CORRELATION EFFECTS IN THE RELIABILITY ANALYSIS OF PARALLEL STRUCTURES

For the reliability assessment of structures which may fail in one of several failure modes, bounds on the probability of failure of the structure have been developed. It is well known that even the best of these bounds are dependent on the correlation between the failure modes and that this correlation is, in turn, dependent on the correlation between member properties. Relatively little appears to be known about the importance of member property correlation effects in reliability analysis, nor about the actual values of correlation coefficients. Before attempts are made to increase our knowledge of member correlation, the importance of correlation effects in structural reliability calculations should be assessed. A simple study of the sensitivity of structural reliability assessments to variations in correlation coefficients for parallel structures is described. It is demonstrated that the structural reliability for the structure considered is sensitive mainly to correlation between different locations within the same member or related members. (TRRL)