Seismic resistance of frame-cladding buildings with a cold-formed galvanized steel profile framing

Building structural systems with light gauge steel framing technology are steadily gaining popularity due to their huge advantages over traditional technical solutions. As a result of the competitiveness inherent in LGSF technology, its application is gradually increasing in the manufacture of both bearing and nonbearing structures. At the same time, the actual absence of national standards for seismic design requires the development of programs and the implementation of research and development work to study the behavior of LGSF buildings in the conditions of seismic impact. The article touches upon the main problems of antiseismic construction of LGSF buildings and presents the results of domestic and foreign research.

Results of fundamental and applied seismological research in the Magadan region in 2016-2020

The results of fundamental and applied research, carried out by Magadan Branch of GS RAS during 2016-2020 in Magadan and Chukotka regions are presenting. Estimation of Seismic hazard of Russia’s Northeast (Magadan region) and seismic hazard maps for recurrence periods of 500, 1000 and 5000 years in scale close to that of detailed seismic zoning (DSZ) were made in cooperation with Institute of the Earth’s Physics RAS. In course of this work the estimation of initial seismic intensity and parameters of possible ground shaking in areas of critical facilities of Magadan region were made. For all of them a seismic micro zonation was carried out with methods of direct earthquake registration and comparing acoustic impedance. As result, a seismic amplification and intensity of seismic impact on the soils under main critical facilities were obtaining. The research results are shown on detailed seismic zoning maps that are basic for building projects of objects above.

Seismic stability of vibration-insulated turbine foundations depending on the frequency composition of seismic impact

The seismic resistance of vibration-insulated turbine foundations is a complex and multifaceted problem that includes many aspects. The turbine foundation is a special building structure that unites parts of the turbine and generator unit into a single machine and it is used for static and dynamic loads accommodation. The number of designed and constructed power plants in high seismic level areas is large and steadily growing. In addition, engineers and designers deal with the issue of the frequency composition of the seismic impact influence on the seismic resistance of vibration-insulated turbine foundations. Dynamic calculations were performed in Nastran software using time history analysis and the finite element method. The main criteria for the seismic resistance of a vibration-insulated turbine foundation are the values of the maximum seismic accelerations in the axial direction at the level of the turbine installation and the values of vibration-insulated foundation maximum seismic displacements (deformations of vibration isolators). The results of the calculation experiments proved a significant effect of seismic action frequency composition on the behavior of the vibration-insulated turbine foundations. Calculations of foundations, taking into account earthquakes of the same intensity, but with different values of the prevailing frequencies of the impact, lead to the differing by several times values of the maximum seismic accelerations at the turbine level and seismic displacements.

The Influence of the Friction-Sliding Coefficient of Support Structures and Parameters of Seismic Actions on Reactions and Reliability of Structures with Seismic Protection

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.

Assessment of the factors affecting slope stability in the southern part of the Sofia Kettle

A specific sample area was selected, where an assessment model was made for the stability of a slope subjected to anthropogenic impacts. A hillside slope zone from the foot of the Vitosha and Lozen mountains in the southern periphery of the Sofia Kettle was chosen as an exemplary area for a part of the hazards arising in the Trans-Balkan valleys. The anthropogenic impact on their slope stability was studied on three particular slopes. The study area is about 1.25 km2 and has a maximum distance of up to 3.80 km between the slopes. Landslide processes resulting from anthropogenic impact often occur on the territory of the Sofia Valley. The rise of construction, the development of hard-to-reach terrains with steep slopes, their undercutting, the seismic impact and the low values of the strength-deformation parameters of the geological varieties building up the respective terrains contribute to their occurrence. The deforestation, the loads with heavy embankments, the hydration and the inhomogeneity of the layers of the earth base have a strong destabilizing effect. The paper presents the results of field and laboratory tests and analyses of slope stability by the method of Fellenius. The severity of the impact of the various destabilizing factors was assessed.

Research into influence of drilling-and-blasting operations on the stability of the Kusmuryn open-pit sides in the Republic of Kazakhstan

Purpose. Research into influence of drilling-and-blasting operations on the nature of deformation in near-side masses of the design open-pit contours and assessing the seismic impact of blasting operations, which are the basis for development of recommendations on the rational parameters of drilling-and-blasting operations. Methods. The influence of drilling-and-blasting operations at the limiting contour of the Kusmuryn field is studied using the analysis of the mining-and-geological conditions and tectonics of the rocks constituing the field, in-situ surveying the state of the open-pit sides, analysis of the physical and mechanical properties of the host rocks, analytical studies and instrumental measurements of the blasting effect. Findings. Based on the analytical methods, the calculation and analysis of the seismic stability of the rocks at the field have been performed. By means of instrumental measurement of the blasting effect in open pit, data have been obtained on the seismic impact of blasting operations on the near-side masses. According to the results of these works, rational parameters of drilling-and-blasting operations at the limiting contour of the open pit have been determined. In addition, the main provisions for the organization of drilling-and-blasting operations at the limiting contour of the open pit have been developed. Originality. In this work, for the first time, a joint research method is applied, which includes an analytical calculation of the shock wave seismic impact on a rock mass, based on the results of which the dependency graphs have been obtained of the seismicity coefficient on the rock hardness coefficient at the Kusmuryn field according to the Protodyakonov scale for various explosives, as well as using the method of instrumental measurements, which serves to determine the seismic impact of an explosion on a rock mass. This makes it possible to substantiate the technology of conducting the drilling-and-blasting operations at the contour, providing a long-term stable position of the permanent side of the open pit. Practical implications. The results of the work will be used to calculate the safe parameters of conducting the blasting operations when placing the side in the final position at the Kusmuryn field. This research method can be applied at any mining enterprise conducting open-cut mining of minerals.

Dynamic Model of the VVER-1000 Reactor for Seismic and LB LOCA Evaluation

The assessment of seismic and dynamic strength for the VVER-1000 reactor with emphasis on fuel assemblies interaction is carried out based on experience for Ukrainian NPPs. Evaluation of fuel assembly structural response to externally applied forces is based on NUREG-800 “Standard Review Plan”, item 4.2 “Design of fuel systems”. The analysis considered two types of events: Safety Shutdown Earthquake (SSE) and Large break Loss Of Coolant Accident (LB LOCA). As LB LOCA for the VVER-1000 – “Maximum design accident” Recirculation Line Break is considered. For the analysis of the initial dynamics, the 3D CFD model (ANSYS CFX) of the VVER-1000 was adapted to account for the two-phase flow. To take into account the transience of the phase transition during depressurization, a special model of interphase exchange is proposed, which takes into account not only the nonequilibrium temperature, but also the features of the pressure change by analogy with cavitation. For full dynamic analysis, it is necessary to develop an analytical and/or FEM model of the reactor, which will include reactor elements, their masses stiffness and inertia characteristics. The developed model is validated against experimental data of natural frequencies of fuel assembles, for uncompressed and compressed working position, also with and without fluid influence. The seismic analysis consider the available response spectra for NPP site with 3-component seismic impact of SSE level. Another important issue is to analyze reactor elements interaction and in case of need, to account for the non-linear behavior of the model. The seismic and LOCA impact at the location of fixation of the fuel assemblies (lower and upper support plates) is calculated by taking into account the dynamic response of the reactor system as a whole. After demonstrating the seismic/dynamic stability of the fuel assemblies and the reactor internals, a justified conclusion is provided on preserving the safety factor for fuel assembles at both loadings.