Effects of Differential Axial Shortening in Highrise Structures

Abstract

This research explores the challenge of differential axial shortening (DAS) in high rise buildings, a phenomenon that can disrupt vertical alignment and serviceability if not properly addressed. The study examines how DAS is influenced by three key factors: material choice, lateral load resisting systems (LLRS), and construction sequence analysis. To capture realistic behavior, structural models were developed with reinforced concrete (RCC) columns, composite concrete filled steel tube (CFT) columns, and shear walls, and tested under three scenarios—Dead Static, Linear Static, and Nonlinear Construction Sequence (NCS)—all in line with IS 16700:2023 serviceability requirements. The findings highlight that materials account for about 40% of DAS variation. RCC members showed the greatest long term shortening due to creep and shrinkage, while composite columns consistently performed better, achieving up to 76% reduction when paired with shear walls. The structural system contributed around 25%, with Tube in Tube systems balancing core and perimeter, Bundled Tubes showing localized differences, and Outrigger systems redistributing forces most effectively—though at the cost of higher axial demands in perimeter columns. Construction sequence effects contributed about 20%, with staged analysis improving prediction accuracy by roughly 35% compared to static models. Broader system level consequences (?10%) included load redistribution and secondary stresses in slabs and beams, while practical strategies (?5%) such as preset elevations, outrigger stiffness tuning, and material mixing proved effective in reducing DAS impacts. In summary, the study demonstrates that composite columns, especially when combined with shear walls and staged construction, provide superior control of DAS. By quantifying the contributions—materials (40%), LLRS (25%), construction sequence (20%), system consequences (10%), and mitigation strategies (5%)—this work offers clear, actionable guidance for structural engineers aiming to improve vertical alignment, serviceability, and long term performance in tall buildings.

Introduction

Concrete is widely used in tall building construction, where vertical elements like columns and shear walls experience axial shortening due to elastic deformation, creep, and shrinkage. These time-dependent effects cause differential axial shortening (DAS), where different structural elements shorten by different amounts. This can lead to structural distortions, sloping floors, cracking of beams and slabs, damage to façade and partitions, and malfunction of services such as elevators and pipes. The magnitude of shortening depends on factors such as reinforcement content, concrete properties, load distribution, construction sequence, environmental conditions, and building height.

Differential axial shortening occurs because columns and walls have different stiffness, cross-sections, and load levels. It becomes more significant in high-rise buildings, where cumulative deformation increases with height. Time-dependent phenomena like creep (slow deformation under sustained load) and shrinkage (volume reduction due to hydration and moisture loss) play a major role in this process.

To control building drift and improve structural stability, outrigger systems and belt trusses are often used. These systems connect the core of the building to exterior columns, creating a restoring force that reduces bending and lateral displacement. Modern high-rise structures also use concrete-filled tube (CFT) columns, which provide improved strength, durability, seismic resistance, and fire performance.

The literature review highlights that creep and shrinkage are the most critical factors affecting column shortening. Studies show that staged construction analysis with time-dependent effects provides more accurate results than traditional one-step analysis because loads are applied gradually during construction.

The methodology of the study analyzes axial shortening in different tall building configurations using ETABS software. A total of 18 theoretical building models (30, 40, and 50 storeys) were studied, including RCC and composite structures with tube-in-tube, bundled tube, and outrigger systems. Buildings were modeled with realistic parameters such as 20 m × 24 m plan dimensions, seismic zone IV conditions, and wind speed of 44 m/s. Time-dependent concrete properties were evaluated using the ACI 209R-2008 model.

The results analyze vertical displacement and drift values of the structures. The findings show that axial shortening increases with building height and varies depending on structural systems and construction sequence. Proper modeling of creep, shrinkage, and staged construction is essential to accurately predict deformation and ensure serviceability, structural safety, and long-term performance of high-rise buildings.

Conclusion

1) In high-rise buildings, vertical elements with RC shows up to 50% more differential axial shortening in linear static case compared to composite. 2) Among LLRS configurations, in bundled tube buildings, differential axial shortening drops by 31–53% compared to tube-in tube, with RC and Composite performing almost identically when the grade of concrete is increasing, differing only by 10–20%, while Outrigger buildings provides enhanced control of shortening with up to 70-76% by redistributing axial forces. 3) Incorporating non-linear construction sequence analysis (NCS) significantly reduces differential axial shortening with reductions ranging from 10-76% across tube-in-tube, bundled tube and outriggers. 4) Stage-by-stage construction and outrigger installation timing strongly influence differential axial shortening patterns. “All-at-once” analysis underestimates differential axial shortening, while construction sequence analysis reveals realistic redistribution and peak differentials. Sequence-aware modeling improves prediction accuracy and highlights critical stages where deferential axial shortening can be mitigated. 5) It is concluded that composite consistently perform better than RC, composite with non-linear construction sequence analysis provides the most reliable control of differential axial shortening.

References

[1] Lu, X. (2009). \"Shaking table model tests on a complex high-rise building with two towers of different height connected by trusses.\" Structural Design of Tall and Special Buildings Vol 18(7), 765-788. [2] Luong, A., and Kwok, M. (2012). \"Finding Structural Solutions by Connecting Towers.\" CTBUH Journal (III), 26-31. [3] McCall, A. J.T. (2013). \"Structural Analysis and Optimization of Skyscrapers Connected with and Atria\". All Theses and Dissertations. Paper 3829. [4] Nishimura, A. (2011). \"Base-isolated super high-rise RC building composed of three connected towers with vibration control systems.\" Structural Concrete, 12(2), 94-108. [5] Abada, G. (2004). \"2004 On Site Review Report: Petronas Office Towers, Kuala Lumpur, Malaysia.\" [6] The Magazine of Institution of Engineers, (2010). \"The Pinnacle@Duxton.\" The Singapore Engineer Civil and Structure. Infrastructure. Environmental Edition, citeseerx.ist.psu.edu/viewdoc [7] Kiran, M.U., Shivananda, S. M., and Mahantesha, O. (2016). “A Study of Lateral Drift Controlling Between Two Buildings by Connecting Sky-Bridge.” International Journal of Civil and Structural Engineering Research., 4(1), 266-273. [8] Wood, A., Wan-Ki, C., and McGrail, D. (2005). “The Skybridge as an Evacuation Option for Tall Buildings in High-Rise Cities in the Far East.” Journal of Applied Fire Science, Vol 13(II), 113-124. [9] Qing Lyu, and Wensheng Lu., (2019). “Mechanism and optimum design of shared tuned mass damper for twin-tower structures connected at the top by an isolated corridor.” Structural of Design Tall Special Buildings Vol 29(8),1-19.52 [10] Wei Guo, and Zhipeng Zhai., (2019). “Shaking table test and numerical analysis of an asymmetrical twin?tower super high?rise building connected with long?span steel truss.” Structural of Design Tall Special Buildings Vol 28(13).,1-27. [11] Sayed Mahmoud., (2019). “Horizontally connected high-rise buildings under earthquake loadings.” Ain Shams Engineering Journal Vol 10,227-241 [12] Xin Nie, and Congzhen Xiao., (2017). “Connection bridge effect on a DNA like two? spiral?up?tower building.” Structural of Design Tall Special Buildings Vol 26(13),1-11. [13] SUN Huang-sheng, and Mo-han., (2014). “Connecting parameters optimization on unsymmetrical twin-tower structure linked by Sky-Bridge.” Central South University Press and Springer-Verlag Berlin Heidelberg 2014,2460-2468. [14] Verma, S.K.(2014). “Wind loads on structurally coupled through single ridge tall buildings.” International Journal of Civil and Structural Engineering., Vol 4(3), 469-476. [15] Ying Zhou, and Xiling Lu., (2011). “Study on the seismic performance of a multi- tower connected structure.” Structural of Design Tall Special Buildings. Vol 20, 387–401. [16] Akira Nishimura, and Hiroshi Yamamoto., (2011). “Base-isolated super Highrise RC building composed of three connected towers with vibration control systems.” Structural Concrete Vol 12,94-108. [17] Xilin Lu, and Linzhi Chen., (2009). “Shaking table model tests on a complex high-rise building with two towers of different height connected by trusses.” Structural of Design Tall Special Buildings,765-788 [18] IS: 456 (Bureau of Indian Standards)., (2000). Indian Standard Plain and Reinforced Concrete Code of Practice (Forth Revision).53 [19] IS: 16700 (Bureau of Indian Standards)., (2016). Indian Standard Criteria for Structural Safety of Tall Concrete Buildings.20. IS:1893 (Bureau of Indian Standards)., (2016). Indian Standard Criteria for Earthquake Resistant Design of Structures. Part I General Provisions and Buildings (Sixth Revision). [20] IS:875 (Bureau of Indian Standards)., (1987). Indian Standard Code of Practice for Design Loads for Buildings and Structures Part II Imposed Loads (Second Revision). [21] IS:875 (Bureau of Indian Standards)., (2015). Indian Standard Code of Practice for Design Loads for Buildings and Structures. Part III Wind Loads. [22] IS:1893 (Bureau of Indian Standards)., (2016). Indian Standard Code of Practice for Criteria for Earthquake Resistant Design of Structures (Sixth Revision). [23] Fintel, Mark, S. K. Ghosh, and Hal Iyengar. Column Shortening in Tall Structures: Prediction and Compensation. Portland Cement Association, 1987.

Copyright

Copyright © 2026 Adiba Nishath, Dr Mohd Zaker, Dr. Mir Iqbal Faheem. 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.