Seismic Performance Evaluation of Multistoried RCC Building with Oblique Column

Abstract

Exploring innovative structural solutions to enhance seismic resilience in buildings is critical in advancing the field of modern structural engineering. This research contributes to this endeavor by analyzing the role of inclined columns within frame systems and their potential to strengthen the earthquake resistance of structures. This study assesses how variations in column inclination, configuration, and quantity affect seismicbehaviour. This research utilized response spectrum analysis and evaluated key seismic performance indicators, including story displacement, inter-story drift, base shear. These results high light the effectiveness of inclined columns in mitigating seismic risks, underscoring the need for careful consideration of their configuration to optimize structural resilience and their potential as a retrofitting measure.When viewed from the outside, buildings that make a certain angle to the ground and whose floor plans are horizontally offset could be defined as inclined-form buildings. Although these buildings present unique design opportunities, they present considerable challenges. This research contributes to advancing structural engineering practices by offering insights into the integration of inclined columns for seismic design, suggesting a promising direction for future building standards and construction methodologies, and retrofitting alternatives.

Introduction

Modern construction techniques have introduced complex building forms, including the use of inclined (slanted) columns—columns tilted away from vertical—which offer a potential alternative to traditional and expensive seismic protection devices like viscous dampers and base isolators. Inclined columns influence load paths by introducing second-order bending moments and horizontal load components, which can improve seismic resilience by distributing lateral forces more evenly, reducing inter-story drift, and enhancing energy dissipation compared to conventional moment-resisting frames.

Despite these benefits, current building codes lack specific guidelines for designing structures with inclined columns, and research on their seismic performance remains limited. This study investigates the behavior of buildings with oblique columns versus traditional vertical columns, focusing on lateral stability, overturning moments, and seismic response, particularly in high-rise buildings.

Using ETABS software, models of 12-story buildings with various column inclinations (80°, 84°, 86°, 88°, and 90° vertical) were created and analyzed for story displacement, shear, and drift under seismic loads. The study compares these parameters graphically and validates results with manual calculations on simpler models, aiming to understand the favorable and unfavorable impacts of inclined columns on structural behavior and promote their use in seismic-resistant design.

Conclusion

This study confirms that Oblique columns improve seismic performance in certain configurations by redistributing forces and reducing overall base shear. The maximum story drift reduces from approximately 0.0072 at 80° and 0.0025 at 90°, representing a 65.3% reduction. The top-story displacement decreases from around 205 mm to 48 mm, showing a 76.6% reduction.Story shear alsofollows this pattern, dropping from about 6600 kN 80° and 1800 kN at 90°, which accounts for a 72.7% reduction.Maximum drift of 80° 0.0072 and minimum drift of 90° 0.0025 showing a reduction of 65.3%.Compared to 80°, drift is reduced by over 75%, and it closely approaches the performance of the 90° vertical column.Top-story displacement at 88° is approximately 75 mm, compared to 205 mm at 80°.88° strikes a balance betweenvertical load efficiency and architectural inclination. Unlike 80° or 84°, which may cause more torsion, uneven stiffness, and stress concentrations, 88° remains close enough to vertical to avoid excessive lateral flexibility.Among the oblique column configurations, the 88° column performs the best in terms of reducing story drift, displacement, and shear, while still maintaining the architectural or structural benefits of an inclined system. It offers a good compromise between aesthetics and structural performance, and is therefore the most efficient choice for oblique column designs based on the current analysis.Base shear is consistently lower in buildings with oblique columns, indicating a reduced seismic force transfer to the foundation.

References

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Copyright

Copyright © 2025 Gomatesh Patil, Sakshi Lad, Pooja Sadamate, Nilam Powar, Shrishail Khanaj. 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.