Uncertainty in seismic analysis and design

A novel seismic analysis and design procedure under uncertainty is proposed. The catastrophic damage caused by recent earthquakes prompted the study. A stochastic finite element-based hybrid approach is proposed to evaluate the reliability of complicated real structures considering all major sources of uncertainty and nonlinearity. The algorithm rationally and effectively combines the concepts of the response surface method, the finite element method, the first-order reliability method, and the iterative linear interpolation scheme. The unique feature of the technique is that the seismic loading can be applied in the time domain, providing an alternative to the classical random vibration approach. The algorithm was elaborated by evaluating the probabilities of failure of braced and unbraced steel frames. Several design implications were identified. The information on the probability of failure can be used in the risk-consistent performance-based seismic design guidelines being developed by many countries. The selection of member sizes and arrangements as well as performance requirements can be established with the help of the proposed algorithm. This is very advanced reliability analysis technique for seismic loading applied in time domain explicitly considering the uncertainty associated with it. In the analysis and design of structures, uncertainty in seismic loading should not be overlooked.