Seismic Fragility Assessment of Low Rise RCC and Steel Frame Buildings Founded on Soft Soil of Langol, Manipur

This paper presents comparison and quantification of seismic responses in cases of typical low-rise steel and reinforced concrete buildings standing on soft soil of Langol (high seismic zone), considering both rigid-base and realistic soil-base conditions. The foundation design incorporate local geotechnical conditions with settlement corrections. In-elastic time history analysis is performed on the building models considering tested data set of Langol multi layered soil profile parameters. Results show that the influence of soil-structure interaction significantly increases inter-storey drifts, particularly in the steel buildings. While, the reinforced concrete buildings show better seismic resistance. Fragility analysis are conducted to derive the probability of damage to structures under varying seismic intensity measure. Comparing to the conventional fixed based condition, the probability of damage thresholds for the reinforced concrete and steel building increase to ranges of 25% − 44% and 35–47% respectively. The results underscore the necessity to consider realistic soil-base in earthquake resistant design of structures founded on soft soils and highlight the benefits of reinforced cement concrete frames building over steel frame buildings founded on similar geotechnical conditions.