Adapting IS 1893 (2023) for the Nepalese Seismic Context: Evaluating Base Shear Coefficients
Keywords:
IS 1893:2023, NBC 105:2020, Seismic codes, Base shear coefficients, Comparative study, RC buildingsAbstract
This study investigates the applicability of draft IS 1893:2023 for the seismic design of RC buildings in Nepal, focusing on the base shear coefficients for ‘Zone VI’ bordering Nepal on three sides. Key changes in the code are highlighted that control the design base shear coefficient. One of them is the shift from Deterministic Seismic Hazard Assessment (DSHA) to Probabilistic Earthquake Hazard Assessment (PEHA), which has significantly increased the seismic zone factor. Other changes include updated site classifications, the introduction of serviceability checks, reformed acceleration response spectra, and the provision of minimum design horizontal base shear. The base shear coefficients were obtained using IS 1893:2023 for zone VI for different variations of site categories, structural systems, and importance classes. The obtained coefficients from the code were then compared with the existing NBC 105:2020 and IS 1893:2016 under the fundamental periods. Overall, the base shear coefficients from the IS 1893:2023 (SD) code were found to be the highest in all scenarios followed by the NBC 105:2020 (ULS). Significant margins in the coefficients were seen between these two for the RC SMRF buildings. However, for the dual systems - RC shear wall & RC SMRF buildings, narrow margins were seen. The study reveals implementing IS 1893:2023 in Nepal (Zone VI) would notably increase the base shear, resulting in a potentially more earthquake-resistant design, but also higher construction costs.
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