Levels In A framed Structure With And Without Shear Wall For Different Seismic ZoneInternational Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395- 0056 Volume: 05 Issue: 08 | Aug 2018 www.irjet.net p-ISSN: 2395-007Sanjay G KI, Dr. B Shivakumara swamy2 [11] Seismic Response of Irregular RC Building with Soft Storey at Different Levels International Journal of Science and Research (USR) ISSN (Online): 2319-7064 Index Copernicus Value (2013): 6.14 (Impact Factor (2015): 6.391Silpa Rani M V1, Aiswarya S2

Copyright

Copyright © 2025 Sanket P Sharma, Prof. R. M. Phuke. 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.