Reliability Analysis of Steel Building Frame Under Earthquake Forces

A simplified fragility analysis of steel building frame is presented which can be used for preliminary estimate of its probability of failure. The risk analysis procedure uses the format of probabilistic Risk Analysis (PRA) and considers band limited white noise at the bed rock as the seismic input. The steel building frame is modeled as a 2D frame and Pushover analysis is then carried out to obtain its capacity using SAP 2000. The response of the steel frame is obtained by response spectrum method of analysis for multi-degree of freedom system. The PRA includes uncertainties of the response due to variation of ground motion, material property, modeling & method of analysis and those of the capacity due to the variation of ductility factor and damage concentration effect. The proposed method of analysis is applied to a 5-storey steel building frame for obtaining its probability of failure using First Order Second Moment (FOSM) theory of the Reliability analysis. The fragility curves for the frame failure were generated for a number of parametric variations. The parameters include soil conditions, coefficient of variation of the uncertainty factors, ductility factor and soil amplification factor . The study shows that all the parameters considered in the study have considerable effect on the probability of failure. Keywords— Reliability analysis, First Order Second Moment (FOSM), White noise spectrum.