RELIABILITY OF MDOF-SYSTEMS

To estimate the safety and reliability of nonlinear structural (MDOF)-systems subjected to random dynamic loading the response surface methodology (RSM) and Monte Carlo Simulation (MCS) respectively appear to be the most general approaches to calculate the failure probabilities of such systems. In an effort to reduce the number of computational time consuming simulations as generally required for direct MCS, only a small part of which is important for the assessment of failure rates, a new selective MCS technique named 'Double and Clump' (D&C) is suggested. The main idea of this procedure is to increase for each time step the relatively low number of response samples containing higher mechanical energy. The selective MCS procedure is tested by analysing nonlinear SDOF oscillators, for which exact analytical solutions exist. A good agreement between the distributions F(x) in the tails is obtained covering a wider range, i.e. 10(-7) < F(x) < 1.0-10(-7). The efficiency of selective MCS is demonstrated by applying it to a six-storey frame structure subjected to earthquake excitation. A comparison with results obtained by using the RSM is presented and discussed.