№5 2019
№5 2019

№5 2019

№5 2019

Content

Calculation of Damaged Reinforced Concrete Plates of Covering Taking into Account the Corrosion of Concrete and Fittings

Authors:    Minasyan A.    Piatikrestovskii K.   
Rubric:     Theoretical and experimental studies   

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The article presents a diagram method of calculation of reinforced concrete slabs. The considered flor slabs were subjected to intensive inflence of climatic conditions of Moscow, as a result of which they received diffrent schemes of damage. The bearing capacity of these plates varied depending on the scheme (section) of the plate damage. At the same time, concrete tests of damaged sections of structures, as well as corrosion-damaged reinforcing bars were performed. The diagrams of concrete deformation of undamaged and damaged areas and the diagrams of stretching of damaged reinforcing bars are obtained. On the basis of experimental diagrams of concrete and rebar deformation, a method of analytical determination of the bearing capacity of the plates was developed.


Options of Execution of Drives in the Device of Seismo Platform

Authors:    Lobanov A.   
Rubric:     Theoretical and experimental studies   

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To provide reciprocating motion or other type of movement in modern seismic platforms, various types of linear actuators are widely used.
At the moment, an urgent task is to create a seismic platform that allows you to reproduce seismic loads in a wide range of vibration frequencies from 0.2 to 100 Hz, which allows you to simulate all the dangerous frequencies of real impacts.
The disadvantage of modern seismic platforms is a limited range of oscillation frequencies due to the complexity of drives, which are to provide long-period and high-frequency oscillations typical of real accelerograms. The correct choice of a drive for implementing reciprocating motion is an important task in designing and manufacturing seismic platforms, both from technical and economic parts of view. These questions are considered in the paper.
The comparative analysis of linear drives is given. Hydraulic, pneumatic, Electromechanical systems of linear displacement, as well as linear electric machines as a separate class of electric machines are considered. The peculiarities of realization of the linear actuators in the design of modern seismic platforms, for example seismic platforms protected by the patent [7]. To implement the method of separation of impacts in modeling seismic vibrations, the authors propose a two-level seismic platform design. Using this approach, the velocity pulse is transmitted through the upper drive, The lower drive will provide high-frequency oscillations. To ensure a wide range of oscillation one of the variants of a system of linear actuators to implement the specifid effcts is a combination of high frequency hydraulic actuator and linear electric machines for the implementation of low-frequency vibrations or residual offets.
The use of this combination of drives will reduce material costs when implementing such a system on a fully hydraulic drive, without losing the accuracy of the tests.


Absolute Сumulative Velocity as a Measurement of Earthquake Strength

Authors:    Prokopovich S.V.   
Rubric:     Theoretical and experimental studies   

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In this paper the aspects of determination of energy characteristics of seismic input are studied. The range of various energy characteristics is estimated. The index of range of statistical data shows that using cumulative absolute velocity is preferable to using Arias intensity. The parameters of distribution of absolute cumulative velocity values are described. Each mark on the Richter scale corresponds to one constant velocity value.


The Defiition of the Effctive Length of the Accelerogram at the MacKenzie Earthquake Example in 2018

Authors:    Kharlanova S.    Harlanov V. L.   
Rubric:     Theoretical and experimental studies   

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 For deterministic analysis of building structures it is necessary to set real or synthesized accelerograms as input data. This analysis requires considerable time, as it is performed by a step-bystep method. Real accelerograms can be of considerable length and
require a lot of calculations. As a rule, accelerograms have maximum values of amplitudes on a small temporal site. The article considers the possibility of using only a part of the accelerogram without loss of adequacy of calculation of seismic reactions of inelastic systems. The method of truncation of extended earthquake accelerograms for the analysis of nonlinear systems is defined. The necessity of application of the energy criterion is shown. Nonlinear oscillators for different materials are considered.


Development of Algorithms for Interpreting the Method of Standing Waves for the Study of Buildings and Structures of Complex Constructions

Authors:    Emanov Alexandr F.    Bakh A.A.   
Rubric:     Theoretical and experimental studies   

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According to the results of research on complex engineering objects, results were obtained that demonstrate significant deviations from the models of buildings and structures that are used as the basis for calculating seismic resistance and structural stability. Firstly, 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 multiplicity 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 the fields of standing waves, It 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.


Statistical Modeling of the Earthquake Input

Authors:    Uzdin A.M.    Smirnova L.N.    Sorokina G.V.    Abakarov A.    Zaynulabidova H.    Prokopovich S.V.   
Rubric:     Theoretical and experimental studies   

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The main problem of modeling statistical seismic vibrations is correct input accelerogram setting. The analysis of the known seismic input models showed the erroneousness of using them in analyzing seismically isolated systems. These statistical models allow one to obtain either reliable accelerations or reliable displacements. However, complicated input models do not quite correspond to real earthquakes. Energy characteristics were not considered at all in the problems of accelerogram statistical modeling. A new model of seismic input, including a random pulse, has been considered. Three parameters has been added to the input model: the magnitude Мw , the epicentral distance R, and the moment when the pulse appears. Varying these parameters within the set limits allows one to adjust additional input characteristics. An example of the proposed process is given.


Some Comments on the New Generation of Standards in Earthquake Engineering. Part I: General Requirements and Seismic Input. Part II: Seismic Forces in Linear-spectral Method.

Authors:    Tyapin A.G.   
Rubric:     Theoretical and experimental studies   

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The author gives his comments on the already started process of the revision of Russian Standards in earthquake engineering. He submits certain recommendations on the process and some recommendations of the general format of the new generation of Standards. Then the author in details discusses the seismic input in the Standards. The goal of the present text is not to give answers, but rather to stress main questions and to list the points where the authors of the future Standard will have to make a certain choice between alternatives. The author describes the alternative solutions for these choices. Some of such issues follow. The multi-level seismic input; the format of the seismic input required from seismologists, the non-exceedance level for seismic input; the location of the control point where seismic input is given. Besides, the issues of the intensity degrees and peak accelerations, the shape of the normalized response spectra, the composition of the wave fild (i.e. non-vertical seismic waves) are also discussed. Finally, the authors comments on the «dangerous directions of the seismic excitation» concept.
The author submits certain recommendations on the description of the linear-spectral analysis. Principal text is accompanied by the Comments. The author suggests the following changes. Matrix equations are introduced, as matrix calculations correspond to the current level of analysis. Mass matrix is populated (and not diagonal, as previously used). Residual mode is introduced as an alternative to the achievement of 95% total mass by the accumulation of modal masses. Seismic excitation is three-component without non-physical “dangerous directions” concept. Normalized spectra, responsibility coeffient, modifid damping coeffient are explained explicitly. Coeffient of non-linear response is applied to certain parts, and not to the whole structure. In the combination of modal responses the inter-correlation of the low-frequency modal responses is explicitly accounted for. If the suggested terms are fulfiled, the linear-spectral analysis should give the results like the time-domain analysis (provided response spectra are calculated from the actual components used in the time domain analysis). At the same time there is a certain smooth transition from the previous codes.


The Use of Annealed Aluminum Salt Slag to Obtain a High Strength Antiseismic Brick

Authors:    Abdrakhimov V   
Rubric:     Theoretical and experimental studies   

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Taking into account the reduction of reserves of traditional natural raw materials, it is necessary to find new ways to replace it with different types of waste. The experience of advanced foreign countries has shown the technical feasibility of this area and the use of more as a tool to protect the environment from pollution. In the present work, instead of dehydrated clay, it is proposed to use burnt salt aluminum slag as a otoschitel. Highstrength earthquake-resistant brick M200 was obtained on the basis of inter-shale clay and burnt salt aluminum slag without the use of natural traditional raw materials. Proposed zaparovanny way of dressing aluminum oxide aluminum salt slag. Salt aluminum slags are fired at a temperature of 900-920 ° C to the content of losses during calcination not more than 4%. After firing of salt aluminum slags in the temperature range 900-920 ° C, their chemical composition was significantly enriched with aluminum oxide. The resulting ceramic brick corresponded to the brand 200, from which, thanks to the use of burnt salt aluminum slags, it is possible to erect bearing walls of the lower floors of buildings of higher floors (15 floors or more). Innovative proposals have been developed for the use of waste products: inter-shale clay and burnt salt aluminum slag in the production of high-strength ceramic earthquake-resistant bricks.
High-strength earthquake-resistant brick M175-200 was obtained on the basis of inter-shale clay and burnt salt aluminum slag without the use of natural traditional raw materials. The burnt salt aluminum slag containing more than 70% A1 2O3 increases durability and frost resistance of products of a ceramic brick. The absolute advantage of the use of multi-tonnage waste of salt aluminum slag and inter-shale clay – waste oil shale is unloading the environmental situation.