Probability Based Assessment of a Motorway Bridge in Denmark

Abstract

The paper presents the practical application of the Danish Road Directorate guideline for probabilistic assessment of bridges to an actual bridge structure, which failed to demonstrate sufficient load carrying capacity following deterministic assessment. The bridge, a post-tensioned box girder structure, was built in 1965. In addition to presentation of the safety classification of the structure the results of importance and sensitivity studies are presented which indicate the controlling variables. Following the assessment, bridge specific partial safety factors are calibrated for the critical limit state at the β-point which are compared with the global partial factors prescribed for deterministic assessment. It is important to point out that at no stage does the guideline compromise the safety of the structures presented, rather it provides a mechanism for determining their structure-specific safety for comparison with that deemed legally acceptable.