Monolithic columns are part of a building, vertical load-bearing elements. They lean on the columns balconies, terraces, ceilings. In addition to their main functions, columns are decorative element, decorate entrance group buildings and facade.
Columns receive and transmit the load from the elements above to the foundation of the building. Reinforced concrete pillars connect the structure and serve as support for the floors.
The architectural term "column" refers directly to the middle part, support pillar . The protrusions at the top of the post for supporting floors or crossbars are called capitals or consoles. Sometimes there is a column support, a glass for attaching to a columnar foundation.
Species and types
Concrete columns are divided by type of section, production method.
According to the type of section they are divided square, round or rectangular form.
Classified according to production method factory-ready elements, supplied to the site ready-made structures or erected on construction site, monolithic columns.
Features of the construction of monolithic columns
Before carrying out work, prepare the site, necessary materials, tools, structures. The site is marked.
Then they move directly to construction:
- assemble formwork;
- install the reinforcement frame;
- pour the concrete mixture;
- carry out concrete maintenance procedures;
- allow time for the mixture to gain strength;
- demoulding structures.
Monolithic reinforced concrete columns calculated at the design stage. The cross-section and shape of the column, the diameter of the reinforcement, and the brand used will depend on the amount of the planned load, including the element’s own weight.
Important! Installation deficiencies and miscalculations lead to the destruction of the structure. If the cross-section is insufficient, longitudinal bending deformation occurs and the column bends under load.
Preparation of tools and materials
The need for materials and tools is clarified at the stage of preparation for work. Tools you will need:
- metal square, level for checking the verticality and horizontality of surfaces;
- steel rod, will help release air;
- screwdriver for fastening formwork;
- vibrator compacts the mixture;
- prefabricated formwork from shields, supports.
The concrete mixture is delivered to the construction site ready-made or mixed immediately before laying using a concrete mixer. To prepare, take one part of cement, add two parts of sand, mix with two parts of crushed stone and two parts of gravel. By mixing the dry mixture with water, plastic concrete of a uniform consistency is achieved.
Except concrete mixture The following materials are needed:
- nails, self-tapping screws for fastening formwork;
- reinforcing bars of design cross-section and length;
- steel wire;
Installation of formwork
The formwork is installed in the design position. The shields are aligned vertically and strengthened with the help of struts, wooden struts. The struts are anchored using support blocks in two directions to prevent shifting.
When concreting a high column, the formwork installation process is somewhat different from the usual one. Three sides of the form are mounted, and the fourth side is closed as the formwork is filled with concrete.
Reinforcement
By tying the rods together, you get rigid volumetric frame to strengthen concrete. The number of longitudinal rods in the frame is 4-6 pcs. For a square section, four rods at the corners of the element are sufficient, for rectangular shape the long side is further reinforced. Cross-linking of reinforcement is used when constructing columns up to 2 meters long.
A frame exceeding a length of 2 m is tied with short rods across, in increments of 20-50 cm, taken in the calculation according to the planned load.
The capitals are reinforced with reinforcing mesh.
The thickness of the mesh rod is 15 mm, the cell size is 10 x 10 cm.
Reinforcement of the column is carried out by laying a mesh in each step; the dimensions and number of meshes are taken from the project.
Concreting
After installation of the formwork and reinforcement cage start concreting, which produced in layers, in layers 0.3-0.5 m thick, preventing the previous layer from setting. Do not add 50-70 mm of mortar to the top of the formwork.
To shrink concrete in columns above 5 meters, arrange technological breaks from 40 minutes to 2 hours.
When feeding ready-mixed concrete by mechanization, the feed speed is reduced to avoid segregation. Air is removed from the mixture steel rods, concrete compacted with manual vibrators. In places inaccessible to the vibrator, concrete is compacted manually by careful bayoneting.
Upon completion of work, they produce seasonal care behind the concrete.
Dismantling of formwork
Time required for concrete to reach 100% working strength is 28 calendar days. The indicator may vary depending on environmental conditions - temperature, humidity, care package. The average standing period for monolithic columns before stripping is 7-10 days. summer period. This period allows the corners and side edges to form.
note
Until the concrete reaches 100% strength of monolithic columns, work is suspended or related work is carried out. The load on the uncured mortar will lead to the destruction of structures.
Removal of the formwork begins with the struts, gradually removing the fastenings and side panels.
Monolithic columns as a frame element provide spatial rigidity and strength of the building.
Useful videos
Formwork for columns and their filling:
See how the reinforcement frames of the columns are knitted:
Rules for installing small-panel formwork for pouring a monolithic concrete column for a private house, see:
Concreting process monolithic frame columns of the house, look:
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Reinforced concrete frame of one-story industrial buildings
The reinforced concrete frame of one-story buildings includes a system of foundations, columns, rafters and under truss structures(if the pitch of the columns is greater than the pitch of the rafter structures), crane and frame beams, as well as stiffeners. The transverse frame of the frame is formed by columns, which are rigidly connected to the foundation and hinged to rafter structures (beams or trusses), the upper chords of which are untied by the system horizontal connections(in purlin coverings) or a continuous slab covering (Fig. 1).
Rice. 1. Fragment of reinforced concrete frame
Foundations
Based on the method of construction, foundations are divided into monolithic and prefabricated.
As a rule, they install under the columns of a frame building columnar foundations with glass-type pillars, and the walls rest on foundation beams. Strip and solid foundations are rarely provided, as a rule, on weak, subsiding soils and with large impact loads on the soil of technological equipment.
Unified monolithic reinforced concrete foundations They have a stepped shape with a glass-type column support for embedding columns (Fig. 2).
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section of the column
Fig.2. General view of a step-shaped monolithic foundation with a glass-type sub-column under the outermost column
Prefabricated foundations are more economical than monolithic ones, but they consume more steel. Lighter and more economical in terms of steel consumption are prefabricated foundations of ribbed or hollow structure.
When the level is close groundwater(GWL) and for weak soils they are suitable pile foundations. The most common reinforced concrete piles are round and square sections. The top of the pile is connected with a monolithic or prefabricated reinforced concrete grillage, which also serves as a column support.
The column support is installed on the slab layer by layer cement-sand mortar. When a bending moment is applied to the foundation, the connection between the column support and the slab is strengthened by welding the embedded elements, and the welding points are sealed with concrete.
The slab steps of all foundations have a single unified height of 300 mm or 450 mm.
At the top of the column there is a glass for installing a column into it. The bottom of the glass is placed 50 mm below the design mark of the bottom of the column in order to compensate for inaccuracies in the dimensions and laying of the foundations by adding mortar.
Columns are connected to the foundation different ways. Mainly using concrete. To ensure rigid fastening of the column in the foundation shell, horizontal grooves are arranged on the side surfaces of the reinforced concrete column. The gap between the edges of the column and the walls of the glass at the top is 75 mm, and at the bottom of the glass is 50 mm (Fig. 2).
The edge of the foundation for reinforced concrete columns is placed at the level of -0.15 m, for steel columns - at the levels of -0.7 m or -1.0 m.
Foundations for adjacent columns in expansion joints are made general, regardless of the number of columns in the node. In this case, a separate glass is installed for each prefabricated reinforced concrete column (Fig. 3).
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Rice. 3. Monolithic reinforced concrete foundations
columns in places of installation expansion joints
In foundations for steel columns, the subcolumn is made solid (without a glass) with anchor bolts (Fig. 4).
a) b)
Rice. 4. Monolithic foundations for steel columns:
a) columns of constant cross-section;
b) two-branch columns (through section)
The walls of frame buildings rest on foundation beams, laid between the foundation pillars on concrete columns of the required height, concreted on the ledges of the foundations (Fig. 2). Foundation beams have a T-shaped or trapezoidal cross-section (Fig. 5). Their nominal length is 6 and 12 m. The structural length of the foundation beams is selected depending on the width of the column and the location of the beams. The top edge of the beams is located 30 mm below the finished floor level.
Rice. 6. Detail of the basement of a one-story industrial building
Reinforced concrete columns
Columns in the frame system carry vertical and horizontal permanent and temporary loads. Designed for mass industrial construction standard designs prefabricated reinforced concrete columns for buildings with supporting overhead cranes and for craneless buildings.
Reinforced concrete columns for buildings with overhead cranes have consoles for supporting crane beams. For craneless buildings, columns without consoles are used.
Based on their location in the building system, columns are divided into extreme (located at the outer longitudinal walls), middle and end (located at the outer transverse (end) walls).
For craneless buildings with a height of 3 to 14.4 m, columns of constant cross-section have been developed (Fig. 7). The cross-sectional dimensions of the columns depend on the load and length of the columns, their pitch and location (in the outer or middle rows) and can be square (300x300, 400x400 mm) or rectangular (from 500x400 to 800x400 mm). They are buried into the foundations by 750 - 850 mm.
Rice. 7. Types of reinforced concrete columns for craneless buildings
For buildings with supporting bridge cranes of light, medium and heavy operating modes and a load capacity of up to 300 kN, columns of variable cross-section with a height of 8.4 to 14.4 m have been developed (Fig. 8), and for buildings with cranes with a load capacity of up to 500 kN, two-leg columns with a height of 10.8 to 18 m (Fig. 9).
The dimensions of columns of variable cross-section in the crane part range from 400x600 to 400x900 mm, in the over-crane part - 400x280 and 400x600 mm. The two-branch columns have dimensions in the crane part of 500x1400 and 500x1900, and of individual branches - 500x200 and 500x300 mm.
Rice. 8. Types of solid reinforced concrete columns for buildings with
overhead support cranes
Rice. 10. Two-branch reinforced concrete columns
with passages at the level of the crane tracks
Reinforced concrete columns contain steel embedded elements for fastening rafter structures, crane beams, wall panels(in the outer columns) and vertical connections(in tie columns). In places where truss structures and crane beams are supported, anchor bolts are passed through steel sheets.
In buildings with rafter structures, the length of the columns is taken to be 600 mm less (see Fig. 8,9,10).
Half-timbered columns
In addition to the main columns, the buildings are equipped with half-timbered columns installed at the ends of the buildings and between the main columns of the outer longitudinal rows at a pitch of 12 m and a length of wall panels of 6 m. They are designed to absorb wind forces and the mass of the walls.
The half-timbered columns are hingedly attached to the foundation by welding the embedded parts of the column and the support sheet installed on top of the foundation strictly along the axes (node 2, Fig. 11). The half-timbered columns are attached to the covering structures using a sheet hinge (node 1, Fig. 11). This connection ensures the transfer of wind loads to the building frame and eliminates the vertical impacts of the coating on the half-timbered columns.
Unified reinforced concrete columns for end fencing of two types (I and II) are used in the cases given in Table 1. In other cases, steel fencing columns are used. The designs of the columns are shown in Fig. eleven.
When designing columns, it is necessary to comply with structural requirements: the dimensions of the column sections must provide such flexibility that they do not exceed the ratio in any direction .
For a building with overhead cranes, the cross-sectional dimensions of the over-crane part of the outer columns are determined based on the conditions for placing crane equipment. The section height is 380 and 600 mm for solid columns. For the crane part of solid columns, the section height increases accordingly to 600...900mm.
The cross-sectional width of the column bс is taken from the manufacturing technology to be constant over the entire height of the column: for columns of the outer and middle rows with a step in the longitudinal direction B=6m - no less than 400mm; at H=12m - no less than 500 mm. In addition, based on the rigidity requirements bс(1/25)Н, Н is the height to the bottom of the rafter structure.
All columns are provided with embedded parts for installing rafter structures, wall panels and crane beams.
For the manufacture of columns, welded frames are used with working longitudinal reinforcement made of class A-III steel with a diameter of 16 mm, and transverse rods are made of steel classes A-I or Vr-I. When using high-strength concrete of classes B45...B60, it is advisable to reinforce the columns using non-tensioned reinforcement of classes A-IV and A-V, which allows reducing the consumption of metal by 20...40% and concrete by up to 20%.
In addition, from design experience it has been established that in flexible columns it is possible to use prestressed reinforcement of classes A-IV and A-V, which makes it possible to increase the rigidity and crack resistance of columns, improve the conditions for transporting long columns, as well as reduce transverse reinforcement and mechanize reinforcement work. In such columns, compared to columns made of conventional reinforced concrete, steel consumption is reduced by up to 40% and cost by up to 10%.
Columns of one-story industrial buildings are subject to all requirements for the design of compressed elements. The thickness of the protective layer of concrete for working longitudinal reinforcement is taken to be at least 20 mm and not less than the diameter of the rod; for transverse reinforcement - not less than 15 mm and not less than the diameter of the transverse rod.
Longitudinal bars in reinforcement products at the ends must have protective layer concrete of at least 10 mm for a column length of up to 18 m and at least 15 mm for a column length of more than 18 m. for transverse bars of reinforcing products, the ends must have a protective layer of at least 5 mm.
Longitudinal working reinforcement is placed along the edges perpendicular to the bending plane of the column and concentrated in the corners of the section. If the distance between the axes of the working rods in the direction of the bending plane is more than 500 mm, it is necessary to install structural reinforcement with a diameter of at least 12 mm so that there is no more than 400 mm between the longitudinal rods.
Overlapping joints of longitudinal rods (without welding) are provided in places where the column cross-section changes, ensuring the length of the anchorage. In this case, in a stepped column, the longitudinal reinforcement of the crane part is brought beyond the edge of the spacer, also ensuring the length of the anchorage.
The diameter of the transverse reinforcement is assigned depending on the type of reinforcement cage and the largest diameter of the longitudinal working reinforcement and must be at least 0.25d (d - largest diameter working longitudinal reinforcement), and in knitted frames, in addition, at least 5 mm.
Reinforced concrete columns are one of the most popular types of reinforced concrete products. They are vertically located building construction and are used as load-bearing elements of the frame: beams, crossbars, purlins, etc.
These products are designed to last forever high load in compression, they are also capable of bending, withstanding high wind loads. Our company produces reinforced concrete columns of any size in compliance with high quality standards.
Features and Key Specifications
In production they use either standard sizes, if the building is being erected according to standard project, or custom sizes in accordance with the drawings. Most often, these structural elements are manufactured to implement a specific individual project, in this case they correspond to all the personal wishes of the customer and the provided working documentation.
The cost of a reinforced concrete column is determined by several key factors:
- The class of concrete used in terms of strength, frost resistance and water resistance. Reinforced concrete columns of industrial buildings are subject to special strength requirements; accordingly, they will cost more.
- Reinforced concrete column size. The length can be from 5.7 to 17 meters, as a rule, the height is equal to the height of two floors of the building.
- Type of reinforcement cage, presence of embedded parts. Products for industrial buildings are equipped with high-strength reinforcement to increase resistance to compressive and bending loads. For them, prestressed or unstressed reinforcement is used.
- Availability of standard metal equipment. Also, the final cost depends on the time allotted for the production of reinforced concrete products.
Key characteristics of reinforced concrete columns – load bearing capacity. The lower it is located in the building structure, the higher it should be load-bearing characteristics, the highest requirements are placed on products installed in technical underground and on the lower floors of the building.
Types and materials for manufacturing
Reinforced concrete columns of one-story industrial and residential buildings are made from heavy grades of concrete M300-M600. Steel reinforcement provides the product with durability and high resistance to all destructive influences. The cross-section can be round, square or rectangular, it depends on the loads and the features of the structure.
For multi-storey residential buildings products with cantilever projections are used, used as a support for floor beams and become one of the main elements of the frame, since they have to withstand the main load.
Columns of the outermost and middle rows are also distinguished depending on their location in frame system building. Their connection with other frame elements is carried out by welding embedded elements, followed by concreting the joints. To install reinforced concrete columns of industrial buildings, special column foundations of glass or monolithic type are used.
Our company offers to place an order for any number of reinforced concrete columns,
Reinforced concrete and steel columns are used to construct the frames of one-story industrial buildings.
Reinforced concrete columns of one-story industrial buildings (Fig. 26) can be with or without consoles (if there are no overhead cranes). Based on their location in plan, they are divided into columns of middle and outer rows.
Depending on the The cross-section of the columns is rectangular, T-profile and two-branch. The cross-sectional dimensions depend on the acting loads. The following standardized dimensions of column sections are used: 400x400,
Rice. 25. Foundations of one-story industrial buildings a) types of foundation beams; b), c) details of the foundations of the outermost row of columns; 1- sand; 2 - crushed stone preparation; 3 - Asphalt or concrete covering(blind area); 4 - waterproofing; 5 - column; 6 - slag or coarse sand; 7 - reinforced concrete columns; 8 - foundation beam.
Rice. 26. Main types of reinforced concrete columns of one-story industrial buildings. A) rectangular section for a building without overhead cranes at a step of 6 m; b) the same, with a step of 12 m; c) two-leg for buildings without overhead cranes; d) rectangular cross-section for cranes with overhead cranes; e) the same, I-section; f) two-leg for buildings with overhead cranes; and) general form columns; 1 - embedded part for fastening the supporting structure of the coating; 2,3 - the same, crane beam; 4 - the same, wall panels.
Rice. 27. Main types of steel columns
a) constant cross-section, b), d) variable cross-section, e) separate
600x600, 400x800, 500x500, 500x600, 500x800 mm - for rectangular; 400x600 and 800x800 mm - for T-bars and 400x1000, 500x1000, 500x1300, 500x1400, 500x500, 600x1400, 600x1900 and 600x2400 mm - for two-branch ones. Columns can be made of several parts, which are assembled at the construction site.
Columns with consoles consist of over-crane and sub-crane branches. The cross-section of crane branches is most often square or rectangular: 400x400 or 500x500mm. For the manufacture of columns, concrete of classes B15, B40 and reinforcement of various classes are used.
The length of the columns is taken taking into account the height of the workshop and the depth of their embedding in the foundation, which can be: for rectangular columns without overhead cranes - 750 mm , for rectangular and I-section columns with overhead cranes - 850mm; for two-branch columns - 900-1200 mm.
The columns are provided with embedded parts (Fig. 2b,g):
1 - for fastening load-bearing structures coatings ( steel sheet, welded to special fittings);
2 - for securing crane beams from tipping over under the influence of braking forces;
3 - for fastening crane beams against displacement (steel sheet with four M16 bolts);
4 - for fastening wall panels (63x5, welded to the frame reinforcement before concreting the columns).
In addition to the main columns Half-timbered columns are used to install half-timbered structures. They are installed along the building with a pitch of outer columns of 12 m and a wall panel size of 6 m, as well as at the ends of buildings.
Steel columns of one-story buildings can have a cross-section that is constant in height or variable. In turn, columns with variable cross-sections can have a crane part with a solid or through section (Fig. 27). Through columns are divided into columns with branches connected by ties, and separate columns, which consist of independently operating tent and crane branches. Columns of constant cross-section are used when using cranes with a lifting capacity of up to 20 tons and a building height of up to 9.6 m.
In cases where the columns mainly work on central compression, columns of solid section are used. For the manufacture of solid columns, wide-flange rolled or welded I-beams are used, and for through columns I-beams, channels and bushings can also be used.
Separate columns are installed in buildings with heavy overhead cranes (125 tons or more). At the bottom of the columns, steel bases (shoes) are provided for connection with the foundations. The bases are secured to the foundations with anchor bolts, which are placed into the foundation during their manufacture. The lower supporting part of the column together with the base is covered with a layer of concrete