Introduction. To ensure the functioning of earthquake-affected areas, it is very important to ensure the earthquake resistance of bridges and other transport infrastructure facilities. One of the characteristic damages of bridges during an earthquake is the dumping of superstructures from their supports. The discharge of superstructures is caused by different ground conditions under the supports along the length of the structure, which in turn leads to different perturbations of the supports during an earthquake.

Materials and methods. The assessment of the course of the supports of a girder split bridge in Uzbekistan is considered. The ground conditions under the supports of the bridge vary along the length of the structure. It is necessary to calculate the motion of the bearing of bridge in order to exclude the dumping of the superstructure. The authors propose to evaluate the course of the supporting part of the bridge in the development of the linear spectral theory of structures calculating for earthquake resistance, using the mathematical apparatus of the theory of random functions. Usually, the correlation coefficients e are determined under the assumption of stationary processes. In this case, each process is defined by its own spectral density. Various cases of correlation were considered: the correlation between fluctuations of the points of the daytime surface under the supports, the correlation between fluctuations of the top of neighboring supports and the correlation of fluctuations of the base and top of the supports. For all cases, the corresponding correlation coefficients were calculated, which were further taken into account when calculating the motion of the supports.

Results. For the considered three-span bridge crossing with different structural solutions of supports and different soil conditions at their base, the following displacements of the base, relative displacements of the top of the supports, and total displacements were calculated. An assessment of the mutual offsets from above has been performed. Displacements of the top of the channel supports, taking into account the heterogeneity of the acceleration field under the supports. The mutual displacements of the base points in the absence of correlation of vibrations, the mutual displacements of the top of the support in the absence of correlation of vibrations are determined, and the mutual displacements of the base points and the mutual displacements of the top of the support are calculated taking into account the correlation for the case of white noise.

Discussion. An analysis of the results showed that the displacements of the top of the supports are quite significant. Even estimating the displacements as the root of the sum of the squares gives the motion of the supporting part more than 50 cm. Based on the results obtained, recommendations were made for designers, firstly, on the need to develop the support head, and, secondly, on additional reinforcement of the support to compensate for the moment from the vertical reaction of the superstructure with a large motion of the support part, and, thirdly, on the expediency of installing stoppers to eliminate excessive displacements.

Conclusions. The calculation of the motion of the supporting part is a necessary element in assessing the seismic resistance of bridges. The motion of the support part depends on the relative displacements of the top of the supports and the heterogeneity of the acceleration field along the length of the bridge. When designing bridges with different supports and with different ground conditions under the supports, it is advisable to combine the spans into a chain, for example, by using rubber support parts.

Introduction. The series of recent earthquakes that have taken place on the territory of Russia has once again clearly shown that this natural disaster is characterized not only by its unpredictability, nature, and direction, but even by a significant duration, as was the case, for example, in Kamchatka in 2025. It is possible to resist the elements only with the use of reliable and proven earthquake-resistant construction constructive solutions, to these include multicommunicated systems made of precast reinforced concrete structures, among which bulk-block structures form a special group. The effectiveness of their operation significantly depends on the presence of additional damping elements in the system. The article presents an analysis of some of these solutions, which is necessary to understand how structures work during earthquakes.

Aim. To show the features of structural solutions of three-dimensional block buildings in the presence of damping elements in them in the form of friction bonds that ensure continuous energy dissipation during the entire exposure period.

Materials and methods. The analysis of existing structural solutions of three-dimensional block buildings with the inclusion of damping elements in the form of friction bonds is carried out.

Conclusions. Additional computational and experimental studies are needed to substantiate the possibilities of the considered solutions for three-dimensional block buildings with friction elements.

Currently, seismic isolation technologies are becoming increasingly widespread in earthquake engineering. The technology, known since ancient times, has been developed in the modern world. The effectiveness of various seismic protection technologies used has been repeatedly confirmed after strong earthquakes in many countries of the world, including Russia. That is why scientific engineering does not stop working to improve the seismic protection of buildings and structures. The article presents the main conceptual seismic protection systems, examines existing design solutions for the implementation of seismic isolating devices, taking into account the peculiarities of their operation during earthquakes, since the reliability of the operation of seismic protection systems largely depends on the characteristics of the seismic impact, its frequency component, direction, intensity, etc. The systems developed and used in Russia currently have economic and social efficiency, making it possible to achieve, in comparison with traditional structures, an increase in the seismic reliability of structures, a reduction in the cost of anti-seismic measures, a reduction in damage from earthquakes, and more accurate assessments of investment and insurance risks.

The active development of the Arctic zone, Siberia and the Far East in Russia in the last decade has prompted the authors to return to the problem of construction of structures in areas that may be affected by a number of natural phenomena during construction and operation. In the article, the authors narrow down the identified problems and analyze only options for the construction of earthquake-resistant buildings on permafrost soils, the situation most common in the territories of the so-called permafrost. The review and analysis of the existing and most frequently used construction options on permafrost soils according to the I and II principles are presented and the possibility of using special seismic protection systems at such facilities is assessed. The requirements for the characteristics of backfills in the case of construction according to principle I, variants of structural solutions of pile foundations during construction using principle II are given. The analysis of constructive solutions applied more than 40 years ago in the construction of residential blocks of buildings of the 122 series in Severobaikalsk, well-proven during the past earthquakes. The authors give examples of various variants of seismic protection devices when implementing the principle of seismic isolation, the implementation of which is carried out in the usual way by introducing various malleable support elements into the foundation part of the building. In the conclusions based on the results of the study, recommendations are given for the construction of earthquake-resistant buildings for the conditions of the Arctic zone.

During individual construction in seismic areas, the designer often has to solve problems that violate certain requirements of regulatory documentation on the configuration and number of storeys of the building, architectural and planning solutions of its internal and underground space. In this case, it is necessary to develop special technical conditions (STC) with compensating measures for these deviations, ensuring high seismic resistance of construction objects. The article considers the possibility of using the technology of plastic deformation of the bearing structural elements of the building to ensure the seismic resistance of the object, and also offers a method for assessing the degree of plastic work of the structure.

Introduction. The problem is considered and the relevance of studying the behavior of buildings and structures with seismic isolation systems using lead rubber bearing under real seismic impact, as well as assessing their technical condition after the earthquake, is emphasized. The experience of studying the behavior of base isolated buildings under real seismic impact abroad and in Russia is given.

Materials and methods. The dynamic parameters seismic isolation of a reinforced concrete building using lead rubber bearing are investigated. Registration of seismic vibrations of the building was performed by a stationary station for dynamic monitoring. The results of processing the records were obtained based on the interpretation of monitoring data, including harmonic analysis, determination of the power spectral density and signal transfer functions, as well as the application of wavelet transform methods.

Results. The data of dynamic monitoring of the seismically isolated building of the sea station located in the city of Petropavlovsk-Kamchatsky for the reporting year 2021 of monitoring are presented. The analysis of the reaction and dynamic parameters of the building during the most intense seismic events for the reporting period was performed.

Conclusions. The analysis of the results showed that the system of seismic isolation of the building during earthquakes of low intensity operates in the area of the initial rigidity of the seismic isolation supports, and the dynamic parameters of the seismically isolated building depend on the intensity of the seismic impact. It is concluded that the time-frequency analysis using wavelet transform methods has advantages in the analysis of dynamic monitoring data of buildings and structures with seismic isolation systems over the Fourier transform. The methods for analyzing dynamic monitoring data described in this article can be effectively used to assess dynamic parameters and then analyze their changes during the operation of base isolated buildings and structures. The study presented in this article shows that with the help of dynamic monitoring of buildings and structures, one can get a more complete and detailed understanding of their dynamic behavior, identify damage in the structural system of a building, and detect their undesirable or specific reactions that could not be taken into account when designing.

Engineering methods for finding the average (averaged) velocity of propagation of longitudinal waves in pipelines with flexible joints are presented. By accurate analysis of the problem of oscillations of a one dimensional periodically inhomogeneous structure it is shown that the results of engineering approaches for rod velocity are the first or long-wave asymptotic approximation which valid when the period of external influence (the length of the seismic wave) significantly exceeds the size of the periodicity cell of the pipeline (the length of the pipe with a joint). Thus, it is established that when this condition is met, the problem of pipeline dynamics with joints is reduced to a much simpler problem of vibrations of a homogeneous pipeline, the velocity of wave propagation in which is equal to the found average value.
Numerical examples are given that demonstrate a significant (sometimes by an order of magnitude) decreasing of the rod velocity in the presence of flexible joints.

The application of the response spectra method for extended damped systems with a point support on the base is considered. The support excitations can be different. External and internal damping is taken into account, it being assumed proportional i.e. admitting an exact or approximate decomposition of motion according to the undamped system modes. It is noted that the presence of external damping leads to additional system perturbation, i.e. to additional members appearance in the right part of motion equations. It is shown that well-known formulas of the response spectra method for systems on a rigid platform are kept intact, but the vector of load projections on the directions of generalized coordinates is modified taking into account the influence of support displacements on generalized loads in the system.

The authors present their view of the problem, with the frame of the discussion devoted to equations of seismic oscillations taking into account damping. The oscillation equations taking into account external and internal damping are written down. The cases of homogeneous and inhomogeneous acceleration field of the day surface along the length of the structure are considered.

As a result of the release of GOST 34028-2016 «Reinforcing bars for reinforced concrete structures» the manufacturability of new kinds of reinforcing bars, taking into account the needs of different areas of construction were increased. The materials of the present study prove the ability of reinforcement with a multi-row (six-row and screw four-row) arrangement of transverse ribs on its surface to maintain adhesion with concrete even at the stage of exceeding the limit values of deformation. This factor, as well as high endurance at cyclic dynamic effects, possibility of connection using couplings of four-row screw reinforcing bars and anchoring it with nuts, expands the possibilities of using the new valves not only in earthquake engineering, but also in nuclear power, transport and other types of construction. The new reinforcing bars of domestic production are able to gain a leading position not only in the domestic but also in foreign construction markets.

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.

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.

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.

Estimation of earthquake stability of reinforced arch viaduct of tunnel type strengthened by corrugated metal arch structure has been carried out. The structure calculation has been done using the finite element diagram including railway the embankment, the composite arch and soil base. Along the contour of the design area was placed the damping boundary. Obtained system mode parameters (frequencies and damping) were used for generating design accelerograms. It is shown that in the process of strong earthquakes (MDE) in the arch impost and crown may occur plastic hinges. When this becomes the arch turn from hingeless one into two or three — hinge arch, but does not lose bearing capacity. The recommendations for the reinforcement of structures under consideration are proposed.

It is shown that in many cases while calculating bridge spans it is necessary to take into account the soil-structure interaction. If the pier is higher than 5 m, energy dissipation for the main oscillation mode is determined substantially by energy losses, caused by wave propagation in the soil base, thereby the dynamic ratio drops significantly. Furthermore, if a bridge span is shorter than 55 m and the base modulus of deformation Eo < 30 MPa, the force in the piers can be determined by the second mode, for which the superstructure and piers oscillate in antiphase. For bridges with spans over 80 m long at Eo > 30 MPa, seismic forces for spans and piers are determined by the first oscillation mode. 

The possibility of using a response spectra method (RSM) for the calculation of structures with mass dampers (MD) is considered. It is shown that the Guide Lines SP 14.13330.2014 allows us to take into account the MD behavior and estimate its efficiency. However, it is impossible to optimize damping in the mass damper elements. To take into account the damping RSM, including amendments to the damping and the mode correlation, may be modified. In this case, satisfactory results are obtained when the relative weight of MD less than 0.7 and the construction damping of less than 0.3 (15% of the critical value). For the great mass of the MD optimum damping is more than 20% of the critical, and there is a need to consider the effect of modal damping.

The reduction factor K1 included in the formulas of Guidelines for calculating seismic loads for bridge piers has been evaluated. The dependence of the reduction factor on the ratio of pier reinforcement has been obtained. To this aim the non-linear finite element calculation of the pier under monotonous loading has been carried out and the elastic limit and damaging displacement has been obtained.