THE USE OF LIFETIME DISTRIBUTIONS IN BRIDGE REPLACEMENT MODELLING

Abstract

This paper proposes a new method to determine lifetime distributions for concrete bridges and to compute the expected cost of replacing a bridge stock. The uncer- tainty in the lifetime of a bridge can best 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 easily determined while taking account of the current bridge ages and the cor- responding uncertainties in the future replacement times. The proposed methodology is used to estimate the cost of replacing the Dutch stock of concrete bridges as a function of time.