The use of lifetime distributions in bridge maintenance and replacement modelling

This paper proposes a new method to determine lifetime distributions for concrete bridges and to compute the expected cost of maintaining and replacing a bridge stock. The uncertainty in the lifetime of a bridge can be represented with a Weibull distribution. It is recommended to fit this Weibull distribution on the basis of aggregating the lifetimes of demolished bridges (complete observations) and the ages of current bridges (right-censored observations). Using renewal theory, the future expected cost of replacing the bridge stock can then be determined while taking account of the current bridge ages and the corresponding uncertainties in the future replacement times. The same approach has been applied to the maintenance times of bridge elements. The proposed method is used to estimate the expected cost of maintaining and replacing the Dutch stock of concrete viaducts and bridges as a function of time.