The predominant building configurations in the seismically active Indian Himalayan region comprise of vertically irregular buildings located on hillside slopes. Buildings in hilly topography are often constructed with foundations at multiple levels, such as ones with foundations split at two levels or stepped foundations, requiring columns of varying height to accommodate the ground slope. This introduces vertical irregularity over the height of the structure, making them more susceptible to collapse as compared to regular buildings on flat grounds. To ensure the life safety of the building occupants, this study evaluates the adequacy of modern Indian seismic codes in preventing collapse under earthquake shaking, focussing on predominant hillside reinforced concrete building configurations located on plains, gradual slopes, and steep slopes. Incremental dynamic analysis is carried on nonlinear analytical building models, and seismic collapse fragility curves are developed. Fragility analysis indicates buildings located on a gradual slope with stepped foundation are most susceptible to collapse among all configurations, with median collapse capacity 31% lower than their counterparts on flat grounds. For this building configuration, parameters influencing collapse fragility metrics are further investigated through a multiple linear regression model. The study further investigates the seismic collapse risk of buildings located in different cities of the Indian Himalayan region using collapse margin ratio (CMR) and the probability of collapse in 50 years that is not investigated for Indian buildings previously. It is observed that probability of collapse in 50 years for buildings in most of the cities considered in the study is greater than 1%, exceeding the threshold of uniform building collapse risk as per US codes.

地震活跃的印度喜马拉雅地区的主要建筑结构由位于山坡上的垂直不规则建筑组成。丘陵地形的建筑物通常采用多层基础建造，例如地基分为两层或阶梯式基础，需要不同高度的柱子以适应地面坡度。这在结构的高度上引入了垂直不规则性，使它们与平坦地面上的常规建筑物相比更容易倒塌。为了确保建筑物居住者的生命安全，本研究评估了现代印度地震规范在防止地震晃动下倒塌方面的充分性，重点是位于平原、缓坡和陡坡上的主要山坡钢筋混凝土建筑配置。对非线性分析建筑模型进行增量动力分析，得到地震倒塌脆性曲线。脆弱性分析表​​明，在所有配置中，位于带有阶梯基础的渐变斜坡上的建筑物最容易倒塌，倒塌能力中值比平地上的建筑物低 31%。对于这种建筑配置，通过多元线性回归模型进一步研究了影响倒塌脆性指标的参数。该研究使用倒塌裕度比 (CMR) 和 50 年内倒塌的概率进一步调查了位于印度喜马拉雅地区不同城市的建筑物的地震倒塌风险，而此前印度建筑物并未对此进行调查。