Installation of maximum support for reinforced concrete run. Installation work during the construction of brick buildings. Coverings by purlins

Concreting purlins

Concreting of purlins, beams and slabs should begin 1...2 hours after concreting the columns and the initial settlement of concrete in them.

Purlins and beams with a height of more than 50 cm are concreted in layers of 30...40 cm, with each layer individually compacted with deep vibrators. Densely reinforced purlins and beams are compacted using vibrators with special attachments. Last layer concrete mixture not brought to the bottom plane of the slab by 3...4 cm.

The floor slabs are concreted over the entire width at once and compacted with surface vibrators.

Arches and vaults with a span of less than 15 m are concreted continuously simultaneously on both sides from the heel to the castle. Vaults with a span of more than 15 m are concreted in separate sections. In this case, the concrete mixture is laid in strips simultaneously in three areas in the castle and at the heels. After this, individual strips are concreted, between which shrinkage gaps of 20...30 cm are left, which are sealed with a low-flow concrete mixture 5...7 days after concreting the strips. Tightening of vaults and arches is tightened before concreting.

On steep sections of arches or vaults, in order to prevent the concrete mixture from slipping during vibration, concreting is carried out in double-sided formwork, the outer panels of which are built up during the concreting process.

The start of concreting must be preceded by a thorough inspection (with the drawing up of a report) geometric dimensions, stability and strength of the formwork.

Technology of construction of residential and civil buildings from monolithic reinforced concrete. Along with fully prefabricated factory housing construction, the construction of buildings made of monolithic reinforced concrete is gaining some momentum in the country. This type of construction turns out to be advisable:

1. if it is necessary to solve urban planning problems through the construction of atypical buildings of a tower composition;
2. during construction in areas of high seismicity or on the territory of mine workings, where increased requirements to the spatial rigidity of buildings;
3. when constructing buildings in areas significantly removed from house-building enterprises.

Strength building structures help to provide reinforced concrete products. Their shapes and sizes are varied. Some produce directly on construction site, others are prepared in production. No construction is complete without reinforced concrete purlins.

Definition

The appearance and structure of the purlin are almost no different from a reinforced concrete pillar. Outwardly they look like frozen concrete mortar With metal frame inside. What is the difference between the runs? Designs differ large mass, long and reinforced with strength. The production of structures is not on stream; their production is associated with the need for the element to withstand a certain load.

Purpose

Reinforced concrete purlins are used in construction to solve important task. For example, not a single opening can be made without using a purlin. Only after its installation are the floor slabs attached. And reinforced products made under the influence heat treatment, withstand heavy loads. Used in public construction, industrial buildings with brick and reinforced concrete walls. Most often they are used in the construction of openings, supports on which floor slabs are attached.

Reinforced concrete purlins are prepared exclusively industrially, according to state building standards. For their production, only heavy concrete is used, most often M200 and M300, with the use of reinforcement for reinforcement. Use of structures in favorable conditions increases the service life of buildings.

Kinds

Reinforced concrete purlins are divided into types, which are formed according to the shape of the product and the grade of concrete. The runs are assigned following types

T-section

Channels and I-beams are used in production. Subdivided this type into two types:

• The first group includes products with metal located perpendicular to the rib of the purlin. They are suitable for the construction of buildings that have a roof slope of approximately 25%. 1PR rod frame, 2PR pre-stressed, 3PR is used when the roof slope is no more than 5% - varieties of the first group.
• The second group includes products that can withstand a roof slope of 25%. It includes products 4PR stressed and 5PR artificially created tension.

These designs can be used for unheated rooms. Used in temperature conditions from - 40 to 50 degrees and exposure to gas. Characteristic feature is the ability to use products in the construction of structures in hazardous, seismically active zones.

The difference is the presence of special holes, through which the gripping devices are inserted, making it easier to lift and install the elements. Elements with T-section suitable for building construction:

• unheated with a roof made of cement and asbestos fibers;
• heated with lightweight ceilings;
• heated with cement roof.

Rectangular section

This type of purlin has an I-beam division. The rectangular cross-section of the purlins can be solid or lattice. The lattice type is lighter, the spacing of products is 6 meters, so it is used in construction much more often. To produce a continuous type, bent channels are used. Products with a rectangular cross-section have thin walls, but excellent height. The strength of the products is ensured by specially created fastening bends.

Marking

The manufacture of building structures is approached in compliance with state standards and technology. You can get maximum information about products by studying the product series. An inexperienced builder will not be able to get full information on labeling without knowledge. It is worth focusing on the transcript data.

For ease of use, a special classification in letters and numbers is used. They encrypt information about length, height, width, and support load. The first letters encrypt information about the series of runs:

• P - one-piece product.
• PR - the presence of a side located parallel or at an angle to the axis of the element.
• PRG - rectangular section.

The second group of signs contains information about the load and type of reinforcement. The third signs indicate the specific purpose of the material, including the features of the use of concrete composition.

For example: PRG 28-1-3-4t. PRG - rectangular section. The following series of numbers indicates the dimensions of the structure: 2800 mm long, 100 mm wide, 300 mm high. The 4t indicator indicates the ability to withstand a load of 4 tons per meter.

A purlin in roof construction is a horizontally placed beam between the supporting structure and the roof sheathing. His key functions– load transfer from roofing, its uniform distribution in the rafter system, as well as ensuring the rigidity of the sheathing.

Purlins are made of wood, steel and reinforced concrete and are used in the construction of roofs of industrial buildings and private houses. They are also installed as bases for floor slabs and to strengthen openings.

Purlin in the rafter system

Roofing and construction beams

Before starting construction, study the types of beams to get an idea of ​​how the roof works. Each beam has its own purpose and occupies a certain place in the floor system.

Roof bars are made of metal, solid wood or lamellas glued together. Bent-laminated beams are manufactured in accordance with GOST. They are easy to work with, are little affected by weather conditions and are used to increase the intervals between runs. The cross-section of the elements can be rectangular, T-shaped or I-beam. The I-beam shape (H) guarantees the rigidity of the beam and reduces the bending moment to almost zero.

Scheme of a broken roof with a purlin

Types of wooden construction beams V support system roofs:

• Mauerlat - a square beam laid on the walls to support the rafters;
• ridge - support beam at the top of the roof;
• rafter beam - forms the angle of the roof;
• tightening and crossbar - connect the rafters of opposite slopes;
• filly - extends the rafters, forming a roof overhang;
• strut - located at an angle to the vertical elements and supports the rafters;
• run.

Lathing scheme from wooden elements

The purlins are fixed on supports at a distance of 4-5 meters from the ridge, and expansion supports are placed between them. If it is necessary to lengthen the rafters, the joint is placed above the purlin.

Structure and types of metal beams for roofs:

• bottom belt
• upper belt
• lattice.

The lattice is assembled from racks and braces and attached to the belts on both sides using shaped elements.

Types of purlins for roofing

Purlin supports are classified by location in the roof slab system, as well as by shape and material.

Types according to the place of application in the rafter system

There are three types of purlin supports - side, ridge and mauerlat.

Ridge run- this is the highest beam of the roof, it is mounted in the upper parts of the gable walls, and the edges are wrapped waterproof material. If necessary, the structure is reinforced with racks. The rafters rest on the ridge with their upper end.

Ridge fixed in the gables of the walls

Mauerlat or matitsa - thick timber with a cross section of 150x150 mm, which is laid on load-bearing walls parallel to the ridge in order to equally distribute the load from the roof. The Mauerlat boards are called the roof foundation and are firmly secured with anchor bolts to the walls, having previously laid down waterproofing material. In brick buildings, the matrix is ​​installed in a pre-prepared armored belt made of reinforced concrete on reinforcement.

Mauerlat laid on top of a concrete wall waterproofing material

The side purlin connects the rafters in the middle - with its help they strengthen the roof, reducing the bending load of the rafters. To transfer the load to the floor, install under the side girders vertical racks.

Classification of beams by material

As mentioned above, according to the material, purlin supports are classified into reinforced concrete, metal and wood. Metal purlins are manufactured industrially and can be uniform or lattice. The first ones are made from channels and I-beams - they are easy to manufacture and install, and cost 10% less than lattice ones. Disadvantage of grid purlins – high price And a large number of complex nodal elements. The advantage is light weight.

Runs can be:

• whole;
• compound.

Composite beams are used when it is necessary to cover a roof large area to avoid distortion from bending loads.

Categories of wooden supports by design

Structurally, purlins are classified into:

• continuous;
• split;
• with struts;
• cantilever-beam;
• with support beams.

Split ones are rows of wooden supports fixed to the roof slopes and supported by supporting structures - racks. Often secured with struts and struts.

Scheme of cantilever-beam and continuous purlins

Cantilever-beams are enfilade rows of boards less than 6.5 m long, the joints of which are located outside the support beams. In this case, two consoles are formed in the middle gaps, and one in the extreme gaps. Cantilever beams are used in the construction of pitched roofs load-bearing structures up to 4-5 m.

Continuous purlins are suitable for roofs with a slope of up to 15° and a covering made of lightweight materials - roofing felt or flexible tiles. With a greater slope, thin beams cannot withstand bending loads and break.

To strengthen the structure in construction, struts and beams are used:

• A support beam is a small block mounted on support post. Relies on her load-bearing beam battens.
• A strut is an inclined beam that supports horizontal beams and works in compression.

The struts contribute to the uniform redistribution of loads from the coating to the supporting elements.

Grouping of reinforced concrete purlins by profile

Purlins made of reinforced concrete are marked according to their cross-sectional shape and load. The cross-sections of the purlins are:

• T-bars;
• rectangular.

Rectangular reinforced concrete block

T-type beams are divided into two more groups:

• beams with metal perpendicularly attached to the ribs of the purlin - installed on roofs with a slope of up to 25%;
• supports that can withstand a roof slope of more than 25%.

T-bar supports are used in the construction of roofs unheated premises large areas, as well as in seismically active regions. They endure subzero temperatures up to -50°C. Key Feature T-bar reinforced concrete supports– presence of holes for hooks and other gripping devices, ensuring ease of installation.

Supports rectangular section– tall and thin-walled, durable due to bends. They are classified into solid and lattice.

Gradation of metal components by profile

Solid metal purlins are beams bent profile several types:

• C-shaped;
• I-beam;
• Z-shaped;
• T-bar;
• channel

The T-profile in cross-section resembles the letter T, the I-beam - H, and the channel - the letter P.

Types of metal beams with lattice profile:

• rod-truss with a lower chord and a round steel grille;
• three-panel.

The three-panel girder is accepted as standard due to the smaller number of components and ease of manufacture. The upper chord of the beam is made of double channels, and the lattice is made of curved single channels.

Labeling of industrial products

Purlins in construction are critical structures; they are manufactured in strict accordance with GOST and marked. To select beams that correspond to the purpose of the roof, you need to be guided by the product labeling.

Reinforced concrete blocks for roofing

Reinforced concrete purlins are marked with letters and numbers, including information about the dimensions and support load of the products. The letters indicate the series and design features purlin:

• PR – T-shaped beam with a side;
• P – one-piece purlin;
• PRG – support of rectangular section.

The numbers indicate the length, width and height of the purlin, and the latter indicates the load that it can withstand, in tons. The marking may also include values ​​about the reinforcement of the product. Purlins can be unstressed, reinforced with a steel frame or prestressed, with additional longitudinal reinforcement bars to increase bearing capacity.

Product dimensions are taken into account when marking

Also in production reinforced concrete structures use markings like:

• 1PR – for flat roofs with reinforcement without reinforcement;
• 2PR – for flat roofs with reinforced reinforcement;
• 3PR – for structures with a slope of up to 5%;
• 4PR – for roofs with a slope of up to 25%;
• 5PR – with a diagonal shelf for steep roofs.

An example of marking a reinforced concrete purlin with decoding: PRG 48-2-5-4tAIII-1. This is a rectangular girder with dimensions 4800x200x500 mm and permissible load 4 tons. It is pre-stressed and reinforced with additional reinforcement. Suitable for the construction of heated and unheated critical structures in areas with poor weather conditions and seismically active zones.

Metal roof elements

Metal beams marked by profile, design, material and dimensions.

Classification and marking of I-beams:

• Ш – with a wide shelf;
• K – columnar;
• B – ordinary.

The number before the letter indicates the conditional height of the beam in mm, the remaining dimensions are selected in accordance with GOST. For example, for support 30B1 the height is 296 mm, and the letter “B” denotes a normal beam. The dimensions of the beams are in the range of 10-100 mm.

Production of hot rolled purlins

Metal beams for purlins are made of steel by welding or hot rolling - for each manufacturing method, GOST is provided, which describes the marking of products.

Advantages and disadvantages of purlins depending on the material

When planning to build a roof, compare positive sides and the disadvantages of each material. For example, metal does not provide sufficient energy efficiency for a building, but it is durable. Wood is susceptible to rotting, but retains heat.

Metal beams in construction

List of pros and cons for metal purlins.

Advantages:

• withstand significant load;
• fireproof;
• durable;
• There is no waste during installation, thanks to high precision details.

Flaws:

• freeze when low temperatures;
• difficulties in transportation;
• heavy weight relative to the tree;
• expensive material.

Metal is susceptible to corrosion

List of positive and negative characteristics wooden beams.

Advantages:

• economical;
• easy to install;
• retain and transfer heat.

Flaws:

• annual treatment with antiseptics is required;
• there is a risk of roof fire.

Below are the pros and cons of reinforced concrete products.

Wooden rafter system

Advantages:

• increased fire safety;
• environmental friendliness;
• strength and durability;
• not subject to corrosion and rotting.

Flaws:

• heavy weight;
• the complexity of installing and securing elements.

In private housing construction rafter systems most often made from wood, and metal elements– purlins or crossbars, further strengthen the structure. Reinforced concrete blocks used in the construction of roofs of industrial buildings.

The reliability of the roof does not allow for savings, so be sure to consult with a specialist to clarify all the nuances and get advice specifically on your construction project.

Reinforced concrete purlins PRG are manufactured in accordance with series 1.225-2, intended for covering openings in walls public buildings and administrative buildings made of brick or wall blocks and designed for a design pressure of 4000 kgf/m, i.e. used in load-bearing walls with the possibility of supporting both PC floor slabs and the overlying masonry.

Made from heavy concrete grade M-250 for compression, and for 6-meter ones - M-350. Reinforcement is possible in 2 options: prestressed, reinforced with prestressed reinforcing bars of the AtV brand and spatial frames and unstressed, reinforced only with spatial steel frames. Most often they are produced unstressed, i.e. with conventional reinforcement

Since the load of the overlying wall is quite large, and the surface area on which the purlin presses is quite small, it is recommended to use base plates, which allow you to distribute the load over a larger surface.

The standard length of the product provided by the series can be 2.8; 3.2; 3.6; 4.2; 4.8; 5.4 and 6 meters. However, it is possible to produce reinforced concrete purlins and intermediate sizes upon request.

Marking

The marking consists of alphanumeric groups separated by a hyphen:

• The 1st group contains the designation of the PRG type - rectangular purlin and dimensions(length, width, height in dm.).
• Group 2 includes the design load without taking into account its own weight (in tons/m) and the class of reinforcement used.

For example, PRG 32.1.4-4AtV - a rectangular girder with a length of 3180 mm, a width of 120 mm, a height of 400 mm under a design load without taking into account its own weight of 39.2 kN/m (4 tn/m), reinforced with AtV steel, i.e. . pre-stressed.

Dimensions and support