Probabilistic load determination

Abstract

This paper deals with a probabilistic approach of the hydraulic loading conditions of the Oosterschelde storm surge barrier. The joint probability density function of the hydraulic boundary conditions (storm surge level , wave energy and water level at the Oosterschelde basin) is used as input. By introducing linear spectral transfer functions between the load and the hydraulic parameters , this density function can be transformed into the two-dimensional probability density function of wave- and static loads from which the probability distribution of the total hydraulic load can be derived by integration.

The needed transfer functions were determined with the aid of a mathematical model, which has been checkedb y a series of hydraulic model tests. By applying a probabilistic load determination as indicated above, the total horizontal load at the storm surge barrier was reduced by approximately 40%, as compared to the rather pessimistic outcome of a deterministic load determination, in which all unfavourable and unlikely events are assumed to coincide. The probabilistic load determination has also been used in a probabilistic approach of the behaviour of the storm surge barrier, in which the structural properties were treated as random variables, in addition to the loads. In this way, a risk analysis has been executed to find the failure probabilities of several parts of the barrier, which have to be in balance.