Push Over Analysis of RCC Building with Soft Stories at Different Levels

Abstract

The increase in population, parking spaces is a major problem for the apartments of the cities. Hence fresh trend is making use of the open ground storey for parking. Also, for office, shop spaces, or conference hall etc., soft story at different levels of structure is construction. In the beyond (past) earthquake has shown that the buildings with simple (unsophisticated) and uniform configurations are subjected to less damage. The regularity and continuity of stiffness in the horizontal planes as well as in vertical direction is very important from earthquake safety point of view. A building with discontinuity is subjected to concentrated of forces and deformations at dot of the discontinuity which may leads to the failure of members at the junction and collapse of building. Open first storey is a typical feature in the modern multi-storey constructions in metro city India. Such as the features highly unacceptable of the buildings built in seismically active areas; as a been verified of numerous experiences the strong shaking during the past earthquakes. It is the thought of multi-storey buildings with soft ground floor are inherently vulnerable to breakdown due to earthquake load, their construction is still widespread in the developing nations like India. It is the social and functional demand to provide car parking space at ground level and for offices open stories at other level of structure away out-weighs the warning against such buildings from engineering community. The ground soft story for office space open floor is required on other levels of building. In present work we are concentrating on finding the best place for soft stories in high rise buildings.

Introduction

The rapid rise of tall and slender buildings has made lateral loads—such as earthquakes, wind, and blast forces—a central concern in structural design. Unlike traditional approaches focusing on vertical loads, modern engineering emphasizes seismic safety, serviceability, and economic considerations. Earthquakes induce large inelastic deformations, and controlled structural damage is often allowed to dissipate energy without collapse. Past seismic events, such as the 2001 Kutch earthquake, highlight the consequences of inadequate earthquake-resistant construction, emphasizing the need for strength, ductility, and structural integrity. Performance-based seismic engineering and methods like pushover analysis enable designers to predict structural response and achieve objectives like Immediate Occupancy, Life Safety, or Collapse Prevention.

Methodology

• Six RCC building models (G+1, G+3, G+5, G+7, G+9, G+11) were developed in ETABS software.

• Soft stories were introduced at different levels in each building to study seismic behavior.

• Linear static, linear dynamic, and nonlinear static (pushover) analyses were used.

• Soil type: Medium-II, Seismic zone: V, Response reduction factor: 4.

Pushover Analysis:

• A nonlinear static method that applies gradually increasing lateral loads until a target displacement or failure.

• Provides insight into plastic hinge formation, force redistribution, and structural limit states.

• More practical and faster than full dynamic analysis for design purposes.

Models and Findings

1. Soft story at G+1: Story stiffness variation ~92%, behaves as a soft story.

2. Soft story at G+3: Stiffness variation ~84%, acts as a soft story.

3. Soft story at G+5: Stiffness variation ~142%, behaves as a soft story.

4. Soft story at G+7: Stiffness variation ~128%, acts as a soft story.

Key Observations:

• A story with stiffness variation >70% is identified as a soft story.

• The position of the soft story significantly affects the building’s seismic performance.

• Pushover analysis allows evaluation of lateral load distribution, plastic hinge formation, and potential weaknesses in buildings with soft stories at different levels.

Conclusion

In the present study, the nonlinear response of a reinforced concrete (RC) high-rise frame building with a soft storey located at different levels, in addition to the ground floor, was analyzed using ETABS under seismic loading. The main objective was to evaluate the variation in the load–displacement behavior and to determine the maximum base shear and displacement of the frame when the soft storey is placed at different elevations. The formation of plastic hinges was examined for configurations with a ground-floor soft storey and with soft storeys at higher levels, and hinge development was observed at various displacement stages. In a well-planned building without a soft storey irregularity, plastic hinge formation typically initiates at the beam ends and base columns of the lower storeys, then gradually propagates to the upper storeys, followed by yielding of interior intermediate columns in the upper levels, maintaining a desirable ductile mechanism. However, the comparison of models in this study reveals that the pattern of plastic hinge formation changes significantly with the location of the soft storey. When the soft storey is positioned at lower levels, hinge formation is more intense and severe, whereas shifting the soft storey to higher levels reduces the concentration and severity of hinges within that storey. Since the modeled building in this study is relatively stiff, only a limited number of hinges formed, and most remained within the Life Safety (LS) performance level. In less stiff structures, hinges may propagate up to the Collapse Prevention (CP) level or even beyond, indicating more severe damage. The results show that when the soft storey is located at the bottom of the building, hinge severity and the number of hinges are significantly higher compared to cases where the soft storey is placed at upper levels. As the soft storey is shifted upward, both the number and severity of hinges decrease, which is beneficial for structural performance. Additionally, moving the soft storey from lower to higher levels results in a reduction in overall structural displacement and base shear. In terms of effective damping, shifting the soft storey upward leads to a decrease in effective damping, which corresponds to reduced structural damage. Therefore, when the soft storey is located at lower levels, the structure experiences maximum damage, while placing it at higher levels results in comparatively less damage. Based on these observations, it is advisable to provide a soft storey at higher levels rather than at the bottom of the structure to achieve improved seismic performance.

References

[1] IS 1893 (Part 1):2016 Criteria for Earthquake Resistant Design of Structures, Part 1, General Provisions and Buildings [2] IS 456 (2000): Plain and Reinforced Concrete [3] FEMA 356: Prestandard and Commentary for the Seismic Rehabilitation of Buildings [4] FEMA 440: Improvement of Nonlinear Static Analysis Procedures [5] ATC 40: Seismic Evaluation and Retrofit of Existing Buildings [6] ASCE 41-31: Seismic Evaluation and Retrofit of Existing Buildings [7] Pushover Analysis of Building using Soft Storey at Different Levels, Mr. Prathamesh Sonawane, Dr. M.P. Wagh, Volume 7 Issue 5 – May 2021www.ijsart.com [8] Review on Pushover Analysis of Building Using Soft Storey at Different Level, Nilesh Bharat Vidhate, G.A. Sayyed, Volume 7 Issue 2, February 2021www.ijsart.com [9] Comparative Study on Reducing Soft Storey Effect in RC Structures, Mostafa Mahumud, Md Faiyaz Shahriar, Akib Mohammad Sunny https://doi.org/10.2991/978-94-6463-672-7_7 [10] A Review on Seismic Analysis of RCC Building with Soft Storey at Different Level, Alhat Sneha Dnyananeshwar, D.N. Mandik, V.P. Bhasure, N.V. Khadake, IJRESM Volume 5, Issue 2, February 2022 https://www.ijresm.com | ISSN (Online): 2581-5792 [11] Design and Analysis of High-Rise Buildings using ETABS, Jenita Kuriakose, Sreya Shaji, Roshan Daniel, Jitu Sreekuman, IJERT Volume 11, Issue 02, 2023www.ijert.org [12] Analysis of RCC Building with Multiple Soft Storey using ETABS, Omkar P. Khandagle, Prof., Jayant S. Kanase, IJRES Volume 10 Issue 6, 2022 www.ijres.org [13] Preventing Soft Storey Irregularity in RC Building by Pushover Analysis, Md. Abdul Alim, Nazrul Islam, IEB 49 (2) 13 October 2021 [14] Pushover Analysis of Reinforced Concrete Frames, Mila Svilar, Aleksandar Prokic, SERBIA 23-24 April 2019 CONFERENCE PROCEEDINGS INTERNATIONAL CONFERENCE (2019) [15] Nonlinear Static Pushover Analysis of Medium Rise and High-Rise Building, Dr, M. Keshava Murthy, Ashwini L K, Volume 6, 20 May 2019 https://doi.org/10.32628/IJSRST1196337\\ [16] Comparative study Nonlinear Pushover Analysis and Displacement Based adaptive Pushover Analysis Method, Int. J. Structural Engineering, Rutvik Sheth, Jayesh Prajapati, Devesh Soni, Vol. 9, No. 1, 2018 [17] M.Hafezolghorani, F. Hejazi, R. Vaghri, M.S. Bin Jaafar, and K. Karimzade, “Simplified damage Plasticity Model for Concrete”, in Structural Engineering International, 2017. DOI: 10.2749/1016816X1081. [18] C.P. Pantelides, C. Clyde, and L.D. Reaveley, “Performance-Based Evaluation of reinforced concrete building exterior joints for seismic excitation”, Earthquake Spectra, Vol. 18, No. 3, pp.449-480, 2002. [19] ASCE “American Society of Civil Engineers, Fema 356 Prestandard and Commentary for the Seismic Rehabilitation of Building”, Rehabilitation, no. November, 2000. [20] T. Paulay and R. Park, Reinforced Concrete Structures. John Wiley and Sons, 1975. [21] W. W. L. Chan, “The ultimate strength and deformation of plastic hinges in reinforced concrete frameworks”, ASCE J Struce Div, vol. 106, no. 5, 1980, DOI: 10.1061/jsdeag.0005416. [22] H. E. H. Roy and M. A. Sozen, “Ductility of Concrete”, Special Publication, vol. 12, pp. 213-235, 1965. [23] T. Paulay and M. J. N. Priestly, Seismic Design of Reinforced Concrete and Masonry Buildings. 1992. DOI: 10.1002/9780470172841.sssss

Copyright

Copyright © 2026 Shruti G. Kathi, Dr. Chirag R. Odedra, Dr. Kalpesh L. Kapadiya, Vandit Bhatt, Purna B. Vachhani. 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.