Comparative Analysis of Outrigger Systems in High-Rise Building

Abstract

The significant increase in the world population and emigration of human beings to the cities for amenities and employment opportunities, the land crisis has emerged as serious issues for humankind. For resolution structural engineer begin to build high-rise buildings to accommodate the current population. Height increase of building direct impact on increase of lateral forces on high buildings. The concept of illumination of outrigger structural systems is evaluated by comparing multiple X braced, N Braced, Inv V Braced outrigger system and shear wall system models types utilizing a 40-story reinforced concrete building using ETABS software.

Introduction

Urban population growth and limited land availability have driven vertical expansion in cities, resulting in the construction of low-, medium-, and high-rise buildings. The structural analysis and design of tall buildings require advanced methods to withstand lateral loads such as wind and earthquakes. A key concern is minimizing side sway to maintain safety and structural integrity.

Core and Outrigger Structural System:

• Outriggers are rigid horizontal structural elements connecting the central core to peripheral columns, improving lateral stiffness and resistance to overturning.

• When the core tends to tilt under lateral forces, the outriggers activate tension-compression forces in the outer columns, producing a restoring moment.

• The system’s performance depends on the relative stiffness of the core, outriggers, and columns—force distribution cannot be arbitrarily assigned.

• Figure 1.1 illustrates the structural behavior and compares moment diagrams with and without outrigger bracing.

General Considerations for Analysis:

• Model: 40-story symmetric building with a 20 m × 20 m floor plan.

• Floor height: 3 m; column spacing: 5 m.

• Seismic Zone: V (high seismic risk)

• Soil Type: II (medium soil condition)

• Key parameters analyzed:

  • Story displacement

  • Base shear

  • Natural time periods

  • Effects of placing outriggers at different floor levels

Conclusion

Based on the observations and the results obtained during this study, we can arrive at the following conclusions: 1) The use of outrigger system in high rise structure increases the stiffness and makes the structure more efficient under seismic. 2) It can be concluded from this study that the outrigger system provides reduction in displacement, drift and base moment and time period. 3) As the height of building increases then necessity of new structural system arises Outrigger structural system depends on number and its position throughout the height of the building. 4) The best performing model for dynamic assessment subjected to earthquake and wind load cases in a 40-storey Building when we use steel X type Bracing. 5) Outrigger performs well compared to rigid frame and core system.

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] IS 16700:2023 Criteria for Structural Safety of Tall Concrete Buildings. [4] Chambulwar, S., Kadam, T. S., Bhujbal, A. M., Konde, P. P., & Alandkar, S. B. (2021). Comparative study of RCC frame structure with and without outrigger system. International Journal of Research in Engineering and Science (IJRES), 9(6), 45–47. Retrieved from http://www.ijres.org [5] Sundar, R. S., & Gore, N. G. (2017). A study on tall RC structure with outrigger system subjected to seismic and wind loading. International Journal of Engineering Research & Technology (IJERT), 6(2), 515–520. http://www.ijert.org [6] Choi, H. S., Ho, G., Joseph, L., & Mathias, N. (2012). Outrigger design for high-rise buildings: An output of the CTBUH Outrigger Working Group. Council on Tall Buildings and Urban Habitat. Published by Routledge, Taylor & Francis Group. [7] Das, B. B., Barbhuiya, S., Gupta, R., & Saha, P. (Eds.). (2021). Recent developments in sustainable infrastructure: Select proceedings of ICRDSI 2019 (Vol. 75). Springer. https://doi.org/10.1007/978-981-15-4577-1\\

Copyright

Copyright © 2025 Kevin Patel, Dr. V. R. Patel. 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.