Evaluation of proof load magnitudes for the assessment of bridges carrying special transports

Proof loading, to experimentally prove sufficient load bearing capacity of existing bridges where traditional estimation methods fail, has gained increasing research interest in recent years. In a proof load test, the bridge is loaded to a predefined magnitude determined such that, if reached without collapse, the desired reliability of the bridge to withstand actual traffic or the relevant load model is directly proven. This load magnitude depends on the traffic and load models adopted by the particular country as well as its approach to special transport management. This paper proposes a methodology for determining proof load magnitudes for short span bridges using the Danish classification system. Special transports, modelled by Danish standard vehicles, and ordinary traffic, based on Weigh-In-Motion (WIM) data, are simulated crossing a bridge. The results are a set of load magnitudes and configurations which can be used to proof load test and classify Danish bridges of different spans. Notably, for very short bridges the research showed that ordinary, but misloaded, traffic led to higher load effects than special transports. This finding may suggest that the current Danish practice of assessing existing bridges with the traffic load taken as the standard vehicle alone may be insufficient.