ABSTRACT
For a highway operator, such as ASFiNAG, bridges are very important assets. Despite all regular maintenance measures, these structures are strongly subjected to ageing and degradation, because of their exposure. Thus, leading to high maintenance expenditures. The optimal time for rehabilitation is therefore a decisive factor in the cost and measure planning of an infrastructure operator.
To find this optimal point in time and condition, it is important to have a simple index-based method for declaring an accurate condition status. Often the input for the method is gained in the course of regular bridge inspections.
The aim of this paper is to determine condition and degradation (condition indices) by using objective indicators, like humidity, electrical resistivity, and corrosion potential. For the purpose of objectivity and the demand of an exact determination of the condition state, an overall performance index (CDI) is derived from the condition indices by using an analytic hierarchy process (AHP). The challenge of assessing corrosion relevant data – especially when doing this in an automated process – is the influence of many factors on the measurement values in unknown extent (e.g. concrete humidity on corrosion potentials), which doesn’t allow an explicit, fixed interpretation as it can be done with e.g. concrete strength data.
Hence, this assessment methodology is Fuzzy-Logic (FL), which treats and combines input data in not clear-cut borderlines to choose an optimal maintenance measure. A case study will proof the method to deal with lack of knowledge and uncertainty in this fuzzy decision process.
