RAPID ESTIMATION OF FRAGILITY CURVESUSING ENDURANCE TIME METHOD

Randomness of earthquakes’ inherent causes scattering of structural responses. The most complex analytical methods such as risk, hazard and performance based design try to estimate seismic responses properly. Most of the time, damage probability of structures are studied using fragility curves. Multi-strip analysis (MSA) and incremental dynamic analysis (IDA) are the most dynamic analysis methods which evaluate seismic responses in different intensity measures (IMs). Numerous nonlinear dynamic analyses needed in mentioned methods to evaluate response distributions lead to complexity and time consuming process of them. Endurance time analysis (ETA) evaluates structural responses in different IMs by using artificial intensifying acceleration functions with least dynamic analysis. In this paper a new approach has been suggested to obtain fragility curves rapidly using ETA. Hence, the capability of ETA is evaluated to determine fragility carves by making use of equivalent SDOF instead of MDOF system. Results show that ETA method applied to an equivalent SDOF system predicts MSA fragility curves obtained by analysing a MDOF system with appropriate accuracy, by applying an uncertainty factor of 0.6 to lognormal standard deviation of ETA method.This approach reduces hugecomputational efforts and consumed timewhich are spent on the otherproccesswith a neglecting tolerance.