Seismic Analysis of G+20 Story Inclined Sky Bridge Building and Conventional Building

Abstract

Seismic analysis of adjacent buildings linked through Inclined sky bridges using ETABS 2021.This project aims to carry out the Seismic analysis of adjacent buildings connected at different levels with Inclined sky bridges. The study assesses selected alternatives by changing the position of Inclined sky bridges at three sections in height, mid-height (1/2), three quarter-height (3/4), and the top of the buildings. Both static and dynamic earthquake loading cases are imposed, based on the seismic codes, to evaluate inter-story drift, base shear and joint displacements. Buildings with and without sky bridges are compared to measure the effect of Inclined sky bridges. The study reveals the effectiveness of Inclined sky bridges on improving the seismic behaviour by judiciously locating Inclined sky bridges as Lateral displacement and storey drift are typically reduced when Inclined sky bridges are included.

Introduction

The rapid global population growth and urban migration have led to increased demand for residential and commercial space in cities, where land is limited and costly. As a solution, high-rise buildings have emerged, combining structural engineering, architecture, and urban planning. These skyscrapers symbolize modern urban living and often incorporate sky bridges—elevated structures connecting tall buildings.

Sky bridges enhance functionality, safety, and aesthetics. They ease pedestrian movement between towers, reduce elevator dependence, and serve as emergency evacuation routes. They also help reduce ground-level congestion and environmental impacts. Structurally, sky bridges are constructed using various materials like struts, reinforced concrete, or steel, based on design needs.

Notable examples include:

• Petronas Twin Towers (Malaysia): Sky bridge aids both safety and design.

• Sands Sky Park (Singapore): A 340-meter-long truss structure connecting three towers, shaped like a boat.

• Shanghai World Financial Center (China): The sky bridge contributes to structural stability and iconic form.

Numerical Study

A seismic analysis was performed on two identical 20-story buildings (height 61.5 m), connected by an inclined RCC sky bridge, using ETABS21 software. The structures are situated in seismic zone IV, and analyzed with the Response Spectrum method.

The study compares:

• Maximum storey drift

• Maximum base shear

• Maximum top storey lateral displacement

• Maximum storey displacement

These comparisons help evaluate how the sky bridge affects the buildings’ structural response during seismic events.

Conclusion

From results of the seismic analysis of two buildings connected by a skybridge, utilizing both the Static Equivalent Method and the Response Spectrum Method in ETABS software. The analysis focused on comparing the seismic performance of buildings with and without a skybridge connection, as well as evaluating the effectiveness of inclined skybridges. A. Impact on Base Shear • The addition of inclined skybridges generally increases the base shear of the connected buildings compared to standalone structures. B. Effect on Maximum Story Displacement • Inclined Skybridges are generally effective in reducing the maximum story displacement • A single inclined skybridge (SCB I15-12) shows a significant reduction of 31.28% in EQx and 40.85% in EQy, and 30.35% in RSx. C. Effect on Story Drift: • Building is connected by inclined sky bridge drift is reduction is more in direction of sky bridge, where sightly reduction in across direction. • SCB I20-17 consistently shows the highest percentage of drift reduction, starting from as high as 53.5%. Among the different configurations studied, the sky bridge located at the 10th floor (SCB I10) demonstrates the minimum overall displacement, indicating superior stiffness against lateral seismic forces. Conversely, the sky bridge at the 20th floor (SCB I20) results in the maximum percentage reduction in inter-story drift, highlighting its effectiveness in controlling relative movement between stories. However, the configuration with the inclined sky bridge at the 15th floor (SCB I15) offers a well-balanced performance, achieving both significantly reduced displacement and drift.

References

[1] IS 1893:2016 (Part-1) Criteria for earthquake-resistant design of structures. [2] IS 875:2015 (Part-3) Design Loads (other than Earthquake) for Buildings and Structures-code practice [3] IS 456:2000, Plain and Reinforced Concrete – Code of Practice, Bureau of Indian Standards, New Delhi, India. [4] Nisarg Patoliya, Indrajit N., Agrawal, Vimlesh V., \"Seismic Analysis of Tall Buildings Connected with Sky Bridge\", International Advanced Research Journal in Science, Engineering and Technology, 2023. [5] Hussain, Syed Adnan, Azeem, M. A., Minhajuddin, Ahmed, \"Effect on Seismic Behavior of Structurally Connected Tall Buildings\", International Journal of Engineering Research and Applications, 2022. [6] Nahid Islam Romel, Md. Mohiuddin Ahmed, Quazi Reduanul Bari, Badhan Chakma, \"Optimum Location Determination of a Horizontally Connected Steel Bridge for a G+10 Storied RCC Building Under Lateral Loads\", School of Applied Sciences & Technology, SUST, Sylhet, January 2023. [7] Kiran M.U, Shivananda S.M, Mahantesha O., \"A Study Of Lateral Drift Controlling Between Two Buildings By Connecting Sky Bridge\", International Journal of Civil and Structural Engineering Research, 2016. [8] Chandan Ahir, Neeraj Singh Bais. \"Research on the Effect of Horizontal Walkway Location Connecting Two High-Rise Buildings (G+20) Under Seismic Loading,\" International Research Journal of Engineering and Technology (IRJET),2024 [9] D.C.P. Ng, M.P Anwar, T.L. Lau, W. Elleithy, A.A. Mohammed, J. Jayaprakash, \"Dynamic Response Analysis of Skybridge Connected Reinforced Concrete Buildings under Lateral Loads\", International Journal of Civil Engineering and Technology,2024.

Copyright

Copyright © 2025 Hemanshukumar A. 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.