RELTSYS: A computer program for life prediction of deteriorating systems

As time-variant reliability approaches become increasingly used for service life prediction of the aging infrastructure, the demand for computer solut ion methods continues to increase. Effcient computer techniques have become well established for the reliability analysis of structural systems. Thus far, however, this is largely limited to time-invariant reliability problem s. Therefore, the requirements for time-variant reliability prediction of d eteriorating structural systems under time-variant loads have remained inco mplete. This study presents a computer program for RELiability of Time-Vari ant SYStems, RELTSYS. This program uses a combined technique of adaptive im portance sampling, numerical integration, and fault tree analysis to comput e time-variant reliabilities of individual components and systems. Time-inv ariant quantities are generated using Monte Carlo simulation, whereas time- variant quantities are evaluated using numerical integration. Load distribu tion and post-failure redistribution are considered using fault tree analys is. The strengths and limitations of RELTSYS are presented via a numerical example.