Assessment of reliability of aging reinforced concrete structures

Aggressive environment and in-service loading can cause the resistance degr adation of existing reinforced concrete structures. They must be considered for the safety evaluation and service-life prediction of deteriorating str uctures. This paper presents an integrated approach for time-dependent syst em reliability analysis considering the stochastic nature of load processes , uncertainties in strength, degradation initiation time, and strength degr adation mode. The approach takes into account the partial correlation among the failures of structural elements, which arises from the fact that eleme nts of a structural system are subjected to the same load processes and/or dependent on some common basic random variables. The approach is efficient, since it does not require simulation. Analysis results obtained by using t he proposed approach indicate that the reliability of series systems is rel atively insensitive to the correlation between the failure of structural el ements. However, the reliability of parallel system is highly sensitive to the correlation. The use of the time-dependent reliability obtained by negl ecting possible correlation as a safety measure, therefore, should be avoid ed.