Reliability-Based Proof Load Factors for Assessment of Bridges

Abstract

Advanced reliability assessment can be required when evaluating existing bridge structures through proof load testing. The target load of a proof load test typically requires input from resistance models; however, bridges with a low documentation level are often the most relevant for proof load testing, and resistance models thus involve significant uncertainties. This paper presents a different approach to proof loading and target proof load, in which the resistance model is not included in the determination of this load. Instead, the target proof load is determined based on load models coupled to the desired target failure probability, thus ensuring sufficient safety of the existing bridge. The method is in line with the proposal for a new Eurocode on assessment of existing structures and is deemed to be superior to existing approaches. An essential assumption of the method is that monitoring systems can identify stop criteria before irreversible damage occurs. The approach was applied in a case study, where an OT-slab bridge with a span of 6.5 m was proof-load-tested and reclassified for capacity upgrading of a road stretch in Denmark.

Level 3 Assessment of Highway Girder Deck Bridges according to the Italian Guidelines: Influence of Transverse Load Distribution

“…While periodic inspections are sufficient for low and medium-low CoA values, when the bridge has a medium or medium-high CoA, preliminary assessments are performed (Level 3). Based on the results of the preliminary evaluation, the managing entity decides whether a detailed evaluation of the bridge (Level 4) is necessary, which is mandatory in cases where the class of attention is high, providing recommendations for preventive measures and necessary interventions [5,6]. As known, a detailed assessment needs an in-depth knowledge of the structure derived from an in situ experimental testing campaign [7].…”