On the dependency between optimal redundancy and optimal inspection of structural systems

Conventional Structural Reliability (SR) theory states that (gross) errors in design, construction, operation, inspection and maintenance of structural systems should be handled by quality control.Yet, quality control is imperfect; hence, some (gross) errors still pass the checking, imposing a significant impact on structural safety.This article presents a simple model to illustrate the dependency between optimal system redundancy and the optimal frequency of inspections.The work addresses the risk-based optimization of Daniels Systems of components, which are inspected times over a specified lifetime.A latent hazard rate is employed to model the arrival rate of system damage affecting a single element.If system damage is not detected before the next scheduled inspection, the damaged system is exposed to the arrival of load pulses.Fragile and ductile material models are considered.Results show a strong dependency between the optimal number of components (system redundancy) and the optimal number of inspections.As increases, both and increase.Yet, results are also largely influenced by the correlation between the strength of the elements of the Daniels system, and by the variance of material strength.The study shows that the latent hazard rate is a link between structural reliability theory and quality control.