Reliability decomposition of dynamic wind load on structures

Abstract eng:
Multicorrelated stationary random process, such as wind pressure fluctuations on structures can be transformed into a set of subprocesses by diagonalizing their covariance matrix trough eigenvector decomposition. This eigenvector decomposition is known as the proper orthogonal decomposition (POD). The numerical advantage of the POD technique, akin to the modal analysis in structural dynamics, relies on the reduced-order representation through truncation of the higher eigenmodes associated with small eigenvalues. However, truncation of higher modes may not work effectively in the case of local response, which may lead to an underestimation of the local wind loads and their effects. In this paper a new method, called Reliability Decomposition, is proposed to overcome the weaknesses of the POD technique. In the proposed method the subprocess is selected based on the most probable load distribution at failure. This load distribution is obtained using first order reliability analysis. Since the Reliability Decomposition depends on the local effect under analysis, only one subprocess is needed in each case to obtain accurately results. In this paper, the methodology to obtain the load distribution to compute any internal force or displacement is presented. An example is developed to show the comparison among Reliability Decomposition and POD computations and results.

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