As the bridge stock in The Netherlands and Europe is ageing, various methods to analyse the capacity of existing bridges are being studied. Proof load testing is one of the method to test the capacity of bridges by applying loads on the existing concrete bridges with small spans. Because of the fact that neither the actual traffic load nor the design traffic load required by Eurocode can be directly applied on the target bridge in real-life proof load testing, an equivalent wheel load has to be applied instead. The magnitude and the location of the equivalent wheel load is determined in such a way that it generates the same magnitude of inner forces in the cross section. Such calculation is usually done by linear finite element analyses (FEA). Whereas, different bridges have different geometry such as length, width, thickness, skewness, number of spans and lanes etc. For each configuration, FEA has to be done first to determine the loading position. The main aim of this paper is to study the relation between bridge geometry and unfavourable loading positions. Based on that, a guidance tool is developed for the determination of the critical proof load testing locations for the practice. To achieve this goal, a Python script has been developed using the general purpose FEM platform DIANA FEA. The script enables the automatic generation and analysis of a bridge model with different geometries and loading conditions. By applying the Eurocode Load Model 1 (LM1) at variable locations, the most unfavourable loading positions for the proof load are obtained at the corresponding boundary conditions. The output of the study provides a convenient tool for future proof load testing.@en

The aging of the epoxy-paper insulation of an oil-impregnated transformer was studied through partial discharge analysis. Accelerated electrical aging tests were carried out on samples of transformers windings, with and without paper insulation. Partial discharge (PD) measurements according to standard IEC 60270 were performed periodically during aging, and partial discharge phase patterns were recorded throughout the aging test. Some representative PD phenomena were obtained from the experimental results. The evolution of typical PD patterns is reported until breakdown.@en

This investigation aims to perform a probabilistic prediction of the lifetime of epoxy resin insulation of transformer windings. To support the prediction, several accelerated electrical aging tests were conducted at different voltage levels on epoxy resin insulated transformer winding specimens. The lifetimes achieved from the tests show a ¿flat z-shaped¿ V-t (voltage vs. lifetime) curve and indicate the well known threshold stress effect. Since the operation stress is in the convex part of the V-t curve, the life exponent n was not predetermined, but estimated from a data pool obtained at the lowest voltage levels. As a result, the operation life and its confidence intervals were predicted from the breakdown data at these low voltage levels.@en