"Вестник МГСУ"

Application of accelerograms to the analysis of structures, exposed to seismic loads, and generation of synthetic accelerograms may only be implemented if their varied characteristics are available. The wavelet analysis may serve as a method for identification of the above characteristics. The wavelet analysis is an effective tool for identification of versatile regularities of signals. Wavelets can be used to detect inflection points, extremes, etc. Also, wavelets can be used to filter signals.The authors discuss particular theoretical principles of the wavelet analysis and the multiresolution analysis. The authors present formulas designated for the practical application. The authors implemented a wavelet transform in respect of a specific accelerogram.The recording of the horizontal component (N00E) of the Spitak earthquake (Armenia, 1988) was exposed to the analysis as an accelerogram. An accelerogram was considered as a non-stationary random process in the course of its decomposition into the envelope and the non-stationary part. This non-stationary random process was presented as a multiplication envelope of a stationary random process. Parameters of exposure of a construction site to the seismic impact can be used to synthesize accelerograms.

The article focuses on the problem of calculating seismic impact on structures. The article studies the impact of structures on the changes in seismic load parameters. Studies are conducted with the use of direct dynamic calculation methods implementing explicit integration schemes equations of motion. Two computational models of monolithic reinforced concrete buildings on elastic half-space are considered: 9 and 16 storeys. The solution of the problem is found in time domain by direct integration of the equations of motion for the explicit scheme using software package LS-DYNA. The foundation simulation is performed using solid finite elements, and the bearing structures of buildings — using solid shell finite elements. The external action applied in the horizontal direction X is shown by accelerogram. Synthesized accelerogram is obtained by the Institute of Physics of the Earth of the Russian Academy of Sciences for Imereti lowland region, city of Sochi. In the study the authors used a specially developed method of calculation based on the algorithm of the base-structure interaction (interface soil-structure interaction). This algorithm can effectively simulate the interaction with linear and nonlinear deformable half-space in the form of a limited array with "transparent" borders. The results show that neglecting the change in external seismic impact parameters caused by the influence of the structures leads to errors in calculation results, which in turn can lead to deficiency of the bearing capacity and seismic resistance of building structures designed in seismic regions. When using the accepted methods of earthquake calculation based on existing regulations, the original design accelerograms should be set considering the dynamic characteristics of the designed buildings.

Earthquakes can be very strong and can lead to significant damages. Effect of earthquakes depend on seismic action characteristics (intensity, spectral composition, etc.), foundation soil properties in region of construction, design and construction quality. In seismically dangerous regions structural calculations the current design standards suppose the use of the coefficient K1, which takes account the non-linear work of construction material and the allowable damages of structures. Our research shows that a stiffening core fails in case of intensive earthquake if the walls are designed according to current design standards. Thus, plastic deformations do not occur and develop in the supporting elements at the beginning of the process, so the lowering coefficient K1 should be disregarded. As stiffening core is projected with account for the reduction factor K1, the existing reinforcement is not enough for standing the emerging stress and its failure happens followed by a redistribution of the stress to frame columns. The columns are also projected with account for the reduction factor K1 and are not able to take such an increase stress beyond design. There is destruction of column frame and complete collapse of the building. So seismic resistance of bearing structures is reduced several times. The approach to estimating K1 must be responsible, based on the latest scientific research, which sometimes could not be done according to the acting design standards.

An earthquake is a rapid highly nonlinear process. In effective normative documents there is a coefficient K1, which takes into account limit damage of building structures, i.e. non-linear work of building materials and structures during seismic load. Its value depends on the building constructive layout. However, because of the development of construction and new constructive solutions this coefficient should be defined according to design-basis justification. The article considers the five-storey building calculation on seismic impact by linear-spectral and direct dynamic methods. Our research shows that the coefficient K1 for this building is 0.4, which was calculated using nonlinear dynamic method. According to effective normative documents K1 is 0.25…0.3 for buildings of this type. Thus we get a lack of seismic stability of bearing structures by 1.5…2 times. In order to ensure the seismic safety of buildings and facilities, especially of unique objects, the coefficient K1 should be determined by calculations with sufficient scientific justification, particularly with the use of non-linear dynamic methods.

Natural calamities cause destruction of highways and artificial structures that they accommodate, thus, inflicting a substantial damage onto the national economy. The authors describe various natural phenomena and geological processes typical for North Vietnam. The reasons for and the characteristics of each type of disasters are also provided in the article. The authors have generated a set of actions aimed at prevention or mitigation of damages, and they are enlisted in the article. The authors make their conclusions in respect of the future areas of research and the monitoring of interaction between the road surface, the transport infrastructure and the environment. Attainment of the aforementioned objective involves road surface monitoring to be accompanied by specific researches and compilation of maps of the areas exposed to frequent natural calamities. Timely notification of upcoming natural calamities and provision of effective recommendations are needed for the population to get prepared for the adverse events in advance. Besides, restriction of earth works in the areas exposed to natural disasters is necessary.Road building projects must incorporate environmental protection, organizational, technology and designelated actions aimed at the improvement of operating parameters of road beds of highways and at prevention of any further negative consequences in the course of operation of highways. Intensive wood planting and restriction of mining operations in specific areas are to be implemented.

In the article the problem of calculation of a construction basis system in case of earthquake is considered taking into account casual properties of basis soil in various points of the soil body. As a stochastic function in the calculation of linearly deformable basis, the deformation module, which accepts different values in the direction
x,
y,
z, was chosen. In the calculation of the system on non-linearly deformable basis as incidentally distributed sizes the following parameters were accepted: deformation module, shear modulus, specific adhesion, angle of internal friction. The authors of the article offer to consider initial seismic influence in the form of casual stationary process. In order to solve such problems modern software systems are proposed that solve differential equations of motion via direct integration with explicit schemes. The calculation in this case will be held on the synthesized accelerograms. A short review of the task solution of the beam lying on elastic basis, which was received by D.N. Sobolev at casual distribution of pastel coefficient in the direction
x, is provided in article. In order to define the objective, D.N. Sobolev gives expressions for a population mean and correlation function of stochastic function. As a result of the task solution population means and dispersions of function of movements and its derivatives were received. The problem formulation considered in the article is more complicated, but at the same time important from a practical standpoint.

The authors consider theoretical issues of the present-day interpretation and applicability of
the terms and concepts of the engineering geology and geoecology. The authors propose a new
approach to the formulation of definitions of the founding concepts of major categories of the engineering
geodynamics as the constituent part of the engineering geology. At the current stage of
development of the geoecology, the processes and phenomena typical for the geological environment
considered from the viewpoint of civil engineering are regarded as geoecological rather than
engineering and geological.
Examples of incorrect interpretation of these concepts of engineering geology replace the
study of the processes and phenomena of the engineering geology by the study of exogenous
processes in the upper zone of the earth crust. Negative processes underway in the geological environment
that are considered within the framework of the engineering geology should be assessed
as geoecological. The assessment of the present-day use of the term "geoecological processes and
phenomena" is based on the principle of indecomposability and unity of the geosphere. This fact
serves as the basis for the modern interpretation of concepts of engineering geology or geoecology
that relate to the geological environment and its use as the setting of construction works.
The authors demonstrate that the pollution of the atmospheric air or its transparency affect
structures. It causes changes in the hydrogeological conditions that may cause a flood or reduction
of the level of underground waters that influence the behaviour of bases of constructions.
Anthropogenic impacts that cause the temperature and chemical pollution of the subterranean hydrosphere
can lead to the dissolution of rocks, trigger karst processes, boost the speed of underground
waters, and, thus, trigger the mechanical suffosion in the sands. The concept of geoecological
processes and phenomena as the basic categories needs the assessment of the geological
environment when exposed to the anthropogenic impact.