Approaches to the models formation of seismic effects are proposed, taking into account the uncertainty and incompleteness extent of the initial seismological information. Earthquake-prone territories are divided into three types. The 1st degree uncertainty areas include territories where seismic effect parameters can be specified in the form of probabilistic distributions, the 2nd degree uncertainty areas include territories where effects parameters can be predicted at certain intervals. The 3rd uncertainty degree includes territories where all seismological information is expressed in terms of the intensities and repetitions given in the maps of the general seismic zoning of the Russian Federation territories (GSZ-93). The computational effects with varying extent of the seismological information uncertainty and the corresponding risk functions are determined.

The study is focused on a structure represented by a multimass elastic cantilever rod with dry friction seismic isolation elements in the support part under a horizontal random impact of a seismic type. The paper aims at investigating the seismic reaction and selecting optimal parameters of the seismic isolation system involving random impact characteristics, limit parameters of the structure, and the seismic isolation system. The researches are based on dynamic computations; the impacts and fluctuations of the system are random processes. The dynamic model of the structure with the considered seismic isolation is presented in the form of a cantilever rod with concentrated masses; a system of differential equations describing the displacement of the structure with the seismic-isolating sliding elements at the level of the top of the foundations is compiled; and a seismic impact is modeled in the form of a nonstationary random process. An algorithm is developed to integrate the system of differential equations of motion and to determine the statistical characteristics of the seismic reaction and reliability indicators of the structures with the seismic isolation. A method aimed at evaluating effectiveness of the seismic isolation system and selecting its rational parameters is suggested. We developed the computational dynamic model of the structure with the seismic-isolating sliding elements installed at the top level of the foundations, and elastic and rigid limiters for the movement of the sliding supports. This model is made in the form of a multimass cantilever rod that takes into account the relative movements of the masses and the stops of the system on the movement limiters. The structure’s movement under a seismic impact is described by a system of differential equations that takes into account the conditions of transitions of the structure from the state of sticking to the state of sliding and vice versa. The statistical characteristics of the seismic reaction and the reliability indicators of the structure in the process of vibrations are determined for different values of the maximum acceleration of the ground vibration, the prevailing period of impact, the number of masses in the calculated model and the coefficient of friction-sliding of the support elements. The influence of the impact parameters and the system on the efficiency of the seismic isolation of the structures with sliding elements is estimated. The proposed approach to selecting the optimal parameters of the seismic isolation system can be used as a research method aimed at improving efficiency of systems with different design options for seismic isolation of structures.

Objective. The purpose of these studies is to develop a methodology for assessing the seismic hazard of territories and a methodology for making an optimal design decision based on various criteria, including criteria for quantitative parameters of soil vibrations, taking into account regional peculiarities.Method. Estimation of quantitative parameters of seismic events registered on the territory of the Republic of Dagestan and adjacent areas by analytical and numerical methods. Determination of the reliability of buildings based on probabilistic models.Result. A method for estimating the parameters of soil vibrations based on the processing of instrumental records of known earthquakes, taking into account the characteristics of soils, is proposed. A method for making an optimal design decision is proposed, taking into account the parameters of soil vibrations and other target functions.Conclusion. The analysis of the obtained results showed that with an increase in the thickness of the loose layer, the magnitude of the maximum acceleration increases, the range of unstable fluctuations of the periods at the same time lies in the range of 0.1-0.5 seconds. The construction of buildings should be based on the parameters of the vibrations of the soils of the construction site, taking into account the lithological composition of the soil and other physical and mechanical properties.