When carrying out seismic analysis of civil structures with a long service life, it is necessary correctly consider the damping of vibrations both in the ground and in reinforced concrete structures. When assigning damping parameters in reinforced concrete structures, it should be considered that under the influence of various temperature factors (during non-design work of civil structures) cracks appear in reinforced concrete elements, leading to an increase of damping compared to its normative values. It is possible to evaluate such damping in reinforced concrete using vibration diagnostics. In addition, for the correct assessment of building vibrations, it is important properly account damping in the ground, which is possible using the impedance method in accordance with ASCE 4-16 [1]. For this purpose, «ground» springs and dampers are used, simulate the stiffness and dissipative properties of the soil using the following formulas: K_eq= {K_х, K_y, K_z, K_φx, K_φy, K_φz} and C_eq= {C_х, C_y, C_z, C_φx, C_φy, C_φz} for components of equivalent stiffness and damping. The impedance method allows correctly simulate the soil in a dynamic problem and obtain a reliable seismic response of the building. The article presents methodology for evaluating parameters of damping associated with both the development of cracks in reinforced concrete and energy dissipation in the soil base. Recommendations are given for considering these parameters in the «soil-structure» system when analyzing seismic resistance of the building. The application of this technique in assessing the damping of a real building is demonstrated.

The purpose of the article is to develop a methodology for considering various sources of viscous damping in seismic analysis of civil structures, taking into account energy dissipation in the soil base and the development of cracks in reinforced concrete structures. Reliable accounting of damping in system will make it possible to specify the analysis of earthquake resistance of buildings, as well as the load on equipment.

Materials and methods. To assess energy outflow into the ground during vibrations of buildings, the following methods were used: the impedance method in accordance with ASCE 4-16 [1], the vibration diagnostics method for evaluating of damping in concrete, taking into account the development of cracks, and the method for evaluating damping in reinforced concrete by the width of the resonant amplitude. Next, we will consider the application of damping analysis techniques on the example of an industrial building.

This article presents a non-classical method of modal superposition for analysis of NPP building structures, taking into account springs and dampers that simulate soil. A description is given of a method that makes it possible to reliably take into account the "ground" damper, which makes it possible to significantly refine the results of dynamic analysis. The method has been certified by Rostekhnadzor and can be recommended for use in dynamic analysis of various buildings, with soil base.