Assessment of the Numerical Methods for the Seismic Resilience of Built Structures in India

Earthquakes are a major threat in India owing to the large stock of vulnerable structures combined with high seismicity across the country. The damage survey of Bhuj earthquake (2001) gave impetus for analysing the correct hazard level for design of buildings in Gujarat state. The buildings in Ahmedabad city suffered severe damages to around 70 midrise buildings. The seismic actions on the structure are dynamic in nature and cause low-cyclic fatigue in the structural components leading to the loss of strength and stiffness in each loading cycle. The structural engineers require strong numerical techniques to simulate the behaviour of the structures to ascertain their safety. However, each earthquake does not follow the same pattern and have different characteristics in terms of the PGA, time-period, natural frequency, and the amplification. Hence, the consideration of local seismic hazard is important for the design or evaluation of the buildings for predictable performance and generate resilience in them. The aim is to evaluate the performance of a 15-storey building for the seismic design codes i.e., US, TEC, CEN and IS, to highlight the significance of the current state of knowledge. The building satisfies Life Safety (LS) performance criteria under the highest level earthquake and damage to non-structural components is seen for the moderate earthquakes (4–6 Mw). The inferences from the scenario assumed for the Ahmedabad city can be applied to the other cities in Gujarat where time history records are not available. Resilience benchmarks shall be included in building byelaws to make it a legal obligation. Also, a model is proposed for design that shall be included in code books for multiple earthquake events (4–8 Mw).