Finding the Distribution of Bridge Lifetime Load Effect by Predictive Likelihood

To assess the safety of an existing bridge, the loads to which it may be subject in its lifetime are required.
Statistical analysis is used to extrapolate a sample of load effect values from the simulation period to the
required design period. Complex statistical methods are often used and the end result is usually a single
value of characteristic load effect. Such a deterministic result is at odds with the underlying stochastic
nature of the problem. In this paper, predictive likelihood is shown to be a method by which the
distribution of the lifetime extreme load effect may be determined. A basic application to the prediction
of lifetime Gross vehicle Weight (GVW) is given. Results are also presented for some cases of bridge
loading, compared to a return period approach and important differences are identified. The implications
for the assessment of existing bridges are discussed.