Structural challenges for seismic stability of buildings in hilly areas

Buildings on hills behave dynamically, very different from buildings on flatlands. Due to irregularity in horizontal and vertical planes, they inhibit non-uniform mass and stiffness distribution and are subjected to torsional forces. Studies in various Indian cities in hilly terrains have highlighted serious concerns about existing construction practices. Lack of adequate planning and design has resulted in haphazard development in hilly regions. This state-of-the-art review investigates the factors that influence the structural performance of buildings on slopes while explaining reasons that have caused enormous damages and even collapse of hill buildings in the recent earthquake events. The work discusses building configurations, comparison of various vital building regulations, the major problems encountered in building stocks and associated structural deficiencies on hill slopes. The significance of intensification of earthquake-related losses due to soil amplification has been well documented in the past. Insights from experimental and numerical studies focusing on impacts of topographical and geological factors on damage amplification of hillside buildings are fetched, the results of which are in good corroboration with the findings of post-earthquake surveys and reviews. This study establishes that a higher slope gradient necessitates more slope cutting than a lower slope gradient to get the same building footprint, and many times, this value exceeds the permissible height of slope cutting given in existing building byelaws. Such excessive slope cutting makes the slope weak and unstable. Recommendations and solutions to help enhance structural resilience, reduce disproportionate damages and mitigate failure of hill buildings have been delineated.