№1 2019
№1 2019

№1 2019

№1 2019

Content

АКТУАЛЬНЫЕ ВОПРОСЫ И ОПЫТ ПРОЕКТИРОВАНИЯ ЗДАНИЙ И СООРУЖЕНИЙ В СЕЙСМИЧЕСКИХ РАЙОНАХ

Authors:    Editor   
Rubric:     Conferences. Symposia. Meetings   

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Engeneering seismology. Lecture 3

Authors:    Editor   
Rubric:     Past publications   

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Содержание: В этой лекции рассматривается поведение колеблющихся зданий и взаимодействие между их фундаментами и грунтом. Д-р Сюэхиро дает результаты действительных наблюдений над зданиями различных типов конструкции и особо отмечает характерные черты некоторых зданий, которыми объясняется причина их стойкости при большом землетрясении в 1923 г. Он также выясняет причину разрушения некоторых зданий.
Было установлено, что жесткое здание колеблется таким же образом, как и прилегающий грунт и нечувствительно к колебаниям грунта весьма коротких периодов, порядка 0,1 сек. В менее жестких зданиях колебания усложнены второстепенными вибрациями и такие здания менее подвержены разрушению. Следовательно, их собственное свободное колебание преобладало во время землетрясений с нерегулярными движениями. 
Деревянные фахверковые здания, тщательно построенные, и каркасно-стальные сооружения с каменным заполнением обнаружили высокие сейсмостойкие качества. Упругость грунта может более или менее ослабить разрушительное действие сильного землетрясения на каменные сооружения, имеющие относительно большой вес. В Токио здания с монолитной фундаментной плитой и без свай, расположенные на слабом, рыхлом, но уплотненном грунте, выдерживали толчки лучше, нежели здания с особыми свайными основаниями. Изучения подземных сейсмических движений приводят к выводу, что принцип углубления в грунт основания высокого здания с большим периодом собственного колебания не так выгоден, как это представляют себе некоторые инженеры. Для низких же зданий с коротким периодом собственных колебаний, наоборот, преимущества глубоких оснований бесспорны.


About Requirements of New Normative Documents to Reinforcing of Reinforced Concrete Designs for Construction in Seismic Areas

Authors:    Tihonov N.I.    Smirnova L.N.    Bubis A.A.   
Rubric:     Theoretical and experimental studies   

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To meet the safety requirements in the design of reinforced concrete structures in seismically hazardous areas, it is important to ensure the dissipation of seismic input energy in structures when their progressive collapse is included. For this purpose, plastic deformation of the calculated sections of reinforced concrete structures with the opening of cracks in reinforced concrete is allowed much higher than the maximum permissible. These conditions can be met, when a number of design requirements are met. These requirements are reflected in regulatory documents for the design and manufacture of building structures and materials, including reinforcing bar. The article present a comparative analysis of the requirements that have recently been published at normative technical documents, namely the SP 14.13330 and the standard of the organization «Earthquake engineering», and also requirements of the state standard «Reinforcing bar for reinforced concrete design» in relation to design for seismically dangerous areas are stated and explained. So, as one of the possible options, the authors consider the advantages of using screw fittings, for connecting rods with screw fittings it is recommended to replace welded joints with screw couplings.


Some Features of Modeling Design Accelerograms

Authors:    Smirnova L.N.    Uzdin A.M.    Prokopovich S.V.   
Rubric:     Theoretical and experimental studies   

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Summary:  At present, calculation of structures using earthquake accelerograms is becoming more and more important. However, the problem of modeling design accelerograms causes debates and contains various suggestions based on contradictory assumptions. Therefore, the value of complicated and time-consuming dynamic calculations can be rather dubious. The paper deals with some parameters of modeling design accelerograms. It is shown that the widely used method of input generation, developed by A.A. Dolgaya, gives rather rough approximations of synthetic accelerograms to real 
ones due to the insufficient number of model parameters.


Estimating Combination Coefficients of Seismic and Ice Loads

Authors:    Ottosha B. Sabirova   
Rubric:     Theoretical and experimental studies   

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Abstract: Combination coefficients of ice and seismic loads for earthquakes of different frequencies have been considered. As the density function of the ice load distribution, the Weibull law, supplemented by a delta function at the origin was used, which allowed us to take into account the absence of ice in the warm season. The interval between earthquakes was taken according to the Poisson law. It has been shown that the magnitude of the design loads significantly depends on the frequency of earthquakes, and the combination coefficients are practically independent. Combination coefficients determine equally probable pairs of actions, which in their term determine the dependence of the combination coefficient to ice loads on the combination coefficient to seismic ones.
An example of calculations for the region respectively with situational seismicity of 9, 10 and 10, using maps A, B and C of general seismic zoning maps of the territory of Russia is given


Linear Spectral Seismic Analysis of High-rise Building

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

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Summary: Linear Spectral Method (LSM) by origin is accurate only for single-degree- of-freedom systems. For more complicated systems (and real systems are always more complicated) LSM uses certain double summation rules to combine single-mode responses to one-component excitations. These rules are not precise, they are rather statistical; in different codes they are different. In fact, these rules are based on experience with structures of certain type. That is why the author thinks special check is necessary when one deals with structures having certain peculiarities (like high-rise buildings). This is essentially a check for the applicability of the summation rules. Algorithm for such a check – to compare the results obtained in the time domain for excitation timehistories with LSM results provided input spectra for LSM are obtained from the same time-histories and damping in oscillators is equal to the structural damping. In the present paper seismic responses are compared in the format of the integral response forces under the base mat. The main result is that conventional summation rules in LSM lead to the considerable deviation in the results including underestimation of the response forces.


Grounds as a Factor of Seismic Safety for the Territories of the South of East Siberia

Authors:    Akulov N.I.    Berzhinsky Yu.A.    Akulova V.V.   
Rubric:     Seismic zoning   

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The article presents the results of studies conducted in the fall of 2008 in the southern part of Lake Baikal, where the Kultuk earthquake occurred. The impact of the earthquake on rocks and foundations of social and public buildings (hospitals, schools, etc.) in Slyudyanka, pos. Kultuk and in other settlements. A large amount of factual material on soil reinforcement by cementation was obtained during the demolition of residential buildings in the city of Irkutsk. It was established that the destruction of the foundations of buildings and structures, which occurred as a result of the Kultuk earthquake in the Slyudyansky region, is due to: a) in some cases, the almost total absence of a foundation cushion; b) a combination of rocky and dispersed soils at the base of the foundation that caused the heterogeneity of the bearing layer, which led to the destruction of the building; c) heterogeneity of the composition, state and properties of dispersed soils at the base of the foundations, when uneven deformation (compression) of the soil contributed to the emergence of a different amplitude system of oscillations of the foundation and walls of buildings during an earthquake.