Structural diagrams of buildings. Techniques for constructive solutions for buildings Reinforcement of slabs with a frame without crossbars

Monolithic frames are designed as frame or frame-braced (with the installation of monolithic stiffening diaphragms).

Depending on the solution of the crossbars (beams), monolithic frame-transom systems can be of two types: with main and secondary beams in different directions; with beams of the same value in two or three directions (with coffered ceilings).

In the first type of frame, the secondary beams rest on the main beams monolithically connected to them, and they, in turn, on the columns (see Fig. 5.3). The layout of the secondary and main beams in plan can be different (if they are located longitudinally or transversely ). When choosing the direction of the main beams, the purpose of the building, the spatial rigidity of the frame and other requirements are taken into account.

The spans of the main beams are 6-9 (12) m, the height of the cross section is 1/8-1/15 of the span, and the width is 0.4-0.5 of the height.

In each span of the main beam there are from one to three secondary beams. Secondary beams are also located along the axes of the columns. Their spans are 5-7 m, the cross-sectional height is 1/12-1/20 of the span, width is 0.4-0.5 of the height.

The spans of the monolithic floor slab are equal to the pitch of the secondary beams and amount to 2-3 m, and the thickness of the slab, depending on the load, is selected within 1/25-1/40 of the span and most often is 80-100 mm.

Fragments of sections

Rice. 5.3. 1 - column; 2 - main beam; 3 - secondary beam; 4 - monolithic floor slab

Frames with a frequent arrangement of beams (1-2 m) in two or three directions with the same pitch and height are called frames with coffered ceilings (see Fig. 5.4). Their advantages lie in the relatively lower height of the ceiling (beams) and high architectural expressiveness of the ceilings public buildings

Rice. 5.4. Monolithic reinforced concrete frames with caisson-type floors: a - structural and planning cells; b - section fragment

Among the promising ones are stacked superframe system(Fig. 5.5), in which the spatial rigidity of the building is ensured by the so-called superframe, which consists of several box-shaped pylons (trunks) connected to each other by powerful grillages at several levels along the height of the building. Multi-storey frames, which can have various planning and design solutions, rest on grillages (like shelves on whatnots). Frames of the stacked type are the most promising for very high-rise buildings (super-high-rise).

Rice. 5.5. Structural diagram of a shelf-type frame: a - facade diagram; b - diagram of a typical floor; c - grillage diagram; 1 - box pylon; 2 - grillage; 3 - frame-transom structure

Transomless frames

Transomless frame- a structural system with flat floors resting directly on columns without auxiliary beams.

Architecturally, transomless frames have significant advantages:

Flat floors have a total height that is 2-3 times less than floors in frame-transom systems;

Floors with smooth ceilings facilitate the use of free planning and transformation of premises by installing mobile partitions that are not rigidly connected to the floors;

Cantilever sections of floors along the perimeter allow for more complex configurations of facade planes, arranging loggias, terraces, verandas without additional structural elements;

The presence of a smooth ceiling allows you to avoid expensive suspended ceilings.

Transomless frames also have technical and economic advantages: the installation of formwork is simplified due to the absence of crossbars (with a monolithic production method), the area of ​​subsequent processing of the ceiling is reduced and finishing, laying pipelines under the ceiling, thermal insulation, etc. are simplified.

Along with the noted advantages, transomless systems have disadvantages that prevent their mass distribution in construction practice: the spans of beamless floors are more limited than in traditional transom systems; not in all cases the production of flat ceilings is cheaper and simpler than transoms; the calculation and assessment of the actual performance of floor structures is complicated.

However, these shortcomings, mainly of a constructive nature, can be eliminated with further improvement of the systems. The architectural qualities of transomless systems are increasingly attracting the attention of architects and designers. Numerous searches for specialists from different countries led to various design solutions. Many options for a transomless frame have been experimentally tested and entered into construction practice.

Several proposals for crossbar-less structures have been developed in Ukraine. Among them - mushroom frame, applied in projects of various types of public buildings (Fig. 12.79).

The mushroom-shaped frame fits into a structural grid based on an equilateral triangle with a side of 3.2 m and consists of two main elements: a column and a hexagonal floor slab. Each slab rests in the center on a column, forming a kind of fungus. Adjacent to each other with their side faces, the fungi are united into a honeycomb structure and, after welding and embedding, turn into a single spatial system. Thanks to the frequent spacing of the columns and the spatial work of the frame, the height of the slab ribs was increased to 15 cm, and the entire thickness of the floor with the floor structure was 20 cm.

From the hexagonal elements of the mushroom-shaped frame, you can create a wide variety of architectural and structural compositions. Despite the artistic merits, this type of frame has a serious planning drawback that limits its use. The frequent spacing of staggered columns makes it difficult to achieve functional solutions for most types of buildings, especially those with a wide body.

Modification of this system led to a version of the frame in which, along with the main floor slabs supported centrically on the columns, there are span slabs supported on the main (Fig. 12.79 b). The introduction of span floor slabs made it possible to dramatically increase the size of the triangular planning grid (from 3.2 to 6.6 m), which significantly improved the architectural qualities of the frame.

Rice. 12.79. Transomless mushroom-shaped frame with flat slabs (Ukraine): a - on a triangular grid of columns with a side of 3.2 m; b - on a triangular mesh with a side of 6.6 m; 1 - column; 2 - above-column (capital) slab; 3 - span slab; 4 - additional facade slab

Frame with cantilever-transom slabs(Fig. 12.80) designed for a 6 x 6 m planning grid and includes three main precast reinforced concrete elements - a column per floor, an over-column ribbed slab, asymmetrically supported by the column and the end of the adjacent slab, as well as an insert slab.

Advantages of the frame: simplicity of connections and installation of elements, the possibility of mutual displacement of rows of columns, i.e. transformation of the planning grid, and construction of buildings of complex configuration.

Rice. 12.80. Frame with cantilever-transom asymmetrically supported above-column slabs (Ukraine): a - general diagram; b - layout diagram of floor slabs; 1 - above-column slab; 2 - liner plate; 3 - cutting in places close to the lines of zero moments

Prefabricated monolithic system KUB-2.5(universal frame without crossbars) allows you to build residential buildings and public buildings in a single design key, using a single technology for the manufacture and installation of building structures. The system is a braced frame consisting of multi-storey continuous columns of rectangular section and solid floor slabs (Fig. 12.82). KUB-2.5 corresponds to the level of progressive modern industrial frame structures. A distinctive feature of the system is that the installation of floor slabs on a column and the connection of floor slabs to each other are carried out without supporting elements.

The design of the column joints eliminates welding, since the joint of columns with a cross section of 400x400 mm provides for forced installation, in which the fixing rod of the lower end of the column must enter the nozzle of the upper end of the lower column.

The frame structures assume a floor height of 2.8; 3.0; 3.3 m with a main grid of columns of 6x6 m. If necessary, the floor height can be increased to 6 m, and the column spacing - up to 12 m.

KUB-2.5 structures are used in the construction of public buildings of 1-3 floors with a large span with a technical underground and residential buildings of 4-22 floors.

Rice. 12.82. Prefabricated monolithic crossbar-less frame KUB-2.5: a - installation diagram; b - joint of columns; c - column-slab assembly

Monolithic frames without crossbars designed on the basis of a square or rectangular grid of columns, while the ratio between the larger and smaller spans is limited to 4/3. The most rational is a square grid of columns 6x6m.

In monolithic frames without crossbars, a solid reinforced concrete slab rests directly on columns with capitals (Fig. 12.83). Capitals ensure rigid connection of the slab with the columns and the strength of the slab against pushing along the perimeter of the column, and reduce the design span of the slab. The capitals of the columns are designed in the form of a truncated pyramid with an angle of inclination of the faces of 45° or a double truncated pyramid with a broken outline.

The thickness of the monolithic slab is taken from the condition of its required rigidity within 1/32-1/35 of the largest span. The slabs are reinforced with flat or rolled welded mesh. In this case, the span bending moments are perceived by the grids laid in the lower zone, and the supporting ones - in the upper zone of the slab.

One of the effective options for a monolithic crossbar-less frame for buildings with a fine-cell planning structure is the option with narrow columns in the form of short diaphragm walls without capitals (Fig. 12.84).

Columns of this type make it possible to use them as enclosing elements while simultaneously reducing the spans of slabs and increasing the rigidity of the frame. Columns can be not only flat, oriented in different directions on the plan, but also spatial (Fig. 12.84 b), logically fitting into the planning structure of the building.

This system is open and allows you to create a variety of space-planning solutions for residential, educational, administrative and other buildings with average spans of up to 7.5 m.

Rice. 12.83. Monolithic frame without crossbars: a - column capitals and their reinforcement; b - location of working reinforcement in the slab (plan); c - fragment of a section of the frame with an image of the slab reinforcement; 1 - working fittings; 2 - structural reinforcement

Rice. 12.84. Monolithic frame without crossbars with columns in the form of short diaphragm walls: a - fragments of the facade and plan of a corridor-type building; b - possible shapes of column sections; c - shapes of columns of variable cross-section in height

The structural system of a building is a set of interconnected load-bearing structures of the building, ensuring its strength, spatial rigidity and operational reliability. The choice of a building's structural system determines the static role of each of its structures. The material of structures and the technique of their construction are determined when choosing a building construction system.

The load-bearing structures of the building consist of interconnected vertical and horizontal elements.

Horizontal load-bearing structures - perceive all vertical loads falling on them and transfer them floor-by-floor to vertical load-bearing structures (walls, columns). Vertical structures, in turn, transfer the load to the foundation of the building.

Since ancient times, floor systems have been designed from a stereotypical approach to the layout of a beam cage, i.e. consisted of beams (crossbars) and flooring, which is how wooden floors are also structurally solved. Then reinforced concrete ribbed floor slabs appear, in which this approach is already merged into one structural element. The flat hollow-core floor slabs that appeared later are a significant step in the design of new types of building systems.

In industrial residential buildings, in comparison with traditional buildings that had mixed coverings that included fragments of wooden floors, horizontal load-bearing structures for the first time begin to play a role stiffness diaphragms In addition, floors perceive horizontal loads and impacts (wind, seismic, etc.) and transfer forces from these impacts to vertical structures.

The transfer of horizontal loads and impacts is carried out in two ways: either by distributing them to all vertical structures of the building, or to individual special vertical stiffening elements (walls, stiffening diaphragms, lattice wind braces or stiffening trunks). The industrial type of buildings also provides intermediate solutions - load transfer is possible with the distribution of horizontal loads in various proportions between stiffening elements and structures that work to absorb vertical loads.

Floors - rigidity diaphragms ensure the compatibility of horizontal movements of vertical load-bearing structures from wind and seismic influences. The possibility of compatibility and alignment of movements is achieved by rigid coupling of horizontal load-bearing structures with vertical ones.

As noted earlier, with a reduction in the construction volumes of buildings, the horizontal load-bearing structures of residential buildings with a height of more than two floors, in accordance with the requirements of fire safety standards, are made difficult to burn or non-combustible. These requirements, as well as the requirements of the economic stratum, are most fully satisfied by reinforced concrete structures, which determined their widespread use as horizontal load-bearing elements of all types of buildings. The floors are usually a reinforced concrete slab - prefabricated, precast, or monolithic.

Vertical load-bearing structures are distinguished by the type of structure, which serves as a defining feature for the classification of structural systems. On rice. 2 the main typological features of a residential building are given, the vertical load-bearing structures of which are continuous vertical plane of the walls. When using columns as the main vertical load-bearing elements of structures, already at the first stage of industrialization it was possible to obtain four structural schemes for a serial residential building: with a transverse arrangement of crossbars; with longitudinal arrangement of crossbars; with a cross arrangement of crossbars; crossbarless solution.

Industrialization made it possible not only to look at the work of floors from a new point of view, but also to significantly expand the typology of vertical load-bearing structures. With the development of serial housing construction, the following types of vertical load-bearing structures are distinguished in separate groups: block foundation frame development

planar (walls);

solid-section rods (frame struts);

volumetric-spatial (volumetric blocks);

volumetric-spatial internal load-bearing structures to the height of buildings in the form of thin-walled rods of an open or closed profile (stiffening trunks). The stiffening shaft is usually located in the central part of the building; Elevator, ventilation shafts and other communications are placed in the internal space of the shaft. In long buildings, several stiffening trunks are provided;

volumetric-spatial external load-bearing structures to the height of the building in the form of a thin-walled shell of a closed profile, which simultaneously forms the external enclosing structure of the building. Depending on the architectural solution, the outer load-bearing shell can have a prismatic, cylindrical, pyramidal or other shape.

According to the types of vertical load-bearing structures, five main structural systems of buildings are distinguished: frame, frameless (wall), volumetric block, trunk and shell, otherwise called peripheral

The choice of vertical load-bearing structures, the nature of the distribution of horizontal loads and impacts between them is one of the main issues in the layout of a structural system. It also influences the planning decision, architectural composition and economic feasibility of the project. In turn, the choice of system is influenced by the typological features of the designed building, its number of storeys and engineering and geological conditions of construction.

The spatial frame system is used primarily in the construction of multi-storey earthquake-resistant buildings with a height of more than nine floors, as well as in normal construction conditions if there is an appropriate production base. The frame system is the main one in the construction of public and industrial buildings. In residential construction, the scope of its use is limited not only for economic reasons. The basis of fire safety requirements when designing residential buildings is the consistent creation of vertical fire barriers - firewalls. In a frame-type structure, the creation of firewalls was carried out by embedding fireproof vertical rigidity diaphragms between the columns. Thus, the possibilities of spatial planning, the main advantage of frame systems, were limited in advance.

The frameless system is the most common in residential construction; it is used in buildings of various planning types with a height of one to 30 floors.

The volumetric block system of buildings in the form of a group of individual load-bearing pillars made of volumetric blocks installed on top of each other was used for residential buildings up to 12 floors high in normal and difficult soil conditions. The pillars were connected to each other by flexible or rigid connections.

The barrel system is used in buildings with a height of more than 16 floors. It is most advisable to use a barrel system for multi-story buildings that are compact in plan, especially in earthquake-resistant construction, as well as in conditions of uneven base deformations (on subsiding soils, above mine workings, etc.).

The shell system is inherent in unique high-rise buildings for residential, administrative or multifunctional purposes.

Along with the main structural systems, combined ones are widely used, in which vertical load-bearing structures are assembled from various elements - rod and planar, rod and barrel, etc.

A partial-frame system based on a combination of load-bearing walls and frame that support all vertical and horizontal loads. The system was used in two versions: with load-bearing external walls and an internal frame, or with an external frame and internal walls. The first option was used when there were increased requirements for freedom of planning decisions for the building, the second - when it was advisable to use non-load-bearing lightweight structures of external walls and when designing mid- and high-rise buildings.

The frame-diaphragm system is based on the division of static functions between wall (bracing) and rod elements of load-bearing structures. All or most of the horizontal loads and impacts are transferred to the wall elements (vertical stiffening diaphragms), and predominantly vertical loads are transferred to the rod (frame) elements. The system is most widely used in the construction of multi-storey frame-panel residential buildings under normal conditions and in earthquake-resistant construction.

The frame-barrel system is based on the division of static functions between the frame, which perceives vertical loads, and the trunk, which perceives horizontal loads and impacts. It was used in the design of high-rise residential buildings.

The frame-block system is based on a combination of a frame and volumetric blocks, and the latter can be used in the system as non-load-bearing or load-bearing structures. Non-load-bearing volumetric blocks are used to fill the load-bearing frame lattice floor-by-floor. The load-bearing ones are installed on each other in three to five tiers on horizontal load-bearing platforms (floors) of the frame, located in increments of three to five floors. The system was used in buildings above 12 floors.

The block-wall (block-panel) system is based on a combination of load-bearing pillars made of volumetric blocks and load-bearing walls, floor-by-floor connected to each other by floor disks. It was used in residential buildings up to 9 floors high in normal soil conditions.

The shaft-wall system combines load-bearing walls and a shaft with the distribution of vertical and horizontal loads between these elements in various proportions. It was used in the design of buildings above 16 floors.

The trunk-shell system includes an outer load-bearing shell and a load-bearing trunk inside the building, working together to absorb vertical and horizontal loads. The compatibility of the movements of the trunk and shell is ensured by horizontal load-bearing structures of individual grillage floors located along the height of the building. The system was used in the design of high-rise buildings.

The frame-shell system combines the outer load-bearing shell of a building with an internal frame, with the shell working for all types of loads and impacts, and the frame working primarily for vertical loads. The compatibility of horizontal movements of the shell and frame is ensured in the same way as in buildings of the shell-stem system. Used in the design of high-rise buildings.

The concept of “structural system” is a generalized structural and static characteristic of a building, independent of the material from which it is constructed and the method of construction. For example, on the basis of a frameless structural system, a building with walls made of chopped wood, brick, or concrete (large block, panel or monolithic) could be designed.

In turn, the frame system can be implemented in wooden, steel or reinforced concrete structures. Options also arose when using various materials to fill the cells formed by load-bearing elements in frame or barrel buildings. For this purpose, any elements were used - from small-sized to volumetric block ones.

The load-bearing part of a shell building can be a braced or unbraced spatial steel truss, a monolithic reinforced concrete shell with regularly spaced openings, a precast monolithic reinforced concrete lattice, and so on. Combined structural systems were also multivariate. The areas and scale of application of individual structural systems in construction were determined by the purpose of the building and its number of storeys.

Along with the basic and combined ones, mixed structural systems are used in design, in which two or more structural systems are combined in height or length of the building. This decision is usually dictated by functional requirements. For example, if it was necessary to make a transition from a frameless system in the upper standard floors to a frame system on the first floors, i.e. if necessary, install a fine-cell planning structure on standard floors above the hall planning structure on non-standard floors. Most often, this need arises when setting up large stores on the first floors of residential buildings.

A structural diagram is a variant of a structural system based on its composition and type of placement in space of the main load-bearing structures, for example, in the longitudinal or transverse directions. The structural design, as well as the system, is selected at the initial design stage, taking into account the space-planning design and technological requirements. In residential frame buildings, four structural schemes are used: with transverse or longitudinal crossbars, a cross arrangement of crossbars, and without crossbars.

When choosing a structural design for the frame, economic and architectural requirements are taken into account: the frame elements should not bind the planning solution; the crossbars of the frame should not intersect the surface of the ceiling in living rooms, etc. Therefore, a frame with a transverse arrangement of crossbars is used in multi-story buildings with a regular planning structure (mainly dormitories and hotels), combining the spacing of the transverse partitions with the spacing of load-bearing structures. A frame with a longitudinal arrangement of crossbars was used in apartment-type residential buildings.

A transom-less (beamless) frame in residential buildings was used only in the absence of an appropriate production base and large house-building plants in a particular region, since for prefabricated housing construction such a scheme is the least reliable and most expensive. The transomless frame was mainly used in the manufacture of monolithic and prefabricated monolithic building structures using the method of raising floors.

A building system is a comprehensive characteristic of the structural design of buildings based on the material and technology of construction of the main load-bearing structures.

Construction systems of buildings with load-bearing walls made of bricks and small blocks of ceramics, lightweight concrete or natural stone are traditional and fully prefabricated.

The traditional system is based on the construction of walls using hand-masonry techniques, as has been done in all traditional buildings since ancient times. It should be noted that in an industrial building, only enclosing structures, floors and other internal load-bearing structures remain traditional - they are completely identical to fully prefabricated structures.

The prefabricated system is based on the mechanized installation of walls from large blocks or panels made in a factory from brick, stone or ceramic blocks. With the introduction of new housing series, the large-block system is almost everywhere giving way to the panel system.

The traditional system (with wooden floors), which has long been considered the main type of capital civil building of medium and high-rise buildings, is a thing of the past. As has been repeatedly emphasized, structures based on a fire scenario were called “traditional.” Only for the convenience of classifying the huge variety of industrial structures, traditional buildings are distinguished among them, only in appearance reminiscent of the previous brick structures erected before the end of the 50s.

By the mid-80s of the last century, based on the use of the traditional system of enclosing structures, about 30% of the construction of residential buildings and 80% of mass public buildings were erected. Of course, the level of industrialization of building structures of the “traditional” construction system as a whole is quite high due to the massive use of large-sized prefabricated products for floors, stairs, partitions, and foundations.

The industrial traditional system had significant architectural advantages. Due to the small size of the main structural element of the wall (brick, stone), this system allows you to design buildings of any shape with different floor heights and openings of various sizes and shapes.

The use of the traditional system was considered most appropriate for buildings that dominate the development. The structures of buildings with hand-made walls are reliable in operation - high-tech fired bricks did not require the installation of time-consuming, short-lived plaster, and the fire resistance of industrial brick walls was significantly increased. When designing them, new approaches were used to ensure durability and heat resistance.

Along with the architectural and operational advantages, manual masonry of walls is the cause of the main technical and economic disadvantages of stone buildings: the labor intensity of construction and the instability of the strength characteristics of the masonry depending on different batches of bricks in the event of minor deviations in the technological process at brick factories. The quality and strength of the masonry depended on the season of construction and the qualifications of the mason.

The large-block construction system was used to construct residential buildings up to 22 floors high. The mass of the prefabricated elements was 3-5 tons. The installation of large blocks was carried out according to the basic principle of erecting stone walls - in horizontal rows, on mortar, with mutual bandaging of the seams.

The advantages of a large-block building system are: simplicity of construction technology, due to the self-stability of the blocks during installation, the possibility of wide application of the system in conditions of different raw material bases. The flexible system of block nomenclature made it possible to build various types of residential buildings with a limited number of standard sizes of products. This system required less capital investment in the production base compared to panel and block house construction due to the simplicity and lower metal consumption of molding equipment, and the limited weight of prefabricated products made it possible to use common installation equipment of low load capacity.

The creation of a large-block building system was the first stage in the mass industrialization of building structures with concrete walls. Compared to the traditional stone system, the large-block system reduced labor costs by 10% and construction time by 15-20%. With the introduction of a more industrial panel system, the volume of use of large-block systems is gradually decreasing. Already by the mid-70s of the last century, the large-block system in mass housing construction ranks third in terms of volume of use after panel and traditional stone systems.

The panel building system is used in the design of buildings up to 30 floors high in normal ground conditions and up to 14 floors in seismic areas. The introduction of the panel system into housing construction began in the late 1940s simultaneously in the USSR and France. In 1967, GOST 11309-65, developed by the USSR State Construction Committee, came into force for all types of large-panel houses, defining all the requirements for their quality, arrangement of joints and the degree of accuracy of production and installation of products.

The walls of such buildings are assembled from concrete panels one floor high, weighing up to 10 tons and 1-3 construction and planning steps long.

The technical advantage of panel structures is their significant strength and rigidity. This determined the widespread use of panel structures for high-rise buildings in difficult soil conditions (on subsiding and permafrost soils, above mine workings). For the same reason, panel structures demonstrate greater seismic resistance compared to other building systems.

In other economically developed countries, the volume of panel construction is also growing rapidly, which is explained by the high economic efficiency of the construction system. However, it should be noted that by the beginning of the 80s, no country had such a powerful industrial base in the construction industry, and by the mid-80s, most Western countries were affected by a serious economic crisis.

A frame-panel building system with a load-bearing prefabricated reinforced concrete frame and external walls made of concrete or non-concrete panels is used in the construction of buildings up to 30 floors high. Introduced in the USSR along with panel construction in the late 1940s, until the early 90s, about 15% of the volume of public buildings were built annually on its basis. In housing construction, the system was used to a limited extent, since it was inferior to the panel system in terms of technical and economic indicators.

The volumetric block construction system was also first introduced by Soviet builders. Volumetric block buildings are erected from large volumetric-spatial reinforced concrete elements weighing up to 25 tons, enclosing a living room or other fragment of the building. Volumetric blocks, as a rule, were installed on top of each other without ligating the seams.

Volumetric block construction allows you to significantly reduce the total labor costs in construction (by 12-15% compared to panel construction) and obtain a progressive structure of these costs. If in panel construction the ratio of labor costs at the factory and construction site is on average 50 to 50%, then in volumetric block construction it approaches from 80% of factory production to 20% of labor costs at the construction site. Due to the complexity of the technological equipment, capital investments in the creation of volumetric block house-building factories are 15% higher compared to panel house-building factories.

The volume-block system is used for the construction of residential buildings up to 16 floors high in normal and difficult soil conditions and for low- and medium-rise residential buildings with a seismicity of 7-8 points. Volume-block housing construction is most effective when there is a significant concentration of construction, the need to carry it out in a short time, and when there is a labor shortage.

The choice of one or another structural design of a building depends on its number of storeys, space-planning structure, availability of building materials and the base of the construction industry.

Structural diagram is a variant of a structural system based on the composition and placement in space of the main load-bearing structures - longitudinal, transverse, etc.

In frame buildings Three design schemes are used (Fig. 3.4):

With longitudinal arrangement of crossbars;

With transverse arrangement of crossbars;

Transomless.

Frame with longitudinal crossbar arrangement used in apartment-type residential buildings and mass public buildings with complex planning structures, for example, in school buildings.

Frame with transverse crossbar used in multi-storey buildings with a regular layout structure

Rice. 3.4. Structural diagrams of frame buildings:

a – with a longitudinal crossbar arrangement; b – with transverse; V -

without crossbar.

(dormitories, hotels), combining the pitch of transverse partitions with the pitch of load-bearing structures.

Transomless (beamless) frame, They are mainly used in multi-storey industrial buildings, less often in public and residential buildings, due to the lack of an appropriate production base in prefabricated housing construction and the relatively low efficiency of such a scheme.

The advantage of a non-transom frame is used in residential and public buildings when they are erected in prefabricated monolithic structures by lifting floors or floors. In this case, it is possible to arbitrarily install columns in the building plan: their placement is determined only by static and architectural requirements and may not obey the laws of modular coordination of steps and spans.

Variants of the frame structural diagram are presented in Fig. 3.5.

Fig. 3.5. Options for frame structural diagram:

A – with full; B – with incomplete; B – with a frame without crossbars; 1 – full frame with longitudinal crossbars; 2 – the same, with a transverse one; 3 – full frame with longitudinal arrangement of column crossbars (only at external walls) and long-span ceilings; 4 – incomplete longitudinal frame; 5 – the same, transverse; 6 – frame without crossbar; K – column; R – crossbar; J – vertical stiffness diaphragm; NP – flooring, NR – spacer flooring; I – load-bearing walls; II – curtain walls.

When designing buildings of the most common frameless system, the following five design schemes are used (Fig. 3.6):

scheme I– with a cross arrangement of internal load-bearing walls with a small pitch of transverse walls (3, 3.6 and 4.2 m). They are used in the design of multi-storey buildings, in buildings constructed in difficult soil and seismic conditions. Prefabricated floor structures used in mass construction, depending on the size of the span to be covered, are conventionally divided into small (2.4-4.5 m) and large (6-7.2 m) floors. ;

Fig.3.6. Structural diagrams of frameless buildings:

I – cross-wall; II and III – transverse wall; IV and V – longitudinal wall; A – options with non-load-bearing or self-supporting longitudinal external walls; B – the same, with load-bearing ones; a – plan of the walls; b – floor plan.

scheme II– with alternating sizes (large and small) of the pitch of transverse load-bearing walls and separate longitudinal stiffening walls (scheme with a mixed pitch of walls). Schemes I-II allow for a more varied solution to the layout of residential buildings, placement of built-in non-residential premises on the ground floors, and provide satisfactory planning solutions for children's institutions and schools;

scheme III – with sparsely spaced transverse load-bearing walls and separate longitudinal stiffening walls (with a large wall spacing). It has advantages when using fully prefabricated structures;

scheme IV – with longitudinal external and internal load-bearing walls and sparsely spaced transverse walls - stiffness diaphragms (every 25-40). They are used in the design of residential and public buildings of low, medium and high rises with stone and large-block structures. Rarely used in panel construction;

scheme V - with longitudinal external load-bearing walls and sparsely spaced transverse stiffening diaphragms. They are used in experimental design and construction of residential buildings with a height of 9-10 floors. Provides freedom in apartment planning.

One of the modifications transomless frame is a prefabricated monolithic frame or frame-braced frame with flat floor slabs, including multi-storey columns with a maximum length of 13 m of a square section of 40x40 cm, above-column, inter-column floor panels and insert panels of the same size in plan 2.8x2.8 m and a uniform thickness of 160 and 200 mm, as well as stiffness diaphragms.

Frame designed for the construction of relatively simple buildings in terms of composition with a height of up to 9 floors with a frame scheme and 16...20 floors with a frame-braced scheme with cells in a 6x6 plan; 6x3 m, and when introducing metal trusses onto cells 6x9; 6x12 m at height 3.0; 3.6 and 4.2 m with a full vertical load of up to 200 kPa and horizontal load from seismic influences of up to 9 points.

Monolithic and prefabricated glass-type foundations. External enclosing structures are self-supporting and suspended from various materials or standard industrial products of other structural systems. The staircases are predominantly made up of steps on steel stringers. The joints of the frame elements are monolid, forming a frame system, the crossbars of which are the floors.

The installation of structures is carried out in the following order: the columns are mounted and embedded in the glasses; install above-column panels with high precision, on which the quality of installation of the entire floor depends; Intercolumn panels are installed on the above-column panels. Then the insert panels are installed. After alignment, straightening and fixing of the floor, reinforcement is installed in the grouting seams and the seams between the panels and the joints of panels with columns are grouted throughout the entire floor.

Frame are calculated for the action of vertical and horizontal loads using the method of replacing frames in two directions. In this case, a slab with a width equal to the pitch of the columns in the perpendicular direction is taken as the frame crossbar.

When calculating the system for the action of horizontal forces in both directions, the full design load is taken, the bending moments from which are introduced in full in the design combinations. When calculating the system for the action of vertical forces, the work of the frame is taken into account in two stages: installation and operational. At the installation stage, hinged support of the floor panels is adopted in places of special mounting devices, except for the above-column panels, which are rigidly connected to the column. At the operational stage, frames are calculated for full vertical load in two directions. The calculated bending moments are distributed in a certain ratio between the spans and the above-column strips.

The force impacts on the columns at the bottom level of the floor panel are determined using formulas that take into account the two-stage operation of the structure. Elements of the structural system are prepared from class B25 concrete and reinforced with steel reinforcement of classes A-I; A-II and A-III.

A characteristic feature of the system is the interface between the above-column panel and the column. To effectively transfer the load from the panels to the column, the column is trimmed along the perimeter at the floor level with the four corner rods exposed. The collar of the over-column panel in the form of angle steel is connected to the rods using mounting parts and welding.

A connection unit for floor panels of the Perederia type joint, in which longitudinal reinforcement 0 12-А-П is passed through the bracket-shaped reinforcement outlets and monolid. To effectively transfer vertical loads, longitudinal triangular grooves are provided in the panels, forming a kind of key with the embedding concrete of the seam (200 mm wide) that works well for shearing.

The specified structural system is designed for use in areas with an underdeveloped prefabricated reinforced concrete industry for buildings for various purposes with relatively low requirements for the industrial indicator (degree of factory readiness) of the system. Fundamental solutions for a prefabricated monolithic frame without crossbars.

The technical and economic indicators of the system are characterized by slightly lower metal consumption than frame-panel systems for the same cell parameters, but higher concrete consumption and significant construction labor intensity.

IRKUTSK State Transport University

8. Korn G.K., Korn T.K. Handbook of mathematics for scientists and engineers. M.: Nauka, 1973. 831 p.

9. Van der Waerden. Algebra. M.: Nauka, 1979. 623 p.

10. Fikhtengolts G. M. Course of differential and integral calculus. T. 1. M.; St. Petersburg: Fizmatlit, 2001. 679 p.

11. Berezin I. S., Zhidkov N. P. Computational methods. T. 2. M.: GIFML, 1960. 620 p.

12. Krein M. G., Neimark M. A. Method of symmetric and Hermitian forms in the theory of separation of roots of algebraic equations. Kharkov: GTTI, 1936. 39 p.

UDC 699.841 Shcherbin Sergey Anatolyevich,

Ph.D., Associate Professor, Dean of the Faculty of Technical Cybernetics, Angarsk State Technical Academy, e-mail: [email protected]

Chigrinskaya Larisa Sergeevna, senior lecturer of the department of industrial and civil engineering, Angarsk State Technical Academy, e-mail: [email protected]

SIMULATION OF STRENGTHENING THE SUPRACOLUMN JOINT

WITHOUT BEAM FRAME

S.A. Shcherbin, L.S. Chygrynskaya

BEAMLESS FRAMEWORKS ABOVE COLUMN JOINT STRENGTHENING MODELING

Annotation. The article discusses various options for strengthening the above-column joint of a beamless floor. Modeling of reinforced joints was carried out in the SCAD environment, analysis and comparison of numerical calculation data was carried out in order to select the most rational reinforcement option.

Key words: modeling, strengthening, supra-column joint; beamless frame, beamless ceiling.

Abstract. Various options of strengthening above-column the joint of beamless flat slabs are considered. Analysis and comparison of the numerical calculation data in the SCAD program are executed.

Keywords: modeling in SCAD, strengthening, beamless flat slab, stress and deformation distribution.

Over the first decade of the 21st century in Russia, many norms and rules in the field of construction have undergone significant changes.

As a result, a large number of both operational and unfinished buildings, designed according to previous standards, do not meet modern requirements.

The current situation requires an assessment of the load-bearing capacity and suitability for normal operation of the structures of existing buildings, as well as the search for new options for strengthening the structural systems used in construction.

stem (KS).

In Russia, systems with a transomless frame have become widespread, characterized by speed of construction, architectural expressiveness and free internal layout of premises while ensuring the strength, reliability and stability of the building.

There are a large number of scientific publications on the problems of using CS with a frameless frame in construction practice, but there is very limited information on experimental studies of the operation of such systems under load, and there are no clear recommendations for ensuring the spatial rigidity of the building. In addition, the known CS have significant disadvantages - complex technology and, accordingly, the complexity of making joints between slabs and above-column joints, which often leads to a decrease in the reliability of the system.

Therefore, it seems relevant to experimentally study the stress-strain state of a beamless floor in order to find effective options for increasing the reliability and seismic resistance of buildings.

As a result of full-scale tests of a structural cell of a beamless floor built into the KUB-1 frame system, an uneven distribution of deflections was revealed

Modern technologies. Mathematics. Mechanics and mechanical engineering

and violation of the regularity of the floor stress fields in the areas of interface between the above-column panels and the frame posts and, accordingly, insufficient and different rigidity of the above-column joints.

The identified problems indirectly indicate a violation of the technology for making joints on a construction site, since in the frame of the KUB-1 system all interfaces of structural elements must have the same rigidity.

Accordingly, at the next stage of work there was a need to develop new technical solutions to strengthen the above-column joint of transomless frames.

According to the design documentation for the construction of buildings and structures according to the KUB series, the capless joint of floor slabs with columns (Fig. 1) is carried out by welding special metal elements with subsequent embedding of the mounting units. The hole in the columnar plate is framed with a rolled angle.

Several variants of the modified supracolumn joint have been developed (Fig. 2). In the 1st option (Fig. 2, a) it is proposed to install a metal clip from a rolled angle at the top and bottom of the above-column joint (it is possible to install the clip only at the top - option 1*). The corners are attached to the embedded parts of the slab by welding, and to the column with anchor bolts or studs. In the 2nd option (Fig. 2, b), the existing unit is strengthened by adding horizontal reinforcement bars laid in mutually perpendicular directions on top of the slab and passing through the column. The 3rd option (Fig. 2, c) involves the installation of an upper frame consisting of rolled angles anchored from the column to the slab.

To compare the effectiveness of the presented reinforcement options in terms of unloading the unit by reducing the perceived forces, computer modeling and calculations of the strength and deformation of above-column joints were performed using the SCAD computer complex for constant and temporary uniformly distributed loads. The stress isofields arising in the above-column part of the slab, taking into account the reinforcement according to option 1 and without it, are shown in Fig. 3, 4. The obtained values ​​of slab deflections in the above-column and cantilever parts, normal and tangential stresses arising in the above-column joint at the top and bottom of the beamless floor are given in Table. 1.

Mont azh about I "give them, but"

Mounting assembly 5 case / tensile forces

Rice. 1. The joint of the above-column floor slab with the column: 1 - embedded part connecting the column rod with the embedded part of the above-column slab; 2 - concrete monolithic sealing

Rice. 2. Options for strengthening the supra-column joint

Rice. 3. Stress isofields N (t/m) in the above-column part of the serial unit slab (without reinforcement)

Rice. 4. Stress isofields N (t/m) in the above-column part of the slab of the unit, reinforced according to option 1

Table 1

Comparison of methods for strengthening the supracolumn joint

Parameter Node

without amplification 1 1* 2 3

2nh, mm -0.28 -0.17 -0.21 -0.23 -0.19

Zк, mm -0.74 -0.51 -0.59 -0.64 -0.61

dt low, top g/m2 " 137-161 135-159 137-160 116-136 133-156

DT low, low t/m2 -144-168 -147-170 -137-160 -134-155 -137-160

LF, top t/m2 225264 147173 169200 187220 218254

LF, bottom 1\u. t/m2 ​​-237-276 -158-184 -197-228 -212-245 -210-245

dt low, top t/m2 " 67 44 62 57 48

dt low, bottom t/m2 -67 -49 -44 -56 -44

Thunch, t/m2 ±(85-100) ±(14-17) ±(28-37) ±(70-82) ±(74-87)

/R. аРм t -1.05 -0.79 -0.86 -0.91 -0.86

O r.arm t +0.43 +0.26 +0.34 -0.35 -0.27

OD, t 0 0 -0.07 -0.02 -0.03

Notes:

GTICH GUKCH

Z, Z - vertical displacement of the slab in the above-column and cantilever parts;

The forces are taken when loading “own weight + live load”;

For steel C245 I = 240 MPa = 24465 t/m2;

Yxt - stresses in the material in the above-column part of the slab (top of the slab - tension; bottom of the slab - compression);

- ^ arm - longitudinal force in the working reinforcement of the column;

Or-arm - shearing force acting on the working reinforcement of the column;

Force in the inserted embedded part in the body of the floor slab;

In nodes 1 and 1*, the reinforcement corner is modeled by a plate, i.e., only one corner flange.

Analyzing the data in table. 1, the following can be noted:

Efforts (№■ arm and have the smallest absolute values ​​for option 1 reinforcement. Accordingly, its use will increase the degree of static indetermination of the

structure and will lead to a redistribution of forces when loading a beamless slab, the formation of plastic hinges and a reduction in the vertical load on the column;

The greatest reduction in deformations ^nch, Zkch) and, consequently, a decrease in stresses in the slab material (M„ N, N Txy) is also observed for option 1.

Data for comparing methods of reinforcement based on the force factors that arise in the reinforcement elements (Table 2) can be used for a reasonable selection of the sizes of reinforcing elements, reducing material consumption and costs for strengthening the above-column joint.

Table 2 Comparisons of options by power factors

in reinforcement elements

Parameter Node, reinforcement element

1, angle clip at the top and bottom of the slab 1*, angle clip at the top of the slab 2, reinforcing bars 3, angle clip with anchor

Z, mm -0.15 -0.17 - -

N, t - - 1.14 1.22

N/, t/m2 1003-1765 1369-2160 - -

N/, t/m2 1007-1772 1373-2167 - -

Qz, t - - -0.17 +0.39

My, tm - - ±0.01 ±0.02

Accordingly, based on the results of comparison of options, for reasons of efficiency in reducing force factors in the above-column part and the labor intensity of implementing reinforcement elements, option 1 is the most preferable. The use of this method of reinforcement will lead to an increase in the rigidity of the horizontal disk of the floor and an increase in the seismic resistance of the structural system of the transom-less frame.

BIBLIOGRAPHICAL LIST

1. Chigrinskaya L. S., Berzhinskaya L. P. Analysis of the use of transomless frames in seismic areas // Construction complex of Russia: science, education, practice: materials of the international. scientific-practical conf. Ulan-Ude: Publishing house of the All-Russian State Technical University, 2008. pp. 60-63.

2. Guidelines for the design of reinforced concrete structures with beamless floors. M.: Stroyizdat, 1979. 65 p.

3. Guide to the calculation of statically indeterminate reinforced concrete structures. M.: Stroyizdat, 1975. 189 p.

4. Chigrinskaya L. S., Kiselev D. V., Shcherbin S. A. Study of the work of a structural cell of a beamless ceiling of the KUB-1 system // Vestnik TGASU. 2012. No. 4 (37). pp. 128-143.

UDC 622.235:622.274.36.063.23 Tyupin Vladimir Nikolaevich,

Doctor of Technical Sciences, Professor of the Department BZD and ZS, ZabIZHTIRGUPS, tel. 89144408282, e-mail: [email protected]

Svyatetsky Viktor Stanislavovich,

General Director of JSC Priargunsky Industrial Mining and Chemical Association,

tel. 83024525110

METHODOLOGY FOR DETERMINING PARAMETERS OF DRILLING BLASTS DURING MINING OF LOW-POWER URANIUM ORE BODIES IN ORDER TO REDUCE DILIFICATION

V.N. Tyupin, V.S. Sviatetsky

METHODS OF BORING-BLASTING RATINGS DETERMINATION IN THE LOW-POWERED URANIUM ORE-BODIES MINING FOR THE PURPOSE OF INCREASING THE USEFUL COMPONENT IN THE BULK

Annotation. The mechanism and zones of action for the explosion of borehole explosive charges in a fractured rock mass, and the dependencies for determining the parameters of explosive explosives in chamber versions of systems for mining low-power uranium ore bodies are presented. The use of chamber mining options will increase productivity

production and reduce ore dilution compared to downward layered excavation with hardening backfill.

Key words: thin ore bodies, chamber mining systems, explosion zone mechanism, drilling and blasting parameters, dilution.