PSI - Issue 36

Mykhailo Hud et al. / Procedia Structural Integrity 36 (2022) 87–91 Mykhailo Hud, Natalia Chornomaz, Roman Grytseliak et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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the natural frequencies and periods of oscillation of the designed grain leg tower by Bardell et al (1997, 1998). The breakdown of the load-bearing structures of the grain leg tower will be especially noticeable during extensive natural disasters by Avramov et al (2007). The aim of the work is to evaluate the influence of the joint work of the foundation slab with the spatial structure of the grain leg tower on the frequencies and shapes of the natural oscillations of the grain leg tower. This goal is determined by the need to solve problems of assessing the stability and fatigue strength of the grain leg tower under the action of seismic loads. The finite element method (FEM) was used to investigate the influence of the joint work of the foundation slab and the grain leg tower, taking into account the engineering and geological conditions of the construction site on the frequencies and shapes of the natural linear oscillations of the grain leg tower by Kandasamy (2006), Najafizadeh (2009), Pellicano (2007), Pradyumna (2008). Modeling of a grain leg tower. Autodesk Revit software, which is based on the use of the finite element method (FEM), was used for geometric modeling by Singh (1998), Tornabene (2009). 2. Modeling To determine the frequencies and forms (modes) of natural oscillations of the structure used modal analysis in the software package "LIRA". Modal analysis is the first step for other types of dynamic analysis, such as analysis of transients, harmonic and spectral analysis. Modal analysis assumes that the system is linear. Other types of nonlinearity, such as nonlinear behavior of the material, contact boundary conditions, finite displacements - are neglected by Iasnii (2020), Xie (2021), Yasniy (2020). The finite element model of the grain leg tower was created in Cartesian coordinates (Fig. 1).

Fig. 1. Finite element rod model of the grain leg tower

The grain leg tower is modeled with a height of 23 m, for braces and racks we used a profile pipe of 100x100x4 mm made of S 235 steel. Young's modulus E = 206 GPa, Poisson's ratio ν = 0.3. To determine the impact of the foundation slab and engineering-geological conditions, the grain leg tower was calculated in two ways. In the first - the work of the foundations is simulated by rigid clamping of the supporting nodes of the grain leg tower, in the second – created a foundation slab with specified coefficients of soil hardness, corresponding to loam. The thickness of foundation slab is t = 300 mm, concrete class - C16/20. Seismicity magnitude of the construction site – 6,0. 2.1 Research results From the results of calculations (a sample from the first 6 modes) of natural frequencies (Table 1) it is noticeable that the tower in two versions of the simulation has multiple natural frequencies, which is typical for structures with axial symmetry. It should be noted that the natural frequencies in the second method of calculation are lower, which is a consequence of taking into account the joint work of the foundation-soil system.