ANALYSIS OF HIGH-RISE BUILDING BY COMPARING FOOTING WITH BASE ISOLATION AND WITHOUT BASE ISOLATION USING ETABS

A controlled ETABS comparison of square and T-shaped G+40 RCC buildings shows that LRB base isolation provides substantial improvement over conventional fixed footing. The standardized dataset gives roof-displacement reductions of 37.8% for the square plan and 35.1% for the T-shaped plan. Maximum drift reductions are larger, reaching 46.4% and 43.8%, respectively. Primary ETABS base-shear summaries show reductions between 39.56% and 43.43%. The first-mode period increases from 3.20 s to 5.80 s and frequency decreases from 0.31 Hz to 0.17 Hz, confirming effective period elongation and seismic decoupling. Cumulative modal mass participation exceeds 90% in both horizontal directions for every model. The square isolated building performs best because isolation reduces seismic input and plan symmetry limits torsional amplification. The T-shaped isolated model also improves markedly, but its re-entrant geometry requires additional attention to diaphragm forces, torsional response and local member demand. Practical implementation should include nonlinear bearing verification, maximum isolator displacement, stability under gravity load, seismic gap, wind serviceability, utility flexibility and soil–structure interaction. Final construction design must be based on complete ETABS exports, code-compliant load combinations and project-specific geotechnical data.

[1] Bureau of Indian Standards, IS 1893 (Part 1): 2016, Criteria for Earthquake Resistant Design of Structures—General Provisions and Buildings. New Delhi, India: BIS, 2016. [2] Bureau of Indian Standards, IS 875 (Part 3): 2015, Design Loads (Other Than Earthquake) for Buildings and Structures—Wind Loads. New Delhi, India: BIS, 2015. [3] Bureau of Indian Standards, IS 456: 2000, Plain and Reinforced Concrete—Code of Practice. New Delhi, India: BIS, 2000. [4] T. Li, R. Liu, G. Sun, and W. Sun, “Seismic performance of high-rise shear walls with hybrid control: Sparse isolation bearings and viscous fluid dampers,” Buildings, vol. 16, no. 1, Art. no. 208, 2026, doi: 10.3390/buildings16010208. [5] A. K. Tiwary, H. Singh, N. Kedia, A. K. Dasarathy, H. L. Yadav, P. Das, and G. V. Jasmine, “Comparative study of single and multi-outrigger systems for enhanced lateral stability in high-rise structures,” J. Build. Pathol. Rehabil., vol. 11, Art. no. 6, 2026, doi: 10.1007/s41024-025-00682-w. [6] Z. Adnan and A. S. Mahmoud, “Evaluation of pounding response in reinforced concrete buildings with various base isolators,” IOP Conf. Ser.: Earth Environ. Sci., vol. 1545, Art. no. 012082, 2025, doi: 10.1088/1755-1315/1545/1/012082. [7] G. Zhao et al., “Seismic response analysis of double-layer isolation structures under earthquake actions,” Buildings, vol. 15, no. 8, Art. no. 1292, 2025, doi: 10.3390/buildings15081292. [8] Y. Ren et al., “Numerical simulation analysis of lead rubber bearings considering large-deformation damage,” Buildings, vol. 15, no. 5, Art. no. 839, 2025, doi: 10.3390/buildings15050839. [9] M. A. Q. Al-Janabi et al., “A global review of seismic isolation and energy dissipation systems for resilient structures,” Sustainability, vol. 17, no. 16, Art. no. 7314, 2025, doi: 10.3390/su17167314. [10] W. A. Ghafar, T. Zhong, Z. Lai, Z. Pingle, Y. Yang, and M. M. Hasan, “Seismic isolation for existing structures: A review of retrofitting techniques, case studies, and trends,” Discover Civil Engineering, vol. 2, Art. no. 137, 2025, doi: 10.1007/s44290-025-00300-1.