This paper focuses on the seismic vulnerabilities of multi-storey buildings in hilly regions like Sikkim and Uttarakhand, where rapid construction is driven by population growth and tourism. The study particularly evaluates step-back buildings on hilly slopes, comparing their vulnerability to standard buildings on flat terrain. Using non-linear analysis to assess structural aspects like displacement and storey drift ratio, the research examines the performance of these buildings in both uphill and downhill orientations against typical three-storey and six-storey structures, respectively. The findings indicate that step-back buildings, especially those without infill walls, are more susceptible to seismic damage. For instance, on the uphill side, a step-back building shows a mean drift ratio 15.11% greater in the X direction and 4.57% greater in the Y direction compared to a three-storey regular building (3SR). This vulnerability is exacerbated when infill walls are absent, with mean drift ratios in step-back buildings being 74.75% and 33% higher in the X and Y directions, respectively. Moreover, at a seismic acceleration of 0.36 g, the mean displacement of a step-back building is 83% greater in the X direction and 51% greater in the Y direction than those with infill walls (SBIN), underscoring the significant role of infill walls in enhancing earthquake resilience. The study also highlights that short columns in step-back buildings are particularly prone to severe damage, especially just above the uppermost foundation level. While infill walls offer substantial mitigation of damage at the Design Basis Earthquake (DBE) level, at the Maximum Considered Earthquake (MCE) level, step-back buildings still endure severe damage compared to regular buildings with infill walls. Consequently, the research establishes that step-back buildings demonstrate greater vulnerability at DBE levels without infill walls and are more susceptible to damage than flat terrain buildings at MCE levels, emphasizing the need for careful design and reinforcement strategies in earthquake-prone hilly areas.

The recent introduction of IS 18168:2023 marks a significant advancement in the seismic design of steel structures in India by providing dedicated provisions for eccentrically braced frames (EBFs). While the code promotes link-controlled energy dissipation, its performance under different design philosophies, particularly in the nonlinear range, remains largely unexplored. This study presents a comprehensive seismic performance evaluation of steel EBF buildings designed as per IS 18168:2023 using conventional Force-Based Design (FBD) and Direct Displacement-Based Design (DDBD) approaches. The nonlinear static pushover analysis, nonlinear time-history analysis, and incremental dynamic analysis are performed for four building heights of 3-, 6-, 9-, and 12-storey. In addition, various important response parameters, including inter-storey drift, link rotation, plastic hinge distribution, variability, and collapse-related behaviour, have been systematically examined. Based on the results, it has been confirmed that EBF systems designed according to IS 18,168 exhibit a stable and desirable seismic behaviour, with inelastic deformation pretty much localized in the shear links. With respect to FBD, however, DDBD provides stronger control over nonlinear response due to approximately 20–40% lower median drift demands, 30–50% reduction at critical link rotation in MCE level, and strongly reduced record-to-record variability. Further, the drift escalation in DDBD frames is delayed while collapse robustness is notably improved, particularly for the midand high-rise buildings. Overall, the study brings out that though IS 18,168 provides a robust codal framework in the design of EBF systems, integrating DDBD within this codal context further leads to a more realistic, predictable, and performanceoriented seismic response, especially under strong ground motions.