Development Of Seismic Fragility Curve For Reinforced Concrete Buildings On Hill Slope

Abstract

In recent years, a large number of RC buildings are being constructed on hill slopes because of increased population density in cities like Kathmandu valley. With the lack of provisions for the construction of hill slope buildings on most of the seismic codes, it is more challenging to design and construct buildings on hill slopes, especially under seismic load. Buildings constructed on hill slopes pose both structural and constructional problems. At the time of earthquake, these buildings result in significant torsional response due to lateral loads. Therefore, these types of buildings must be carefully designed structurally, and careful supervision is necessary while in the construction phase. Also, it is vital to quantify the earthquake risk on such structures by vulnerability assessment for structural enhancements to minimize losses that could happen in near future due to seismic events. Hence, a study on the seismic vulnerability assessment of hill slope reinforced concrete frame buildings under earthquake excitations is needed. As a result, this study focuses on step back and step back setback buildings, and their vulnerability is assessed through the development of fragility curves, which will aid in taking necessary structural improvement action. Results obtained in this study are evaluated in terms of capacity displacement and demand displacement of the structures for the development of fragility curves. Since this study is mainly focused for Kathmandu valley, fragility curves obtained for various buildings are compared based on the seismic zone factor of Kathmandu which is 0.35g PGA. Depending on the results it is concluded that the vulnerability index of buildings increases as the number of storeys increases. It is also found that seismic vulnerability considerably increases with the increment of hill slope angle. Further, results show that the step-back setback buildings are less vulnerable than the step-back building and are generally preferred for construction.