Walls according to constructive design. Constructive solutions for buildings with stone walls. by static function
Walls are the main load-bearing and enclosing structures of a building. They must be strong, rigid and stable, have the required fire resistance and durability, be low thermal conductivity, heat resistant, sufficiently air and soundproof, and also economical.
Basically, external influences on buildings are perceived by roofs and walls (Fig. 2.13).
The wall has three parts: the lower one is the plinth, the middle one is the main field, the upper one is the entablature (cornice).
Figure 2.13 External influences on the building: 1 - permanent and temporary vertical force impacts; 2 - wind; 3 - special force impacts (seismic or others); 4- vibrations; 5 - lateral soil pressure; 6- ground pressure (resistance); 7 - ground moisture; 8 - noise; 9 - solar radiation; 10 - precipitation; 11 - state of the atmosphere (variable temperature and humidity, presence of chemical impurities)
By the nature of perception and transmission of loads walls (external and internal) are divided into load-bearing, self-supporting and curtain walls (with a load-bearing frame) (Fig. 2.14). Load-bearing walls must ensure the strength, rigidity and stability of the building from the effects of wind loads, as well as loads on floors and coverings, transferring the resulting forces through the foundations to the base. Self-supporting walls must maintain their strength, rigidity and stability when exposed to loads from wind, their own weight and the overlying part of the wall. Curtain walls, intended only to protect premises from atmospheric influences (cold, noise), are constructed using highly efficient thermal insulation materials light multi-layered. They usually transfer the load (wind) within one panel and from their own mass to the elements of the supporting frame of the building.
By the nature of placement in the building a distinction is made between external walls, i.e. enclosing the building, and internal walls - separating rooms.
By type of materials used the walls can be wooden (logs, paving stones, frame-panel panels, etc.), made of stone materials, concrete, reinforced concrete, as well as multilayer (using highly effective heat-insulating materials as a heat-insulating layer).
The main parts of external walls are plinths, openings, piers, lintels, pilasters, buttresses, pediment, cornices and parapets (Fig. 2.14). Basement - the lower part of the wall adjacent to the foundation. The walls have openings for windows, doors and gates. The sections of walls between the openings are called piers, and those above the openings are called lintels. The crown cornice is the upper protruding part of the wall. Parapet is part of the wall enclosing the roof in buildings with internal drainage.
Figure 2.14 Wall structures: a - load-bearing in a frameless building; b - the same in a building with an incomplete frame; c - self-supporting; g - mounted; d - main parts of the walls; 1- foundation; 2 - wall; 3 - overlap; 4 - crossbar; 5 - column; 6 - foundation beam; 7 - strapping beam; 8 - base; 9 - opening; 10 - cornice; 1 - pier; 12 - jumper
In frame one-story industrial buildings, having large openings, significant height and length of the walls, to ensure their stability, half-timbering is used, which is a reinforced concrete or steel frame that supports the walls, and also absorbs the wind load and transfers it to the main frame of the building.
According to the design solution, the walls can be solid, or layered.
Walls are the most expensive structures. The cost of external and internal walls is up to 35% of the cost of the building. Consequently, the effectiveness of the structural design of the walls significantly affects the technical and economic indicators of the entire building.
When selecting and designing the wall structure of civil buildings, it is necessary to:
- reduce material consumption, labor intensity, estimated cost and cost;
- apply the most efficient materials and wall products;
- reduce the mass of walls;
- make the most of physical and mechanical properties materials;
- use materials with high construction and performance qualities, ensuring the durability of the walls.
In terms of thermal engineering, the enclosing parts of buildings must meet the following requirements:
- provide the necessary resistance to the passage of heat through them;
- not have a temperature on the inner surface that is significantly different from the indoor air temperature so that cold is not felt near the fences and condensation does not form on the surface;
- possessing sufficient heat resistance (thermal inertia) so that fluctuations in external and internal temperatures are less reflected in fluctuations in the temperature of the internal surface.
- maintain normal humidity conditions, as humidification reduces the heat-protective properties of the fence.
Brick walls. The materials for masonry are bricks: ordinary clay, silicate, hollow plastic pressed; hollow brick semi-dry pressed. (Fig. 2.15) When making a brick stack, their thickness can be different, depending on the climatic zone. So, in the conditions of Almaty, the wall thickness is 510 mm (2 bricks), and for internal load-bearing walls - 380 mm (one and a half bricks) and even 250 mm. Ceramic hollow stones and small concrete blocks (eg 490x340x388) can be used. Brick grades 50 - 150.
Ordinary clay brick is manufactured in dimensions 250x120x65 mm (88 mm) and has a volumetric mass of 1700 - 1900 kg/m 3.
Effective clay brick produced hollow and lightweight. The volumetric mass of hollow brick is 1300 - 1450 kg/m 3, lightweight brick is 700 - 1000 kg/m 3 or more.
Sand-lime brick has a volumetric mass of 1800 - 2000 kg/m 3 ; dimensions 250x120x65 (88 mm).
Slag brick has a volumetric mass of 1200 -1400 kg/m 3.
Hollow ceramic stones differ from hollow bricks in height dimensions (138, 188, 298 mm), shape and location of voids. Ceramic stones of plastic pressing with 7 and 18 voids and have dimensions 250x120x138 mm, volumetric mass 1400 kg/m 3
Lightweight concrete stones there are solid and hollow volumetric mass 1100 - 1600 kg/m3.
The dimensions of stones with slot-like blind voids are 190x390x188 and 90x390x188, three-hollow ones - 120x250x138 mm.
Stones with slot-like voids have the best thermal performance.
Facing bricks and stones are divided into profile and ordinary (solid and hollow).
Shaped ceramic slabs are either embedded or leaned.
In addition to ceramic products, concrete and other non-fired slabs and stones can be used for wall cladding. Natural stones and slabs from: natural stone is used for laying foundations and walls, for cladding (in the form of facing slabs - sawn, chipped, hewn, polished). Floors, window sills and stair steps are also made from natural stone. Solid masonry made from ordinary brick and heavy stone materials is used to a limited extent - where increased strength is required, as well as in rooms with high humidity. In other cases it is recommended; use lightweight masonry.
The masonry is carried out using heavy (sand) or light (slag) mortars of grade 10; 25 - 50 and 100.
Continuous masonry is carried out using a multi-row (spoon) or single-row (chain) seam dressing system; masonry of narrow walls (no more than 1.0 m wide) is the same as masonry brick pillars, is carried out according to a three-row system. The thickness of horizontal seams is assumed to be 12 mm, vertical 10 mm. For lightness and insulation, wells filled with lightweight concrete are left in the wall.
Figure 2.15 Walls made of brick and ceramic stones: a- single-row; b- multi-row; c - systems L.I. Onishchika; g - brick and concrete; d-well; e- with an air gap; f - s slab insulation; 1- poke; 2 spoons; 3- lightweight concrete; 4-air gap; 5-plaster; 6-board insulation; 7-grout.
Walls made of large blocks. Buildings from large blocks are constructed without frames and with frames (Fig. 2.16.). According to their purpose, large blocks are divided into blocks for external and internal walls, for walls of basements and plinths, and special blocks (eaves, for bathrooms, etc.). The material for large blocks is lightweight concrete with a class of at least B5 (slag concrete, expanded clay concrete, cellular concrete large-porous concrete, concrete on porous crushed stones) volumetric weight 1000; 1400 and 1600 kg/m3.
Concrete blocks for external walls they have a thickness of 300; 400 and 500 mm, for internal walls 300 mm. The outer surface of the blocks is textured with decorative concrete or facing tiles, and the inner surface is prepared for finishing.
Walls made of large panels. According to their design, the panels are divided into single-layer and multi-layer (Fig. 2.17). Single-layer panels are made from lightweight concrete with a volumetric weight of up to 1200 kg/m 3, which has the required frost resistance and heat-insulating qualities.
Multilayer panels (two-layer and three-layer) consist of a load-bearing shell that absorbs all loads and insulation. The outer surface of the panels can be textured with a 20mm thick decorative layer of white and colored cement, lined ceramic tiles and etc. Inner surface panels must have a finishing layer 10 mm thick.
The transfer of vertical forces in horizontal joints between panels represents the most difficult task of large-panel construction.
Figure 2.16.Large-block walls of civil buildings: a - two-, three- and four-row cutting of external load-bearing walls; b-main types of wall blocks; c - double-row cutting of self-supporting walls; I, II, III, IV - rows of blocks; d - diagrams of the arrangement of blocks in axonometry; blocks: 1- wall; 2 - jumper; 3 - window sill; 4-belt.
Figure 2.17 Panel walls civil buildings: Cutting of external walls: a- single-row with panels per room; b- the same for two rooms; c- double-row cutting of the panel structure; g-single-layer concrete; d - two-layer reinforced concrete; e - the same three-layer; g - from rolled slabs; 1- panel with an opening; 2- strip panel; 3- wall panel; 4 - reinforcement frame; 5 - lightweight concrete; 6 - decorative concrete; 7 - insulation; 8 - heating panel; 9 - reinforced concrete slab; 10 - rolled plate.
Four main types of connections have been used in practice (Fig. 2.18):
- platform joint, the peculiarity of which is that the floors are supported by half the thickness of the transverse wall panels, i.e. stepwise transmission of forces, in which forces are transmitted from panel to panel through the supporting parts of the floor slabs;
- serrated joint, which is a modification of a platform-type joint, provides deeper support for floor slabs, which, like a “dovetail,” rest across the entire width wall panel, but forces are transferred from panel to panel not directly, but through the supporting parts of the floor slabs;
- contact joint with the ceilings supported on remote consoles and direct transfer of forces from panel to panel;
- contact-socket the joint with the support of the panels is also based on the principle of direct transfer of forces from panel to panel and the support of the floors through consoles or ribs (“fingers”) protruding from the slabs themselves and placed in specially placed slots in the transverse panels.
Platform junction applied for all types of nine-story buildings, and also, as an experiment, in 17-story and 25-story buildings with a narrow pitch of transverse load-bearing walls.
Figure 2.18 Types of horizontal joints between load-bearing panels: a-platform; b-toothed; c- contact on remote consoles; g-contact-socket
A study of the old residential buildings of Moscow, St. Petersburg, Kaliningrad, Kaluga and other Russian cities showed that within the long-established central part of the city the main objects overhaul and reconstructions are two- to five-story residential buildings built at the beginning of the last century. The variety of structural forms of objects of the old stock is distinguished by a relatively small assortment: material - rubble stone, brick, wood; construction technology - manual labor.
Constructive solutions for old houses
Foundations in normal soils were, as a rule, built as strip foundations from torn rubble stone, or less often from burnt iron ore bricks with a complex mortar. On weak, unevenly compressed soils, for example, in St. Petersburg, foundations were often built on an artificial foundation - on wooden piles or beds.
Load-bearing walls of residential buildings were laid out on heavy cement and lime mortars made of solid red brick of the highest (by today's standards) quality. As a result, they have been preserved much better than other types of structures. The thickness of the walls ranges from 2.5 to 4 bricks. The rigid connection of the longitudinal and transverse stone walls of the buildings was ensured by installing hidden connections made of the strongest wrought iron. In general, civil buildings built before the revolution are characterized by a wide variety of design solutions and the presence of a significant number of transverse walls, ensuring high spatial rigidity of the load-bearing frame. The vertical load in these buildings is usually carried by external and internal longitudinal walls. Occasionally there are load-bearing wooden half-timbered partitions. Interior partitions They were made of wood (plastered on both sides with shingles) or brick.
The main type of floors in old stone buildings is the floor wooden beams with a roll of plates or boards. The pitch of load-bearing beams according to the pre-revolutionary “standard position” was usually assigned to 1-1.5 m. The floors in the living area are wooden, parquet or linoleum. In wet rooms and in the area of staircases and elevators - from metlakh tiles, or cement with iron reinforcement.
The rafter system of pitched roofs was made from layered logs and hanging type. The design of stairs in most stone buildings is made in the form of stone or concrete steps laid on steel stringers. In staircases with one stringer per flight, one end of the steps was embedded in the masonry of the walls.
Typification of design solutions of the old foundation
A number of research organizations are engaged in research and typification of design solutions in the field of major repairs and reconstruction of old residential buildings. The research results are summarized in unified system and sorted into groups and categories according to a variety of classification criteria.
In Fig.1. shows a schematic plan and section of a residential building with the designation structural elements and technical and economic parameters that are of greatest interest to designers and builders working in the field of reconstruction of old buildings.
Fig.1. Schematic plan and section of an old residential building with the designation of the main typification parameters
Analysis of the data accumulated by engineers and builders during the research process allows us to draw the following conclusions:
1. The most common is a two-span layout of residential buildings (with 1 internal wall), less often - a three-span layout (with 2 internal walls). The share of these schemes accounts for 53-54%, i.e. more than half of all houses.
2. The “clear” distance between load-bearing walls is:
- in Moscow from 4 to 7 m - 51%; from 7 or more - 46.9%;
- in St. Petersburg from 4 to 7 m - 77.1%; from 7 or more - 16.7%.
3. The most common distances between the axes of external walls:
- in Moscow from 2 to 2.5 m - 80.5%;
- in St. Petersburg from 1.75 to 2.75 m - 87.9%.
4. External walls in their upper part, at the level attic floor, have a thickness of 60 to 90 cm, and internal walls - from 40 to 80 cm.
5. The thickness of the ceilings and floors ranges from 33 to 40 cm (89.6%).
6. Floor heights also vary widely. However, in Moscow, buildings with floor heights from 3 to 4 m are 93.1%, and in St. Petersburg - 84.3%.
Reviewed design characteristics Old residential buildings should form the basis for the development of industrial engineering solutions.
Table 3.2 shows a diagram showing the dependence and variability of design solutions and methods for reconstructing old housing stock. In the practice of reconstruction work, which takes into account the physical wear and tear of non-replaceable structures, several solutions are used: without changing the structural design and with changing it; without changing the building volume, with the addition of floors and small extensions.
Table 3.2
The first option involves restoring the building without changing the building volume, but with the replacement of floors, roofing and other structural elements. In this case, a new layout is created that meets modern requirements and requests from social groups of residents. The reconstructed building must preserve the architectural appearance of the facades, and its operational characteristics must be brought up to modern regulatory requirements.
Options with changes in design schemes provide for an increase in the construction volume of buildings by: adding volumes and expanding the building without changing its height; superstructures without changing the plan dimensions; extensions of several floors, extensions of additional volumes with changes in the dimensions of the building in plan. This form of reconstruction is accompanied by redevelopment of premises.
Depending on the location of the building and its role in the development, the following reconstruction options are carried out: with preservation of residential functions; with partial repurposing and complete repurposing of the building’s functions.
Reconstruction of residential buildings should be carried out comprehensively, including, along with the reconstruction of the intra-block environment, its landscaping, improvement and restoration utility networks and so on. During the reconstruction process, the range of built-in premises is revised in accordance with the standards for the provision of primary care institutions to the population.
In the central areas of cities, buildings being reconstructed may house built-in citywide and commercial institutions of periodical and constant maintenance. The use of built-in spaces transforms residential buildings into multifunctional buildings. Non-residential premises are located on the first floors of houses located along the red building lines.
In Fig. 3.5 shows structural and technological options for the reconstruction of buildings with preservation ( A) and with change ( b,V) structural diagrams, without changing volumes and with their increase (superstructure, extension and expansion of the planned dimensions of buildings).
Rice. 3.5. Reconstruction options for early residential buildings A- without changing the design scheme and construction volume; b- with the addition of small volumes and the transformation of the attic floor into an attic; V- with the addition of floors and extension of volumes; G- with an extension of the building to the end of the building; d, f- with the construction of buildings; and- with extension of volumes of curvilinear shapes
A special place in the reconstruction of urban centers should be given to the rational development of underground space adjacent to buildings, which can be used as shopping centers, parking lots, small businesses, etc.
The main constructive and technological method for reconstructing buildings without changing the design scheme is to preserve the permanent structures of the external and internal walls, stairwells with the installation of heavy-duty floors. If there is a significant degree of wear and tear on the internal walls as a result of frequent redevelopment with the construction of additional openings, relocation of ventilation ducts, etc. reconstruction is carried out by installing built-in systems while preserving only the external walls as load-bearing and enclosing structures.
Reconstruction with a change in the building volume involves the installation of built-in permanent systems with independent foundations. This circumstance makes it possible to add several floors to buildings. In this case, the structures of external and, in some cases, internal walls are freed from the loads of the overlying floors and turned into self-supporting enclosing elements.
When reconstructing a building by widening it, constructive and technological options are possible for partially using existing foundations and walls as load-bearing ones with redistribution of loads from the floors being built on to the external elements of buildings.
The principles of reconstruction of buildings built later (1930-40s) are dictated by the simpler configuration of sectional type houses, the presence of floors made of small-piece reinforced concrete slabs or wooden beams, as well as the smaller thickness of external walls. The main methods of reconstruction consist in the addition of elevator shafts and other small volumes in the form of bay windows and inserts, the addition of floors and attics, and the construction of remote low-rise extensions for administrative, commercial or household purposes.
Increasing the comfort of apartments is achieved through complete redevelopment with replacement of floors, and an increase in the volume of the building as a result of the superstructure ensures an increase in the building density of the quarter.
The most typical methods of reconstruction of buildings of this type are the replacement of floors with prefabricated or monolithic structures with complete redevelopment, as well as an additional superstructure of 1-2 floors. In this case, the superstructure of buildings is carried out in cases where the condition of the foundations and wall fencing ensures the perception of changed loads. As experience has shown, buildings of this period allow for the addition of up to two floors without strengthening the foundations and walls.
In case of increasing the height of the superstructure, built-in building systems of prefabricated, prefabricated and monolithic structures are used.
The use of built-in systems makes it possible to implement the principle of creating large overlapping areas that facilitate the implementation of flexible room layouts.
From a thermal engineering point of view, there are three types of external walls based on the number of main layers: single-layer, two-layer and three-layer.
Single-layer walls are made of structural and thermal insulation materials and products that combine load-bearing and heat-protective functions.
In three-layer fences with protective layers on point (flexible, keyed) connections, it is recommended to use insulation from mineral wool, glass wool or polystyrene foam with a thickness determined by calculation, taking into account heat-conducting inclusions from bonds. In these fences, the ratio of the thicknesses of the outer and inner layers must be at least 1:1.25 at minimum thickness outer layer 50 mm.
In double-layer walls, it is preferable to place the insulation on the outside. Two options for external insulation are used: systems with an outer covering layer without a gap and systems with an air gap between the outer facing layer and the insulation. It is not recommended to use thermal insulation with inside due to the possible accumulation of moisture in the thermal insulation layer, however, if such use is necessary, the surface on the room side must have a continuous and durable vapor barrier layer.
When designing walls made of brick and other small-piece materials, lightweight structures should be used as much as possible in combination with slabs made of effective thermal insulation materials.
The course project adopts a load-bearing wall of a three-layer structure with a load-bearing layer of solid ceramic bricks 380 mm thick, concrete blocks or reinforced concrete (with a layer of internal plaster 20 mm), a layer of thermal insulation and a protective and decorative outer layer of brick 120 mm thick or lime-cement plaster 25 - 30 mm thick (Fig. 3.1). The coefficient of thermal uniformity without taking into account the slopes of openings and other heat-conducting inclusions is 0.95.
For the protective wall, ceramic face bricks or stones (GOST 7484-78) or selected standard ones (GOST 530-95), preferably semi-dry pressing, as well as sand-lime brick (GOST 379-95) can be used. When facing sand-lime brick the base, belts, parapets and cornice are made of ceramic bricks.
When facing, the brickwork is reinforced with the load-bearing part of the wall with welded reinforcing mesh, placed in height increments of 600 mm.
When the finishing layer is made of traditional thick-layer plaster with a thickness of 25 - 30 mm, thermal insulation boards are attached to the load-bearing layer of the wall using glue and additionally with spacer dowels.
External plaster is made from lime-cement mortar, prepared on site from lime, sand, cement, water and additives, or from ready-made mortar mixtures, and is reinforced with galvanized steel mesh in accordance with GOST 2715-75 with a mesh size of 20 mm and a wire diameter of 1 - 1.6 mm.
The reduced heat transfer resistance, m °C/W, for external walls should be determined in accordance with SNiP 23-02 for the facade of a building or for one intermediate floor, taking into account the slopes of the openings without taking into account their fillings, checking the condition of non-precipitation of condensation in areas in areas of heat-conducting inclusions.
Required thickness The thermal insulation layer should be determined taking into account the coefficient of thermal uniformity.
Thermal uniformity coefficient taking into account the thermal uniformity of window slopes and adjacent internal fences of the designed structure for:
Industrially manufactured panels should, as a rule, be no less than the values established in the table. 6;
For brick walls of residential buildings, as a rule, it should be at least 0.74 with a wall thickness of 510 mm,
0.69 - with a wall thickness of 640 mm and 0.64 - with a wall thickness of 780 mm.
Table 6
Minimum permissible values of the thermal homogeneity coefficient for industrially manufactured structures
Rice. 3.1. Structural solutions for external walls
1 – wall (load-bearing part); 2 – protective and decorative masonry; 3 – straightening gap; 4 – thermal insulation; 5 - interior plaster; 6 – external plaster; 7 – welded galvanized metal grid 20x20 Ø 1.0 – 1.6; 8 - adhesive composition for gluing thermal insulation boards; 9 – leveling plaster; 10 – embedded mesh; 11 - dowel
Example 1.
Perform thermal engineering calculations outer wall administrative building in St. Petersburg. The design of the outer wall is shown in Fig. 3.2.
Rice. 3.2. Calculation diagram of the outer wall
1 – cement-lime plaster; 2; 4 – brickwork; 3 – mineral wool plate “CAVITI BATTS”
Solution.
1. We determine the necessary initial data for thermal engineering calculations:
- calculated average temperature of the internal air of the building for thermal engineering calculations of enclosing structures - ˚С - the minimum value of the optimal temperature for premises of category 2;
Average outside air temperature during the heating period - °C - table. 1 SNiP 23-01-99;
Duration of the heating period - days - table. 1 SNiP 23-01-99;
Humidity conditions in the building premises – normal – table. 1 SNiP 23-02-2003;
Humidity zone for St. Petersburg - humid - adj. In SNiP 02/23/2003;
Operating conditions of enclosing structures – B – table. 2 SNiP 02/23/2003.
2. The normalized (required) reduced resistance to heat transfer of the fence structure is taken according to table. 7 depending on the number of degree days of the heating period or calculated according to
, m 2 o C/W, (2)
where and are the values determined from the table. 8;
– degree-day of the heating period, o C day, determined by the formula
, about S day, (3)
here is the estimated average temperature of the building’s internal air, ˚С;
The required heat transfer resistance of the wall is a function of the number of degree days of the heating period ( GSOP):
GSOP=D=(t in - t from. Lane) · Z from. lane ;
Where: t in– design temperature of internal air, o C;
t in= 20 o C – for premises of category 3a according to GOST 30494-96;
t from.lane, Z from.lane– average temperature, o C and duration, days. period with an average daily air temperature below or equal to 8 o C according to SNiP 23-01-99* “Building climatology”.
For St. Petersburg:
D= ·220=4796;
R tr =a·D+b=0.0003·4796+1.2=2.639 (m 2 o C)/W.
The thickness of the thermal insulation layer at l B= 0.044 W/(m o C) and the thermal uniformity coefficient r = 0.92 will be:
We take the insulation layer to be 80 mm, then the actual heat transfer resistance will be:
1. The construction project is a 16-story, single-section, large-panel residential building, built in the city of Kashira, Moscow region. Operating conditions for fences B according to SNiP 23-02.
2. External walls - made of three-layer reinforced concrete panels on flexible connections with polystyrene foam insulation 165 mm thick. The panels have a thickness of 335 mm. Along the perimeter of the panels and their openings, the insulation has protective layer from cement-sand mortar 10 mm thick. To connect reinforced concrete layers, two types of flexible connections made of corrosion-resistant steel with a diameter of 8 mm are used: triangular and point (studs). The calculation of the reduced heat transfer resistance was carried out according to formula (14) and the corresponding example of calculation in Appendix N.
3. To fill the openings, wooden window blocks with triple glazing in separate-paired frames.
4. Mineral wool insulation is used in the joints, sealed on the outside with Vilaterm sealant.
5. For the Moscow region (Kashira), according to SNiP 23-01, the average temperature and duration of the heating period are: . Internal air temperature =20 °C. Then the degree-days of the heating period according to formula (1) are
=(20+3.4) 212=4961 °C day.
Calculation procedure
1. According to Table 4 SNiP 23-02 =4961 °C day corresponds to the normalized heat transfer resistance for the walls of residential buildings.
2. The resistance to heat transfer of panels along the surface, calculated using formula (8), is equal to
3. The number of heat-conducting inclusions and thermal inhomogeneities in the walls of a 16-story building panel house include flexible connections, window slopes, horizontal and vertical joints of panels, corner joints, junction of panels to the cornice and basement floor.
To calculate the coefficients of thermal uniformity using formula (14) various types panels, the influence coefficients of heat-conducting inclusions and the areas of their influence zones are calculated based on solving problems of stationary thermal conductivity on the computer of the corresponding units and are given in
table K.1.
Table K.1
For the first floor
0.78·0.962=0.75;
For the last floor
0.78·0.97=0.757.
Reduced coefficient of thermal uniformity of the building façade
16/(14/0,78+1/0,75+1/0,757)=0,777.
The reduced resistance to heat transfer of the facade of a 16-story residential building according to formula (23) is equal to
Consequently, the external walls of a 16-story residential building meet the requirements of SNiP 23-02.
The foundation is the underground part of the building that absorbs all loads, both permanent and temporary, arising in the above-ground parts, and transfers these loads to the base. Foundations must meet the requirements of strength, stability, durability and efficiency. In this project, the foundation was chosen in accordance with the requirements of industrialization, achieved by using prefabricated blocks of factory or landfill production with their maximum consolidation, as far as the lifting and transport mechanisms available at the construction site allow.
This building is designed with a prefabricated reinforced concrete strip foundation for load-bearing and self-supporting walls. A strip foundation is a continuous wall, evenly loaded with overlying load-bearing and self-supporting walls and columns. Prefabricated strip foundations under the walls they are constructed from foundation blocks-pillows and from foundation wall blocks. The cushion blocks are laid on a layer of compacted sand 100 mm thick.
Cushion slabs for external walls are 1400 mm wide. Cushion slabs for internal walls are 1000 mm wide. Cushion slabs can be laid with gaps. At the junctions of the longitudinal and transverse walls, the cushion slabs are laid end to end and the junctions between them are sealed concrete mixture. Placed on top of the laid pillow slabs horizontal waterproofing and on top of it cement-sand screed 30 mm thick, in which they lay reinforcing mesh, which leads to a more uniform distribution of load from overlying blocks and structures.
Then the concrete is laid foundation blocks with ligation of sutures in five rows, on top of which a horizontal waterproofing layer from two layers of roofing felt on mastic. The purpose of the waterproofing layer is to prevent the migration of capillary ground and atmospheric moisture up the wall. The width of the foundation blocks for external walls is 600 mm. The width of the foundation blocks for internal walls is 400 mm.
The depth of the foundation or the distance from the planning mark of the ground to the base of the foundation is taken depending on the geological and hydrogeological conditions construction site, and on the climatic conditions of the area. The foundation depth of this building is 2.18 m, which exceeds the depth of soil freezing, which is 1.9 m in this area.
Exterior walls
In the construction of low-rise buildings, load-bearing frames are used that correspond to the types and properties construction materials and technologies for the construction of such buildings. This project uses a load-bearing frame with transverse and longitudinal load-bearing walls. The stability of walls, both load-bearing and bracing, is ensured by the rigid connection of longitudinal and transverse walls at their intersections and the connection of the walls with floors.
The walls of the building are designed to enclose and protect from the impacts environment and transfer loads from the structures above - floors and roofs - to the foundation.
Ordinary clay is used as a material for the walls of the building. solid brick. The walls are laid out of bricks with the gap between them filled with mortar. The mortar used is cement. The walls are laid with the obligatory observance of multi-row bandaging of seams. With a multi-row masonry system, dressing is carried out through five rows. Multi-row masonry is more economical than double-row masonry, as it requires less manual labor.
The project adopted lightweight well masonry with voids filled with mineral wool slabs. The partitions between the windows are reinforced with reinforcement meshes across 3 rows of masonry. Walls are erected by laying lightweight thermal insulation materials inside a stone wall - between two rows of solid walls. The thickness of the external walls is determined on the basis of thermal engineering calculations. The thickness of the external walls is 720 mm, the tie is 120 mm. This thickness is necessary to ensure resistance to wind and impact loads, as well as to increase the heat and sound insulation capacity of the walls.
Openings for windows and doors are provided with quarters. Quarters are installed in the side and upper lintels of external walls to ensure a tight, windproof connection of the filling elements - window and door frames. Doorways in internal walls do without quarters. The quarter is made by protruding the brick at the outer surface of the wall by 75 mm. The openings are covered with lintels that carry the load of the overlying masonry. Lintels are reinforced concrete bars or beams.
To protect the outer walls from moisture and to increase durability, a plinth is installed. The base is made of durable waterproof durable materials. The height of the plinth due to the presence ground floor, accepted - 0.85 m.
