# Mechanical Properties of Bridge Steel from the Late 19 th Century
## 3 Results  
### Main Mechanical Parameters  
The mechanical parameters of bridge steel were defined on the basis of a static tensile test, carried out at room temperature with the controlled increase in displacement. Test conditions were accordant with those specified in standard PN-EN 10002-1 + AC1 [26]. According to the standard, mechanical properties are defined using samples with a circular or rectangular cross-section. Tests were performed on samples taken from the structural girders of the bridge, by cutting them in two directions: longitudinal and transverse to the direction of rolling. Tests were performed using an MTS strength testing machine, via the process of controlled load application by the displacement of an actuated piston with the speed of 0.125 mm/s. The signal of displacement of the actuator, the force signal and the signal of elongation of extensometer, mounted on the measured section of the base sample of the length of 50 mm, were all recorded during the tests. Flat samples with a 10 \(\times\) 10 mm\({}^{2}\) working cross-section area were used for the definition of steel strength properties. The selection of such samples was dictated by the thickness of the plate cut out from the bridge section. The plate was 12 mm in thickness, and following its machining by milling and grinding, it was possible to obtain samples of a maximum thickness of 10 mm. A dozen pieces were extracted from the bridge for each longitudinal and transverse direction of rolling. They were tested in three different groups of specimens, but the results were very similar for the whole population. In order to ensure the most complete results, the group intended for a wide focus of research covering the mechanical, micro and macrostructural parameters is presented in this paper as representative. In fact, four samples were tested in this group to determine the mechanical parameters for each longitudinal and transverse direction of rolling. The [PERSON]'s statistical criterion was applied to reject atypical results from a population of four specimens and ensure a proper level of homogeneity in the results. The tests resulted in the definition of the main strength parameters of the bridge steel: upper \(R_{eH}\) and lower \(R_{eL}\) yield strength, ultimate tensile strength \(R_{m}\) as well as percentage elongation after fracture \(A\) and percentage reduction in area \(Z\). The defined parameters were determined on the basis of a population of \(n\) = 3 samples, individually for both longitudinal and transverse directions of rolling. A statistical analysis was performed to determine the mean values, standard deviation and confidence interval for the assumed significance level of 5%, for the obtained results. The achieved results can be observed in Table 1. As we can see, for the significance level of 5%, very low values of error bounds were identified. Figure 4 illustrates the typical \(\sigma\)-\(\epsilon\) stress-strain curves for samples cut out in longitudinal and transverse directions of rolling, respectively. Values of stress \(\sigma\) illustrated in the graphs were calculated as the quotient of the force value and the initial cross-section of sample \(S_{0}\). Values of strain \(\epsilon\) were obtained by dividing the recorded values of elongation  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Longitudinal Direction**} & \multicolumn{4}{c}{**Transverse Direction**} \\ \hline
**Parameter** & \(R_{eH}\) & \(R_{eL}\) & \(R_{m}\) & \(A\) & \(Z\) & \(R_{eH}\) & \(R_{eL}\) & \(R_{m}\) & \(A\) & \(Z\) \\  & **[MPa]** & **[MPa]** & **[MPa]** & **[\%]** & **[\%]** & **[MPa]** & **[MPa]** & **[MPa]** & **[\%]** & **[\%]** \\ \hline Mean value & 242.3 & 237.0 & 368.7 & 37.5 & 62.7 & 243.7 & 238.0 & 368.3 & 35.6 & 57.3 \\ Standard deviation & 1.53 & 3.00 & 1.53 & 0.50 & 0.96 & 3.79 & 1.00 & 1.53 & 1.22 & 1.15 \\ Error bound & 1.73 & 3.39 & 1.73 of the extensometer by its base length, \(L_{0}\).