Structural Performance Evaluation of Multi Storey Building, Considering Soil Structure Interaction for Different Soil Conditions using Tekla Structural Designer

Abstract

During an earthquake, seismic waves travel from the fault plane through the soil to the structure, creating relative motion between the foundation and superstructure—known as Soil-Structure Interaction (SSI). This study analyses the dynamic response of a multi-storey building under seismic loads, focusing on modal, drift, sway, shear, and reinforcement characteristics. The fundamental time period across all cases ranges between 1.23–1.33 seconds, with frequencies of 0.75–0.81 Hz. The first two modes contribute over 78–82% of mass participation, while higher modes account for about 11–12%, indicating a well-represented dynamic behaviour. Storey drift values remain within 1–2 mm, confirming stiffness and stability as per IS 1893 standards. Sway in both directions is nearly identical, showing excellent structural symmetry, with top floor sway varying between 53–96 mm across cases. Storey shear patterns demonstrate predictable behaviour—maximum at upper levels and gradually decreasing toward the base—ensuring efficient lateral load transfer. Reinforcement analysis reveals that beams and columns contribute the majority of steel consumption, with total reinforcement ranging from 201–360 tonnes. Overall, the structure exhibits-controlled deformation, adequate strength, and reliable seismic performance, satisfying both stability and safety requirements.

Introduction

SSI describes the two-way influence between a building and the supporting soil: flexible soil affects structural response, while the structure alters soil behavior. Variations in soil properties can cause differential settlements, affecting axial forces and bending moments. SSI effects are critical for heavy structures on soft soils (e.g., skyscrapers, nuclear plants) and are particularly relevant during earthquakes. Lighter structures on stiff soils often allow SSI to be neglected.

Tekla Structural Designer (TSD):
TSD is an advanced software that integrates structural analysis and design in a single 3D model, streamlining the workflow for engineers compared to traditional separate tools.

Project Overview:

• Building: Commercial, G+7, 625 m², 26.4 m height, square shape

• Soil Types: Soft, medium, and hard

• Foundations: Isolated footings, mat foundation, pile foundation

• Materials: Concrete M30, Steel Fe 550, slab thickness 0.23 m

• Analysis: Response Spectrum Analysis (RSA) under static (dead, live) and dynamic (seismic, Zone II) loads

Results – Modal Analysis:

• Structures on soft soil show the longest vibration period (1.31 s) and lowest natural frequency (0.75–0.81 Hz), indicating more flexible behavior.

• Medium soil slightly increases stiffness (time period 1.33 s).

• Hard soil provides the shortest time period (1.236 s), highest frequency, and greater modal mass participation, implying better seismic performance and stability.

• Dynamic response is more efficiently distributed on hard soil.

Conclusion

In this study, we examined how the structure behaves on different soil conditions in RSA seismic design on soft, medium and hard soil conditions. The results were compared through tables and graphs, which provided clear understanding of structural response on different soil conditions, based on these observations the following conclusions were drawn. 1) In soft soil, the maximum time period is 1.31 s, while for medium soil increases to 1.33 s, for hard soil reduces to 1.236 s. This indicates structure on soft soil experience longer vibration cycles due to low stiffness, whereas hard soils enhance stiffness, thereby reducing time period. Correspondingly, the natural frequencies ranges between 0.75 Hz to 0.81 Hz, with higher frequency observed in hard soil. The maximum modal mass also increases gradually from soft (37889.4 kN) to hard soil (38618.9 kN), implying enhanced stability. Overall, hard soil provides better seismic performance due to shorter time periods, high frequencies, and greater modal mass participation. 2) The seismic drift values shows that building performs consistently across all soil types in both direction 1 and 2. The maximum drift is only 2 mm which reflects strong lateral stiffness and stability. This consistency suggest that soil conditions have little effect on drift performance in this case. Such low drift values ensure the building remains safe, durable and comfortable for occupants. 3) For soft soil, the maximum sway values are nearly equal in both directions, around 93.5 mm, with a twist of 1 mm. This suggests higher flexibility and greater lateral movements due to reduced stiffness in supporting soil. In contrast, medium soil shows significantly reduced sway values, about 53.6 mm in both directions, while maintain the same twist. This reduction demonstrates that medium soil offers better resistant to lateral displacement, improving overall stability. Interestingly, for hard soil, the sway values increase again, reaching 96.4 mm and 96.9 mm in two directions, with constant twist of 1 mm. this higher sway on hard soil may be attributed to increased stiffness transferring greater seismic energy to structure. 4) On soft soil the structure takes very high forces in one direction (414.54 kN) while the other direction carries very little (31.7 kN). This means building tends to sway more strongly in a single direction on soft ground. On medium soil situation is different. The forces in first direction are lower (75.38), but in second direction they become high (422.75 kN). On hard soil, the forces in first direction are again high (308 kN), but in the second direction they are almost zero (0.01 kN). Overall, study proves that soil type greatly changes how forces are shared, with medium soil offering most stable and balanced response. 5) In soft soil, shear force is highly concentrated in Direction 1, reaching 2191.57 kN, while Direction 2 remains lower at 167.61. this indicates that soft soil amplifies shear along one primary axis. In medium soil, the behaviour is reversed with direction 1 shear dropping significantly to 404.46 kN, but Direction 2 rising to 2270.04 kN. This shift highlights that medium soil condition redistribute shear more heavily along second direction. For hard soil, shear in Direction 1 is again considerably high at 1655.80 kN, while Direction 2 is negligible at 0.04 kN, showing imbalance. Overall, results prove that soil conditions strongly control how shear forces act, with medium soil creating the highest demand in Direction 2, while soft and hard soils concentrate forces in Direction 1. 6) The reinforcement quantities vary considerably with soil type, reflecting how foundation interaction influences material demand. medium soil conditions generate higher stresses within the structural system, leading to the need for additional reinforcement to maintain safety and serviceability. The results also indicate that while soft and hard soils produce similar reinforcement requirements, medium soil imposes more critical design demands due to its stiffness characteristics. In conclusion, material usage is highly sensitive to soil conditions, with medium soil creating the most reinforcement-intensive design, highlighting the importance of soil–structure interaction in overall construction planning.

References

[1] Arshad Jamal and Jadhav H S (2019) “Evaluation of R.C. Multi-storey Building Response under the Effect of Soil-Structure Interaction” International Research Journal of Engineering and Technology (IRJET), Vol. 6, Issue 4, e-ISSN: 2395-0056, p-ISSN: 2395-0072. [2] Paraskevi K. Askouni and Dimitris L. Karabalis (2022) “The Modification of the Estimated Seismic Behaviour of R/C Low-Rise Buildings Due to SSI” Buildings Vol. 12, Issue 7. [3] Pandi mani and Tanikonda Siva Sankar (2023), “Impact Assessment of SSI on the Structural Performance of RC Buildings under Lateral Forces” Research square, ISSN 2693-5015. [4] P.Nagasri Anjaneyulu and Dr. Dumpa Venkateswarlu (2021), “Analysis and Design of Reinforced Concrete Multi-Stored Building (G+5) by using Tekla Software” International Journal for Modern Trends in Science and Technology, ISSN: 2455-3778. [5] Rahul Raghunath Kharade and Nagendra M V (2020), “Study of Soil Structure Interaction on Framed Structure using ETABS” International Research Journal of Engineering and Technology (IRJET), Vol. 7, Issue 8, e-ISSN: 2395-0056, p-ISSN: 2395-0072. [6] IS 800.2007, \"Indian Standard Code of Practice for General Steel Construction\", Bureau of Indian Standards, New Delhi, India. [7] IS 875 (Part 1)-1987. \"Indian Standard Code of Practice for Design Loads (Other than Earthquake) for buildings and Structures. Part 1 - Dead Loads-Unit weights of building materials and stored materials\", Bureau of Indian Standards, New Delhi, India. [8] IS 875 (Part 2)-1987, \"Indian Standard Code of Practice for Design Loads (Other than Earthquake) for buildings and Structures. Part 2-Imposed Loads- Unit weights of building materials and stored materials\", Bureau of Indian Standards, New Delhi, India. [9] IS 1893 (Part 1)-2016 \"Criteria for Earthquake Resistant Design of Structures\", Bureau of Indian Standards, New Delhi, India. [10] IS 6403: 1981 – Code of practise for determination of bearing capacity of shallow foundations.

Copyright

Copyright © 2025 Vinayaka P A, Savan R G Basavaraj. 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.