The seismic behaviour of reinforced concrete (RCC) buildings is strongly influenced by structural irregularities, stiffness variation and overall building configuration. This research evaluates the seismic response of mid-rise RCC structures with different plan and vertical irregularities under earthquake conditions relevant to Bhutan. Structural models including regular, L-shaped and T-shaped buildings were analysed using Response Spectrum Analysis in ETABS according to IS 1893 (Part 1):2016 provisions. The effect of masonry infill walls was incorporated through equivalent diagonal strut modelling. Different structural cases, including soft-storey conditions, were examined to assess their influence on seismic performance. Important response parameters such as storey displacement, inter-storey drift, base shear and stiffness were compared for all models. The analysis showed that irregular structures are more vulnerable to seismic effects due to increased torsion and deformation demands, whereas infill walls improve stiffness and reduce lateral movement. The study emphasizes the need for proper seismic design and stiffness distribution in earthquake-resistant RCC buildings.
Wangdi et al. (2026) studied this question.