Non-linear soil-structure interaction analysis of railway bridge subjected to earthquake ground motions considering different types of soil

Abstract

In this paper, the dynamic behaviour of an existing multi-span railway bridge in Afyon (Turkey) under different earthquake ground motions considering soil-structure interaction (SSI) is investigated. A Two-dimensional (2D) finite element model of the railway bridge-soil system was established and a 2D version of the PLAXIS FEM package has been performed in numerical analysis. Considering the soil property of the bridge site, the analysis was performed for three types of soil; the soils were specified as soft, medium and stiff. Three types of earthquakes including Kocaeli (Turkey, 1999), Kobe (Japan, 1995) and Manjil (Iran, 1990) earthquakes are defined as input motions. According to the result of the dynamic analysis, the dynamic responses of the railway bridge including the horizontal and vertical displacements of the top of the railway bridge (point A), base point of the bridge (point B) and soil level (point C) are calculated by the PLAXIS program and showed as graphic form. The obtained displacement values are different for each kind of earthquake ground motion; hence, it means that the bridge structure and soil have different responses to each kind of earthquake ground motion. The displacements obtained by the Kocaeli earthquake are compared with the results obtained by Kobe and Manjil earthquakes. The analysis with PLAXIS demonstrated that for different conditions delimitation, distribution of travel and the fundamental frequency for each soil type change according to its mechanical properties. The obtained results show that the phenomenon of structural soil interaction must consider in the bridge analysis and also demonstrates that the proximity of the fundamental frequencies of the structure and soil strongly influences on soil-structure interaction.