Comparative seismic analysis of steel frame structures with conventional, castellated, and cellular beams

Modern seismic design of steel structures demands innovative approaches that optimize material strength while maintaining ductility and energy dissipation capacity. Introducing web openings into standard rolled sections, resulting in castellated and cellular beams, has emerged as an effective strategy to achieve these goals. By reducing self-weight and creating efficient load paths, these beams offer potential gains in structural performance under earthquake loading. This study examines the seismic response of a G + 9 steel moment-resisting frame configured with conventional, castellated, and cellular beams. Response Spectrum Analysis (RSA) is performed in ETABS software in accordance with IS 1893 (Part 1): 2016 provisions. Key response metrics such as lateral displacement, story drift, base shear, and time period are compared across the three beam configurations. Results indicate that both castellated and cellular beams outperform conventional sections: lateral displacements decrease by up to 37%, and story drifts reduce by up to 34%. Correspondingly, base shear values drop by up to 26.8%, signifying improved energy dissipation characteristics. The time period increases by approximately 40–42% for sections containing web openings, reflecting a trade-off between stiffness and flexibility. While these findings are promising, they are limited to linear dynamic analysis and idealized configurations. Overall, this research confirms that integrating castellated and cellular beams into steel frames can yield effective and economical improvements in seismic resilience.