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Seismic Vulnerability and Torsional Amplification in G+16 T-Shaped RC Structures
Subject area: Science,Engineering and Technology · Area of research: Seismic Analysis of RC Structures
Abstract
The increasing architectural demand for functionally diverse configurations has led to the widespread adoption of asymmetric structures, such as T-shaped buildings, which inherently possess plan irregularities. In these structures, the center of mass (CM) and the center of rigidity (CR) do not naturally coincide, leading to significant eccentricity and severe lateral-torsional coupling during seismic events. This study investigates the torsional behaviour and dynamic response of a G+16 multi-story, T-shaped reinforced concrete (RC) building. The structural framework was modelled and analyzed using ETABS software, employing Response Spectrum Analysis (RSA) in compliance with IS 1893:2016 guidelines for Seismic Zone 3. Critical response parameters, including maximum story displacement, base shear, story drift, and modal time periods, were evaluated to quantify torsional irregularities. The analytical results demonstrated a substantial shift of the CR towards the stiffer flange portion of the building, causing extreme torsional stress and dangerous stress concentrations specifically at the re-entrant corners. Under lateral seismic loading, the drift ratio (D_{max}/D_{avg}) indicated the presence of extreme torsional irregularities along the Y-direction. To mitigate these vulnerabilities, targeted structural interventions were evaluated; the findings confirm that the strategic placement of shear walls at re-entrant corners or the implementation of seismic joints effectively shifts the CR closer to the CM, thereby optimizing lateral stability and minimizing overall torsional rotation.
Keywords
Lateral-Torsional Coupling Vulnerability, CM-CR Eccentricity Analysis, Torsional Irregularity Ratio Evaluation, Response Spectrum Analysis ( (RSA),G+16 RC Frame Torsional Behaviour
References
[1] Gudainiyan, J., & Sharma, P. (2025). The Impact of a Near-Field Ground Motion on a T-Shaped Building. Department of Civil Engineering, GLA University. (Examines the non-linear time history analysis of T-shaped models and torsional irregularity under near-fault earthquakes).
[2] Bush, R. C., Shirkol, A. I., Sruthi, J. S., et al. (2022). Study of seismic analysis of asymmetric building with different shapes of staggered openings and without openings in Shear Wall. Materials Today: Proceedings. (Evaluates how the strategic placement of shear walls mitigates displacement and story drift in asymmetric structures).
[3] Patidar, G., & Singh, V. (2022). Dynamic Analysis of Multistorey RCC Building with Different Irregularities. International Journal for Research Trends and Innovation (IJRTI), 7(8). (Discusses roof displacement and time period variances in T-shaped configurations compared to regular building frames).
[4] Shelke, R. N. (2017). Comparison and Analysis of Multi-Storeyed Buildings of Various Configurations in Seismic Zones V. International Journal For Technological Research In Engineering. (Analyzes how story drift increases up to the first floor and decreases toward the top in various irregularly shaped buildings, including T-shapes).
How to cite this paper
@article{1715108,
author = {Ghorpade Pratik Sahebrao, Prof. Dr. Gunaware P. D., Prof. Khamkar R. S.},
title = {Seismic Vulnerability and Torsional Amplification in G+16 T-Shaped RC Structures},
journal = {Iconic Research And Engineering Journals},
year = {2026},
volume = {9},
number = {9},
pages = {917-923},
issn = {2456-8880},
url = {https://www.irejournals.com/formatedpaper/1715108.pdf},
abstract = {The increasing architectural demand for functionally diverse configurations has led to the widespread adoption of asymmetric structures, such as T-shaped buildings, which inherently possess plan irregularities. In these structures, the center of mass (CM) and the center of rigidity (CR) do not naturally coincide, leading to significant eccentricity and severe lateral-torsional coupling during seismic events. This study investigates the torsional behaviour and dynamic response of a G+16 multi-story, T-shaped reinforced concrete (RC) building. The structural framework was modelled and analyzed using ETABS software, employing Response Spectrum Analysis (RSA) in compliance with IS 1893:2016 guidelines for Seismic Zone 3. Critical response parameters, including maximum story displacement, base shear, story drift, and modal time periods, were evaluated to quantify torsional irregularities. The analytical results demonstrated a substantial shift of the CR towards the stiffer flange portion of the building, causing extreme torsional stress and dangerous stress concentrations specifically at the re-entrant corners. Under lateral seismic loading, the drift ratio (D_{max}/D_{avg}) indicated the presence of extreme torsional irregularities along the Y-direction. To mitigate these vulnerabilities, targeted structural interventions were evaluated; the findings confirm that the strategic placement of shear walls at re-entrant corners or the implementation of seismic joints effectively shifts the CR closer to the CM, thereby optimizing lateral stability and minimizing overall torsional rotation.},
keywords = {Lateral-Torsional Coupling Vulnerability, CM-CR Eccentricity Analysis, Torsional Irregularity Ratio Evaluation, Response Spectrum Analysis ( (RSA),G+16 RC Frame Torsional Behaviour},
month = {March},
doi = {https://doi.org/10.64388/IREV9I9-1715108}
}