Research on changes in properties of steel from the old road bridge

Abstract

This paper deals with problems stemming from the long service of steel bridges, in particular with the changes in the mechanical and strength properties of their steel over time. The considerations are of special relevance for bridges (including historic bridges) which have been in service for a long time, in the case of which it is vital to determine the actual operational strength of their main structural steel components. Operational load capacity reserves are evaluated as part of a technical condition assessment to determine the remaining service life.In this research an attempt was made to evaluate changes in the properties of the steel in the main girders of a heavily deteriorated steel road bridge (designated for dismantling) built in 1908. For this purpose tests were carried out on steel specimens taken from the most stressed places near the middle of a steel girder's span. The specimens were taken along the entire height of the girder's web. Analyses were carried out to determine whether the long service of the steel spans and their cyclic stressing resulted in changes in the properties of the steel and how significant the changes are.In order to reliably evaluate the changes laboratory chemical tests, metallographic examinations and strength tests were carried out on the structural steel. On the basis of the test results the changes in the properties of the steel as a function of time were determined. It was found which parameters were critical and to what degree.