Use of earthquake-proof foundations in the design of residential buildings for the areas of the northern climate zone

. The regions of the Far North and the territories equated to them today have a great potential for development, which is primarily due to the presence of rich natural resources, among which are unique resources of hydrocarbon raw materials, the development of which directly affects the prospects and directions of development of fuel and energy complex and related industries, which in turn requires the development of several support facilities for various purposes, without which the existence of any enterprise is impossible The article deals with the constructive solution for the construction of urban buildings adapted for specific natural and climatic conditions, as well as the conditions of joint manifestation of permafrost and seismic impacts of high intensity. The technical result is achieved by reducing the effect of seismic loads, by developing elements of special stationary seismic protection (seismic insulation), representing a system with a seismic insulating sliding belt, which is mounted between the heads of piles and the building rostrum. The proposed solution makes it possible to increase the seismic resistance of buildings erected on a soil base according to the first principle by reducing the impact of the stresses arising in the structural elements.


Introduction
The northern climatic zone occupies significant areas of the Russian Federation, which include the entire territory of Yakutia, the northern parts of the Krasnoyarsk and Khabarovsk regions, the Irkutsk and Magadan regions, and part of the Kamchatka, Tyumen, and Arkhangelsk regions [1]. In addition, part of this zone, affecting regions of the Far East, Western and Eastern Siberia, is under the joint influence of a harsh climate characterized by cold winters, short summers, strong winds, and complex engineering and geological conditions, together with seismic activity, which varies from 6 to 10 points. These areas have significant deposits of natural resources-gas, rare metals, oil, and coal, the extraction and development of which is impossible without the development of proper transport infrastructure, as well as ancillary facilities included in it (railway stations, airports, administrative buildings, etc.). It is also worth noting that the development of the transport network in the northern climate zone raises the question of the need to build settlements with the necessary infrastructure, which includes transportation facilities, cultural and community facilities, as well as residential buildings. The existence and functioning of any enterprise in the transport and extractive industries are impossible without human beings, who must be provided with a place to live, conduct their lives and spend their leisure time. Thus, one of the main objectives in the design of civil buildings in the Far North is to ensure comfortable and safe conditions for a sufficiently long stay of people in them. This article presents the results of the study of the proposed solution of a large-panel residential building of medium height, adapted for natural and climatic conditions close to the extreme, with the presence in the region of high seismic activity and permafrost.

Northern climate zone, features, and, issues
Being a sufficiently promising region with a high development potential [2], as well as with a rich reserve of minerals (about 60% of oil, about 60-90% of gas, and, a large number of rare metals and precious stones), the northern climatic zone has several features, among which we should note the poorly developed or absent transport and logistics infrastructure, high outflow of the local population. In addition, there is an acute issue with the state of the climate. The annual ease in the level of humidity and reduction of glaciers caused by global warming, as well as melting of permafrost leads to deterioration of the technical condition of existing infrastructure (bridges, roads, buildings, and structures of mining industry, residential buildings, etc.), which over time are damaged and lose their bearing capacity due to melting of soils, which can have a significant impact on the provision of human life, which was noted in the scientific study of W. Timlin, A. Meyer, et al. [3].
Under conditions of global warming, thawing of permafrost causes its degradation, which leads to a reduction of its area, increase in temperature, subsidence of the land surface, and thawing [4]. As noted in the scientific paper by Serditova N. Е. [5], to prevent the complication of this condition, it is necessary to improve methods of monitoring, strengthening of control, and supervision of water bodies. As a result, to prevent the deterioration of the technical condition of the infrastructure of server areas, an improved approach to forecasting and identifying their damage, assessment of climate-induced damage, for subsequent adaptation of design, construction, and operation to new climatic conditions is required [6].

Joint manifestation of permafrost and seismic activity
As noted earlier, some territories of the northern climatic zone of the Russian Federation are characterized by a combination of several special natural and climatic conditions-high seismic activity, and permafrost, such regions include the Far East (Amur region, Transbaikal region, Kamchatka region, Magadan region, Republic of Buryatia, Republic of Sakha (Yakutia)), Eastern Siberia (Krasnoyarsk and Transbaikal regions, Irkutsk region, Republic of Buryatia), Western Siberia. In this regard, the design and construction in these territories should be guided by several basic principles, by the requirements of the code of regulations SP 25.13330 "Foundations and Foundations on Permafrost Soils": -Principle I am based on keeping the foundation soil in permafrost condition for the period of construction and operation of buildings and structures [7]; -Principle II implies the use of foundation soils in the thawed or thawed state during operation [7].
Based on this, in most cases, preference should be given to the I principle of construction, which is conditioned by SP 25.1330 and the recommendations on the design of foundations and foundations on permafrost soils. In the construction according to this principle, the main type of foundation is a pile foundation with a high upstand, which can act as seismic isolation by making a pliable connection between the soil foundation and the above-ground part of the building, which helps reduce the effect of seismic loads on the building [8]. However, the use of this type of foundation is possible only if the score of the construction site does not exceed 7 points, because, under the action of seismic loads on the building, the junction of piles and derrick is the most dangerous, where there may be the greatest movement, leading to the rocking of the building. In the case where the ball rating of the construction site is higher than 7, it is necessary to introduce seismic insulation elements into the foundation design, thereby increasing the seismic resistance of the object. On the other hand, the seismic resistance of buildings can be improved by the traditional method by increasing the crosssection and stiffness of the bearing elements of the building structures. The use of this method leads to a significant increase in the material intensity and weight of the structure, and as a consequence, to an increase in the seismic load and, ultimately, to a significant increase in the cost of construction. In this regard, the most preferable is the unconventional method involving the use of seismic insulation systems [9], some of which are presented below: • Seismic shock absorber.

•
Kinematic foundations, which are movable elements with a spherical heel that rests on a solid surface (slab). When the inertial load on the building occurs, the supports make movements along a curvilinear trajectory, as a result of which the building is lifted when the support rotates and the deformations and loads are reduced.
• Seismic isolated sliding belt, arranged between the foundation of the building and the above-ground part, and, when an earthquake occurs, the energy is dissipated by sliding friction [10]. This system of seismic isolation allows to reduce the calculated seismicity of the building by 1 point, to reduce the estimated cost by 3-6% due to saving steel by 5-7%, according to the recommendations on the design of buildings with a seismically insulating sliding belt and dynamic vibration dampers.
• Inertial damper, which is a massive block of reinforced concrete or steel, which is installed on the ton technical floor of the building and creates vibrations with a frequency similar to the inertial frequency of the building.
• Systems with switching-off couplings, the work of which consists in the fact that under the influence of inertial loads the system can change the dynamic characteristics in time, by the destruction of the bonds when the peak amplitudes of oscillations. As a result of the destruction of the switch-off coupling, the frequency of free oscillations decreases, and the period increases, due to which the load from the earthquake is reduced [10].
• Systems with coupling switches differ from those discussed above in that they do not disconnect couplings, and there is no need to restore them after a seismic event. This system can be used in areas with different earthquake intensities because it operates under seismic effects with high accelerations and low frequencies.
As practice shows, the construction of buildings and structures according to principle II with a combination of seismicity and permafrost soils is possible only in those areas where the average annual temperature fluctuations are significant, which in turn affects the temperature regime of soils and the permafrost can thaw according to forecasts. In addition to the temperature characteristics of the ground, construction according to this principle requires additional economic expenses for the preparation of the construction site. Also, the use of this principle does not allow fully guarantee the compliance of the design settlements and deformations of buildings during thawing with the actual ones.
At St. Petersburg State University of Railway Transport, in the department of "Buildings", there were calculated-theoretical studies, on the possibility of using reinforced concrete foundation platforms for the northern regions when using the II principle of construction. The results of these studies are reflected in [11]. In addition, the authors Abovsky N. P., Sidelev V. A., Popovich A. P., and others developed useful models of foundation platforms [12], [13], [14]. The peculiarity of these structures is their ability to absorb deformations that occur due to unstable soil and the action of seismic loading through a rigid spatial platform by the rigid connection of the upper and lower plates with a system of links, cross struts, and trusses.

Object of study
The object of the study is a single-floor section of a large-panel building with four aboveground residential floors and a technical attic (Fig. 1). The main load-bearing structures: a pile foundation with a high crossbar, external three-layer wall panels, internal reinforced concrete wall panels, reinforced concrete floor slabs.

Object modeling
The effectiveness of a large-panel medium-rise residential building with the proposed structural solution of the seismic isolation device was verified in the SCAD Office software and computational complex. The strength analysis of the considered structure was carried out based on the finite element method, by modeling the spatial calculation model of the building (Fig. 2) under the conditions of the inertial load of various intensities. The computational model was built using the following finite elements: • finite element No 44-plate finite elements that take into account shear tensile and compressive deformations, which were used to specify the exterior, interior wall panels, floor slabs, and strut; • finite element No. 55-elastic ties modeling the joints between the wall panels and the seismic insulation system with specified rigidity characteristics; • finite element No. 5 is a spatial rod modeling the pile heads and the piles themselves. Then the model was loaded with permanent, temporary, short-term and, special loads, and the calculation was made in two statements: -without taking into account seismic isolation; -about seismic isolation.
To analyze the results of the calculation, the seismic load was set for points 7 and 8 of category II soils.

Results
Based on the results of the studies performed, a structural solution of foundation structures in the form of a system with a seismic-isolating sliding belt (Fig. 3 and 4) is proposed for 5 E3S Web of Conferences 383, 02001 (2023) https://doi.org/10.1051/e3sconf/202338302001 TT21C-2023 buildings erected on the soil base according to the first principle (with permafrost preservation in the frozen state) in areas with a combination of various natural and climatic conditions-the presence of permafrost and seismic activity.
In this version, the seismic-isolating sliding belt consists of a stainless ground metal plate 300x300 mm in size and 20 mm thick, which is pre-mounted to the embedded parts of the head of each pile, as well as to the strut. Between the layers of plates is a layer of material with a low friction coefficient, the classical version -fluoroplastic F-4 according to GOST 10007 or its more modern analog-a woven material "naftlen", which has proved itself in the sliding devices of span structures. The size of antifriction material is taken on 100-200 mm, less than steel stainless plates.
The sliding belt structure is mounted on a reinforced concrete capping beam, which is erected after the piles are installed in their designed position. The option of reinforced concrete capping is traditional and has proven itself perfectly in the industrial construction of serial large-panel houses, in various areas of the Far North (Yakutsk-series 1-464VM and series 112, Norilsk-series 84).

Discussion / Analysis of results
Evaluation of the results of computational-theoretical research, presented in the form of a diagram of stress dependence on the intensity of earthquakes (Fig. 5), allows us to draw the following conclusions. When seismic isolation elements are taken into account in the calculation model, maximum stresses in the elements decreased almost twofold, which allows saying that the proposed solution is very effective from the point of view of increasing seismic resistance and safety of the building and the possibility of preventing its destruction. This option of increasing the seismic resistance of the object will reduce the stresses and forces that occur in the elements, which in turn will keep the supporting structures in working condition under seismic action. At the same time, in the analysis of the displacement diagram shown in Fig. 6, it is established that when taking into account in the calculation of seismic isolation, the displacements along the X-axis significantly increase (approximately 7.5 times). This indicates that with an increase in the flexibility of the building, the period of natural vibrations increases, and hence the displacement increases. 1625 As a consequence, to limit the displacements of seismically insulated parts of the building and prevent the growth of displacements, it is recommended to include additional damping devices in the building structure-dry or viscous friction dampers, limiters of horizontal and vertical movements, dynamic absorbers of vibration [15]. The placement of additional seismic protection devices can be carried out at the level of the basement floor or at the level of the technical floor, which is clearly illustrated in Fig. 7. 1-technical floor; 2-ground floor level.  The intensity of earthquakes, points X, мм Y, мм Z, мм

Movements without regard to seismic isolation
Movements taking into account seismic isolation