Evaluation of ground motion parameters and seismic response of reinforced concrete buildings from the Mw 6.9, 2011 Sikkim earthquake
Faisal Mehraj Wani, Jayaprakash Vemuri, Chenna Rajaram
Abstract
The continuous collision of the Eurasian plate and the Indian plate has resulted in several earthquakes in the Himalayan region. The 6.9 Mw 2011 Sikkim earthquake, which caused immense damage to the built environment in Sikkim, was triggered by an intraplate source on the overriding Eurasian plate. Strong ground motions from the earthquake were recorded at stations established by IIT Roorkee as part of the PESMOS program. In this paper, two near-field and eleven far-field ground motions from this earthquake are analyzed to evaluate their key characteristics and also to examine their time-frequency characteristics using Fast Fourier Transforms (FFTs). A comparison between the ground motion parameters of near-field and far-field seismic waves is performed and the distinct characteristics of both near-field and far-field ground motions are examined. Moreover, the impact of near-field and far-field ground motions on the seismic response of a code-compliant RC building is investigated. The results from the non-linear time history analyses indicate that the roof displacements and also the strain induced in the frame elements are less than the code-prescribed maximum limits. Further, the demand and capacity levels for the RC frame elements were evaluated to compute the performance ratios. The results indicate that the extensive damage to reinforced concrete buildings in the 2011 Sikkim quake was primarily due to the non-engineered nature of the structures and also due to the non-compliance of the built structures to the seismic design code provisions.