Bounds on the Reliability of Structural Systems

by C. Allin Cornell,

Serial Information: Journal of the Structural Division, 1967, Vol. 93, Issue 1, Pg. 171-200

Document Type: Journal Paper


Most civil engineering structural problems are characterized not by a single random resistance subjected to a single random load, but by a complicated structural system exhibiting a number of mutually dependent modes acted on by a sequence of mutually dependent random loads. The task of determining the reliability of such a system under these conditions would be extremely difficult even if the necessary joint distribution functions were known. It is possible, however, to determine, with relative ease, bounds on the system reliability. One or the other of these bounds may also serve as an approximation to the desired reliability if the conditions leading to its derivation bold. In particular, it is likely that in many civil engineering situations the conditions are more nearly those of perfect dependence among modal failure events than perfect independence as is often assumed. In this case, a system reliability approximation is most readily obtained. The bounds are derived for general conditions of modal resistance and load distribution including time-dependent cases. The results prove valuable in a qualitative sense by showing the effect of such factors as number of modes, length of design life, and probabilistic dependence among modal resistances and among successive loads on the reliability of the system as a whole.

Subject Headings: Structural reliability | System reliability | Structural systems | Load and resistance factor design | Load distribution | Approximation methods | Live loads | Joints

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