Stop criteria for proof loading: The use of stop criteria for a safe use of ’Smart Proof loading’

Many bridges in The Netherlands are built around 1960-1970 and currently reach their designed service life of 50 years. The traffic loads are increasing and new insights in the behaviour of constructions are obtained. Therefore there are doubts about safety of these bridges and viaducts and these must be assessed. As the current safety codes have changed over the years, not all structures fulfil the current safety requirements, however replacement of the bridges brings undesirable high cost with it. Therefore alternative ways are sought to demonstrate the safety requirements. One way to do so is by proof loading, during which the structure is loaded in a controlled way. During proof loading stop criteria are used, which are measurable parameters that indicate the condition of the structure during the proof loading test. Reaching the predetermined value(s) of one or more stop criteria could lead or leads to abortion of the test, otherwise undesirable and irreversible damage of the structure or even failure might occur.