This year marks the 40-th anniversary of Professor Andrzej Fabiszewski's death . He was a forerunner of the X-ray testing of butt welds in railway bridges in Poland. Professor Fabiszewski spent most of his life in Szczecin. The paper presents results of welded joint tests of 11 railway bridges located in the city of Szczecin. The results can be used for a new multi-level procedure of load-bearing capacity assessment of bridges in operation.

The long-term use of steel bridges leads to changes in the mechanical properties of their structural steels. This issue is demonstrated in a study of cast steels from four railway truss bridges built in 1875. The tests for each bridge involved an analysis of the chemical composition, determination of hardness and toughness, along with yield strength and ultimate strength. The tests made it possible to calculate the current mechanical properties of steels and to estimate their fracture toughness. One of the bridges in the study was built from low-carbon steel and the others from high-carbon steel, which was not thought to be used at that time.An assessment of the current mechanical properties of the steels allowed the bearing capacities of the bridges to be estimated and, following this, technical designs for their upgrading and repair to be drawn up.

StreszczenieNiepełne, a nieraz zróżnicowane przedstawianie wymagań normowych oraz ich mnogość jest w ostatnim okresie przyczyną różnej interpretacji tych samych zagadnień konstrukcyjnych. Podobny przypadek dotyczący połączeń spawanych podczas modernizacji dwóch mostów kolejowych przedstawiono w referacie.Słowa kluczowe: mosty stalowe, stal zlewna, spawalność stali AbstractLong lifespan of railway bridges causes technical and functional ageing of the structuresas well as the material degradation. Serviceability parameters of such structures are worsened and the structural steels are aging structurally. The problem is presented by results of research work on structural steels in two railway truss bridges.Many different code requirements and their complexity may cause different interpretations of the same structural issue. The similar case had happened for welded connections in retrofitting of the two railway bridges which are presented in the paper.

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