|
The mechanical and microstructural properties as well as durability of more than century-oldsteel railway bridges that are still widely in use, among others in Poland, have not been wellrecognized. Ignoring the effect of material and mechanical properties on the operation of an old-steel bridge may eventually lead to the structure’s failure. This study investigates the reliability ofa 100-year-old bridge made of wrought (puddled) iron. The aim of this study is to identify themicrostructural and mechanical properties of over century-old steel bridge components in rela-tion to the requirements for modern mild steel grades. The paper presents an analysis of thematerial and mechanical behaviour of a truss railway bridge that had been in operation for over acentury. Laboratory tests were performed on samples taken from the component parts of a dis-mantled railway bridge, i.e. stringers, crossbars, lower belts, stringer bracings and wind bracing.Fatigue, fracture, hardness and tensile tests are performed to estimate the mechanical propertiesof the investigated steel bridge component parts. Spectroscopy is used to examine the chemicalcomposition of every element. Light optical microscopy and scanning electron microscopy areemployed to examine the microstructure of the steel component parts and its non-uniformities.Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) are used toobtain data about the fracture mechanism and the chemical composition of non-metallic inclu-sions. Microstructural and mechanical results are discussed in relation to modern mild steelgrades S355 and S235, which are widely used structural ferrous alloys. Based on the chemicalcomposition analysis, the possibilities of increasing the strength of the bridge by weldingmethods and the application of fibre-reinforced polymer (FRP) composite materials are dis-cussed. Obtained results add to the body of knowledge about the maintenance, reinforcement anddemolition of bridge structures, which is crucial for preventing failure of over 100-year-old steelstructures. This research is an introduction to the study on reinforcing old steel structures by FRPcomposite materials.
|
