Effect of the Temperature on the Modal Properties of a Steel Railroad Bridge

The article is devoted to a study of the impact of various environmental conditions on modal parameters, such as natural frequencies and damping ratios. The modal analysis has been performed using the Stochastic Subspace Identification (SSI) method of measuring data every month on the same steel bridge structures located on an important railroad route from Prague (the Czech Republic) to Košice (Slovakia). The structure is approximately 60 m long, and the bearing structure is formed by two arch trusses. The bridge was exposed to ambient vibrations as well as to vibrations caused by a train passage. Accelerations and temperatures (the temperature of the air and the structure) were logged during the measurements. Natural frequencies were obtained from these acceleration data using the SSI method and processed into graphs of the dependencies between the natural frequencies and temperatures. Some statistical procedures were also applied.