# Mechanical Properties of Bridge Steel from the Late 19 th Century
## 1 Introduction  
Concrete, steel, wood and masonry are still the most popular materials used in the field of structural engineering. Compared to these, modern structural steel is a relatively new material, as its use in construction effectively dates back only to the 19 th century, when the technology of its production was developed. At that time, due to its high and favourable strength parameters, steel had relatively quickly become the main structural material and was used for the construction of many large-scale structures. Metallic materials, such as iron and then steel, were used relatively early on a wider scale for the construction of bridges. This was due to the demand for the construction of railways during the industrial revolution, which began in England in the 18 th century. Iron Bridge, built in 1779 using cast iron elements and opened on 1 January 1781 in Ironbridge in England, is the world's first bridge made of materials other than wood and stone. This year may, therefore, be considered as the beginning of modern bridge construction. During the following period, bridge structures were built using puddled and cast steel, as a result of the modernisation of the technology of their production. From the late 18 th century, cast iron, and then steel bridges and viaducts were also built on the territory of today's Poland, which was then under partitions until 1918. Many of these structures built in the 19 th century still exist and are still in operation. Although steel structures which are now historic are relatively recent when compared, for example, to ancient structures, due to the properties of this material, they require preservation, and sometimes repair or reinforcement. This is necessary due to the occurrence of ageing processes of steel used for the construction of elements of building structures, which is exposed to various influences for many years during its operation. Degradation processes which affect the structure of structural steel in this case result in the reduction in the values of its mechanical parameters. In the case of steel structures, significant reduction in the strength of steel may result in the decrease in their load-carrying capacity. When this is the case, the load-carrying capacity of such structures is reduced, and may even be insufficient for safe operation. Structures built in the 19 th century have now been in operation for over 100 years, and many of them are still used in many countries around the world, including Poland. Therelevant requirements are currently defined by standard EN 1990 [1], which states that the maximum operational life of bridge structures should be a minimum of 100 years. There are a number of factors that significantly reduce the durability of bridges [2]. This is why new solutions are constantly being sought after that will increase the operational life of bridges. In addition, it should be noted that integral bridges are among the modern constructions which meet these expectations [3; 4; 5]. In reference to old bridges exposed to multiple hazards, mostly due to material degradation processes, it is necessary to carry out tests of the strength of various types of structural steel used since the 19 th century. Upon the determination of actual strength parameters of the material, it is then possible to evaluate the load-carrying capacity of structures built in this period, and to verify their operational safety on the basis of existing standards. It should be noted that the above works are undertaken in many countries around the world [6; 7; 8; 9; 10; 11; 12; 13; 14; 15]--e.g., Poland [16; 17; 18; 19; 20; 21; 22]. Studies of various material properties of old steels extracted from the engineering structures other than bridges, are also very helpful in such analyses [23]. This article presents the results for tests performed on steel taken from a bridge built in the late 19 th century in Poland--a structure which has been in operation for over one hundred years. It presents the main mechanical parameters of the tested steel and its macrostructure.