Increasing the seismic resistance of operated buildings using special seismic protection methods

The change in the level of seismicity of buildings and structures occurs as a result of updating the maps of general seismic zoning. Ensuring the seismic resistance of buildings and structures is a factor that must be taken into account, especially during construction in seismically active regions. Nowadays, one of the main approaches to increasing seismic resistance is the use of various seismic isolation systems. It is not always profitable and rational to increase the seismic resistance of building structures or foundations for equipment by simply increasing the strength. A classification of seismic reinforcement systems is given, among which the most sparing are special methods of seismic protection in the form of seismic isolation. Practical examples of the use of seismic isolation systems to improve the seismic resistance of existing buildings are given. A computational study was carried out, the result of which showed the effectiveness of using rubber-metal supports for hanging the seismic resistance of buildings.

Probabilistic estimation of reliability values for frame buildings based on the results of certification taking into account tectonic faults

With budget funding for two years in 2017-2018, the total certification of the housing stock of multi-apartment buildings was carried out for the first time. A total of 8,171 buildings were entered into the database, of which 1,847 are multi-storey frame buildings of various storeys and design solutions. It is established that 1628 frame buildings are earthquake-resistant, 59-buildings with the first flexible floor are non-earthquake-resistant and 160-are located in the zone of tectonic faults on the territory of the city. The hypothesis is accepted that buildings located in the zone of tectonic faults will be destroyed. Under these conditions, quantitative estimates of the failure probability and reliability values for frame buildings of various types were obtained for the first time. The frequency of earthquakes is taken into account according to the current "Map of seismic zoning of the Republic of Kazakhstan". The results of the reliability and failure estimates are used for practical recommendations to reduce the risk and expected losses in possible earthquakes. Total reinforcement of frame buildings with the first flexible floors (59 buildings) is proposed. However, the conditional probability of failure for a group of residential frame buildings will remain nonzero. The method of amplification should be determined based on the results of experimental studies.

The antiresonance phenomena in seismic microzonation

The interference of incident and reflected seismic waves in the ground massif near the day surface is the cause of resonant effects. In the practice of seismic microzonation (SMZ), a resonant increase in the total seismic intensity is of particular importance. At the same time, the presence of inverse layers in the ground layers interference leads to a decrease in the intensity of the total seismic impact, what is naturally named antiresonance. The article considers the conditions for the occurrence of antiresonance and evaluates the limits of its effectiveness. The natural and man-made causes of antiresonance and the possibility of using it to reduce the intensity of seismic impacts are particularly noted.

Assessment of the resistance of monolithic reinforced concrete bearing systems to progressive collapse based on the principle of the level of permissible damage

The paper presents a method of using the reduction factor to ensure the stability of monolithic reinforced concrete bearing structures to progressive collapse. Studies have established the values of the reduction factor based on the accepted value of the relative deformation corresponding to the formation of an admissible zone of "destruction" of the support section of the overlap under the action of transverse forces, as the main criterion for asessing the stress-strain state of monolithic reinforced concrete structures for the failure mode of a vertical supporting structure. The accepted deformation criteria for a special limiting state correctly reflect the conditions for the formation of an admissible amount of damage to elements of bearing reinforced concrete systems. The reduction factor (K1) obtained in the framework of the research performed is the most important deformation characteristic of the special limiting state of monolithic reinforced concrete bearing systems of buildings and structures for an emergency design situation associated with the failure of a local structural element.

Use of recycled tires for earthquake protection of structures

The article presents numerous structures of earthquake-resistant foundations that have been developed by the authors and other engineers over the past more than 30 years, in which recycled metal-cord tires are used. The designs of dynamic dampers of dynamic vibrations, in which the containers for bulk fillers are made of recycled tires, are presented. Recycled tires are also effectively used in the creation of earthquake shields, as well as reinforcing elements and seismic insulation layers of earthquake-resistant ground dams. In all the above-mentioned technical solutions, the earthquake resistance of buildings and structures is achieved due to the unique geometric and physico-chemical-mechanical properties of recycled rubber tires with a metal cord.

Application of the wavelet transform in filtering the noise of real earthquake accelerograms

In the deterministic analysis of building structures, real accelerograms are used as input data. Very often, only instrumental recordings of accelerograms that are not cleared of noise are publicly available. Such accelerograms cannot be used directly in the analysis of building structures. Various broadband filters are used to adjust the instrumental recordings of accelerographs. This article discusses the possibility of applying filters based on the wavelet transform. The technique of the algorithm of filtering from the noise of the source data is considered. As an efficiency of this filtering algorithm, a comparative analysis of the dynamic coefficient and the energy criteria of the pulse and Arias for the corrected and instrumental accelerograms is carried out.

Consideration of the vertical load from a tsunami on bridge structures

A significant part of the territory of the Russian Federation is exposed to various natural disasters. One of the most destructive are tsunami waves. At the same time, for the development of these territories, there is a need for the development of transport infrastructure, which implies, among other things, the design of bridges. To ensure the reliability of bridges in the event of tsunami, it is necessary to fully take into account the possible impacts from these waves. In Russia, there is a document to determine the load from the tsunami. But, despite the existence of this document, the issue of taking into account the loads from the tsunami on various structures remains relevant. In particular, there are no clear guidelines for accounting for vertical loads from tsunami waves on bridge structures. With the help of the studies carried out on computer modelling of the wave roll-up on the bridge structure, this article proves the need to take into account the vertical loads from the tsunami, and also proposes a method for determining its numerical values. This study can complement the basic methodology for determining the loads from tsunami waves on bridge structures and help designers fully account for this dangerous natural disaster.

Solving a direct problem as a new method of seismic microzonation

The article describes a new type of seismic microzonation, called the method of solving a direct problem. The main methodological technique in this case is the formation of models of the soil layer on the basis of complex engineering-geological and geophysical studies. An original computer simulation technique based on the use of a short acceleration pulse as the initial seismic impact is proposed. In the calculations of the increment of seismic intensity, a new formula is used that takes into account all the factors of the influence of soil properties on the parameters of seismic impacts – seismic rigidity, water saturation, resonant effects and the nonlinearity of the reaction of soils to strong seismic impacts. Based on the obtained data, the models of ground layers at the construction site are mapped and the parameters of seismic impacts that correspond to the properties of each model of ground massif are determined. The proposals presented in the article are reflected in the regulatory documents devoted to the SMZ of objects of increased responsibility and territorial planning.

Multi-level designing structures in tsunami-prone areas

The paper proposes a two-level approach to the calculation of structures for the tsunami effect. The concept of the design tsunami and the maximum design tsunami and their corresponding limit states is introduced. The estimated loads on the bridge piers from the design and maximum design tsunami are estimated, depending on the territory danger and the bridge responsibility. At the same time, bridges, in accordance with the approach adopted in transport construction, are divided according to their degree of responsibility into four categories. A formula is obtained to estimate the design splash value for the design and maximum design tsunami, depending on the bridge category. In addition, graphs are provided showing the frequency of the tsunami and the calculated wave height corresponding to this frequency. To estimate the combination coefficient of wind and tsunami loads, their equally probable pairs are considered. At the same time, the Weibull distribution is used to set the wind load, and for the tsunami load, the distribution given in the Code of Rules for Ensuring Tsunami Safety is used. Taking into account such load pairs is relevant for bridges with high piers, when the height of the splash does not exceed the pier height and there is a high probability of a simultaneous combination of wind and tsunami loads. The paper presents the calculations of surges for two types of tsunamis: the design one with a repeatability of once in 50 years and the maximum design one with a repeatability of once in 500 years for the Kamchatka region and the Kuril Islands for bridges of the first and second categories. Studies show that for the design tsunami and the maximum design tsunami, the coefficients of combinations with wind load differ significantly.

Signs of the "one-mode" response forces in linear spectral method: comparison of conventional and standard approaches

Two variants of linear-spectral method (LSM) are compared in the paper: the conventional one, prescribed in several foreign standards, and "Standard" one prescribed in the Russian Standard SP 14.13330. "One-component one-mode" responses, obtained by static analysis in the conventional LSM are combined twice: first for different modes but for each single excitation component, then for different excitation components. In the "standard" alternative LSM variant first one chooses the "most dangerous" direction of the one-component excitation for each mode, then one obtains the "one-mode" response for this excitation, and finally these responses are combined. In both cases the combination is performed using the complete quadratic combination (CQC) rule, accounting for the correlation between one-mode responses. "Standard" variant leaves some uncertainty: the "dangerous" direction can be changed for the opposite one. Such a change leads to the sign change in the one-mode response. This is of no importance for the non-correlated responses, which are combined using the SRSS rule. However, for the correlated responses as it is shown in the paper using sample problem the uncertainty in the signs can lead to the incorrect results, and the error can be significant.