How does the physical structure deteriorate
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Structural deterioration of infrastructure systems is a serious concern because it might decrease the lifespan and reliability of the systems. In addition, the prediction of structural deterioration can be helpful in optimizing design of infrastructure systems accounting for their life cycle. In particular, with the advent of performance-based engineering methodology, models to predict life-cycle performance of infrastructure systems are needed. In this chapter, deterioration in a typical RC highway bridge bent subject to earthquakes and corrosion of reinforcement is modeled. For this purpose we used a stochastic formulation that combines shock deterioration due to earthquakes and gradual deterioration due to corrosion. Three deterioration mechanisms are focused upon: loss of lateral stiffness of the bridge columns due to earthquakes, loss of lateral stiffness of the bridge columns due to corrosion, and loss of deformation capacity due to corrosion and low-cycle fatigue of longitudinal reinforcement.
The results show that deterioration due to corrosion of reinforcement and seismic stiffness deterioration have a significant effect of the lifespan of the bridge bent. The effect of low-cycle fatigue damage is found to be insignificant on the expected lifespan of the bridge bent. The results also show that it is important to study the combined effect of corrosion and seismic damage. The obtained results are specific for the scenarios that are similar to the analyzed one (i.e., type of bent, regional seismicity, and corrosive environment) and thus observations/conclusions made in this study should not be directly extended to other deterioration scenarios. Infrastructure systems are complex systems and modeling their life cycle in the presence of multiple sophisticated and interacting deterioration processes is highly challenging. However, the benefits of continuing research in this area are also considerable. In order to advance the state-of-the-art, work is required to model the interaction between various deterioration mechanisms, modeling non stationary deterioration processes and developing robust frameworks to incorporate laboratory data in the models.