Variations in the integral amplification of of seismic ground motions on the territory of Kiev

The relevance of the research and the results presented in the article is due to the need to provide the designers of seismic-resistant construction with maps of seismic zoning of settlements and agglomerations on the territory of Ukraine in the amplitude parameters of seismic ground motions. An analytical-empirical approach to mapping is proposed on the example of the territory of Kyiv, which can be implemented in conditions of an insufficient number of results of instrumental seismological observations. This approach gives positive results provided that the territory is well studied in geological terms. Within the territory of Kyiv, using the method of seismic-geological analogies, areas (taxonometric zones) have been identified that are homogeneous in response to seismic effects. For all taxonometric zones, seismic-geological models of the soil strata were built and their spectral characteristics were calculated taking into account the nonlinear deformation of the soil. The averaged frequency response was also calculated for the ground conditions of the territory of Kyiv as a function of the distribution of the average values of the spectral amplification of seismic oscillations in frequency for all zones. A map of the distribution of the deviation of the integral amplification of seismic vibrations from the average value for the territory of Kyiv was constructed. It is proposed to use a spectral amplification map to determine the values of the calculated relative ground acceleration of the investigated site when using the spectral method for calculating the emergency combination of loads taking into account the seismic effect. The map of the distribution of the deviation of the integral amplification of seismic oscillations from the average value for the territory of Kyiv is an intermediate stage in the construction of seismic zoning maps for Kyiv in amplitude terms of ground motions.

GEODYNAMICS

Purpose. The paper substantiates the need for building seismic zoning maps of Kyiv in the physical parameters of ground motions: peak ground accelerations (PGA), peak ground velocities (PGV) or peak ground displacements (PGD), which are the basis for the effective use of methods for calculating seismic loads on buildings, structures and individual responsible constructions. An intermediate stage in the creation of such maps is the development of a map of seismic zoning of the territory of Kyiv in terms of relative integral estimates of spectral increments in seismic soil oscillations, arising from the influence of the peculiarities of the distribution of physical parameters of soils. The intermediate map gives the distribution over the city territory of a quantitative assessment of the influence of the spectral characteristics of the soil on the seismic hazard, expressed in systemic physical quantities. Methodology. An analytical-empirical approach to mapping the seismic hazard of territories is applied. Within the territory of Kyiv, using the method of seismic-geological analogies, areas (taxonomic zones) were identified, where the seismic effect can differ significantly both in physical parameters: displacement, speed, acceleration – and the ability of soil strata to significantly affect the spectral characteristics of the soil. Results. For each taxonomic zone, a computational seismic-geological model with inelastic deformation parameters has been built, which makes it possible to take into account the occurrence of nonlinear effects under significant seismic influences. Equivalent linear modeling was used to calculate the frequency response of seismic-geological soil models for each taxonomic zone. The averaged frequency response for the ground conditions of the territory of Kyiv was calculated. A map of the distribution of the deviation of the integral amplification of seismic oscillations from the average value for the territory of Kyiv was built. The integral spectral amplification is the area of the subspectral function. A dynamic analysis of the propagation of seismic oscillations in seismic-geological models is carried out and the influence of the upper sedimentary layer on the value of the peak ground acceleration PGA on the free surface is illustrated. Originality. For the first time within the territory of Kyiv, areas (taxonomic zones) have been identified, where the response of the soil to the seismic effect will differ. A map of the distribution of the deviation of the integral amplification of seismic oscillations by soils from the average value for the territory of Kyiv was constructed. Practical significance. The map of seismic zoning of Kyiv in amplitude terms of soil oscillations is proposed to be used when applying the spectral method for calculating an emergency combination of loads, taking into account seismic effects, to determine the value of the calculated relative ground accelerations of the construction site under study.

Continual model and dynamic calculation of buildings under seismic impacts

Continuum plate model in the form of a cantilever anisotropic plate developed in the framework of the bimoment theory of plates describing seismic oscillations of buildings is proposed in this paper as a dynamic model of a building. Formulas for the reduced moduli of elasticity, shear and density of the plate model of a building are given. Longitudinal oscillations of a building are studied using the continuum plate and box-like models of the building with Finite Element Model. Numerical results are obtained in the form of graphs, followed by their analysis.

Hydropower Dam State and Its Foundation Soil Survey Using Industrial Seismic Oscillations

In this article, we suggest a new type of seismic source for surveying both structure state and foundation soil conditions regardless of the level of seismic noise. In our opinion, powerful industrial equipment can be treated as seismic sources. We describe the results of a survey conducted on the Song Tranh-2 hydropower dam located in Central Vietnam. After a М = 4.7 earthquake, the dam visual inspection revealed zones of the excessive durability loss: cracks and areas with an elevated infiltration of water into the dam galleries. Powerful industrial equipment generates continuous quasi-harmonic mechanical oscillations (seismic waves) that travel through layers of rocks. These seismic oscillations are recorded by receivers in different measurement points such as the dam body, abutments, and the foundation soils. Anomalous amplitudes of these oscillations indicate the presence of weakened zones in the structure or in foundation soil. We coupled passive and active seismic methods to more precisely find such zones. In this case, active seismic methods allowed us to investigate dam abutment zones, and passive seismic methods were used to localize weakened zones in the dam-foundation soil system. We assumed that the joint contribution of two factors was the cause of the dam weakening. One of them was caused by increased water infiltration through the rock mass and its contact zones, and the other was reservoir-induced seismicity contributing to the deterioration of the foundation soils, which was possibly the reason for a shift in the dam in the contact zone with the rock mass foundation. It is necessary to perform computer modelling, which was not included in our research. The developed method can be used for the safety control of the hydropower station dams.

Study of longitudinal oscillations of a five-storey building on the basis of plate continuum model

Continuum plate model in the form of a cantilever anisotropic plate developed in the framework of the bimoment theory of plates describing seismic oscillations of buildings is proposed in this paper as a dynamic model of a building. Formulas for the reduced moduli of elasticity, shear and density of the plate model of a building are given. Longitudinal oscillations of a building are studied using the continuum plate and box-like models of the building with Finite Element Model. Numerical results are obtained in the form of graphs, followed by their analysis.

STANDING WAVES IN ENGINEERING OBJECTS OF COMPLEX CONSTRUCTIONS

According to the results of research on complex engineering objects, results were obtained that demonstrate significant deviations from the models of buildings and structures adopted as the basis for calculating seismic resistance and structural stability. First, it is the existence of reflecting seismic oscillations of the boundaries inside the building, when standing waves form a common field for the building as a whole and a local field for a part of the object. Secondly, a block structure of the object, when there are natural oscillations of different magnification with a different area of the object's coverage, when some blocks independently oscillate, they unite into one system. Thirdly, the existence of walls with double reflecting properties, which changes the field of standing waves. Fourthly, the complex geometry of the object causes fields of standing waves, e is described by two wave numbers. Experimental data show that in the theory of buildings, it is necessary to move to the models of nested resonators, models of coupled resonators, and the verification of models should be entrusted to the standing wave method.

Traces of the strong earthquakes in ancient Mikhaylovka archeological monument, Kerch’ Peninsula, Crimea

In the paper there are results of archeoseismological study of an antic archeological monument – Mikhaylovka hill-fort located in Kerch’ peninsula. Studied deformations complex includes: systematic tilts, shifts and collapses of building constructions of latitudinal strike northward. Building elements of longitudinal strike tilted, shifted and collapsed westward. We revealed one counterclockwise rotation in a wall part which was not anchored. Most impressive and unique is shearing and shifting southward of a significant fragment of northern city wall. The revealed deformations in the trench No. III of Mikhaylovka hill-fort undoubtedly demonstrate their seismogenic origin. Large number of double walls – original walls and counterforce ones – “krepida’s” testifies on at least two events of destruction and deformation in Mikhaylovka fort-hill. Local seismic intensity was apparently (VIII) ≤ Io ≤ IX. According to numismatic founds and fire traces first earthquake occurred in beginning of II century AD, second earthquake - in III century AD. Maximum summary seismic oscillations during first earthquakes propagated apparently in latitudinal direction which led to wedging of significant part of the northern wall of the hill-fort. Seismic shocks during second earthquakes went along NNW-SSE axis. This direction is testified be systematic character of tilts, shifts and collapses of the walls of both directions.

Numerical Analysis of the Exact Solution of the Wave Equation of the Longitudinal Seismic Oscillations of Soil and the Construction as a Point Insertion

The numerical analysis of the exact solution of the system of the differential equations which includes the partial differential equation of the longitudinal seismic oscillations of the soil and the ordinary differential equation of oscillations of the construction in the form of a point rigid insertion.