Calculator section of overlapping beam. The device of wooden beams of overlaps and their size. How to choose a cross section and a step between beams

Calculator section of overlapping beam. The device of wooden beams of overlaps and their size. How to choose a cross section and a step between beams
Calculator section of overlapping beam. The device of wooden beams of overlaps and their size. How to choose a cross section and a step between beams
09.07.2018

In any building there are overlaps. In their own homes, when creating a reference part, wooden beams that have a number of consumer properties are used:

  • market availability;
  • ease of processing;
  • the price is significantly lower than on steel or concrete structures;
  • high speed and ease of installation.

But, like any building material, wooden beams have certain strength characteristics based on which the strength calculation is calculated, the necessary sizes of power products are determined.

All calculations are made in accordance with the Eurocode. Compatibility with all well-known products on the market - direct import and export to the most popular drawing and notes. Dynamics of documents and graphs - the change in any function from the computing model is automatically reflected in text and graphic materials. Drawings and explanatory notes on excellent quality and export opportunities in text or graphic editor. Flexibility - take only those programs that you need. . In the following lines, we will look at the steel wooden composite structures and their use in construction.

Main types of beams

With domestic construction, several types of installation of reference elements are used:

  1. Simple beam, - It is a crossbar having two reference points at its ends. The distance between the supports is called spit. Accordingly, if there are multiple fastening points, there are two-, three-, and more spanted non-erect beams. In the design of the private house in this capacity there are intermediate wall partitions.
  2. Console, - The bar is rigidly fastened with one end in the wall or has one free end, with a length of more than double transverse size. The presence of two free hanging parts suggests that there is a double-circuit design. In practice, these are horizontal beams included in the roof and forming a canopy.
  3. Shipped product- Both endings are rigidly mounted in the wall. Such a scheme is found in the construction of the above-mentioned partitions and walls, while the beam is obtained mounted in a vertical design.

The advantages and problems of this type of construction are numerous. Benefits: increased gap strength, higher anti-sessimical safety and efficiency. Challenges arise due to differences in the properties of materials. Three types of tests and studies were carried out in three different ways to combine materials.

The first study concerns the anti-seeysmic support of multi-storey buildings from strained wood. The study was conducted at the University of Canterbury in New Zealand and aimed at developing a new type of composite construction system and connections for high-rise wooden wooden panels From natural veneer in seismic areas. It is believed that the new type of relationship will contribute to an increase in the durability of wooden buildings and will allow them to be in operation after earthquakes by reducing the number of victims, as well as the cost of repair and termination of various companies.

Horizontal overlap load

To calculate the strength, you need to know the loads arising during the operating system. The most significant values \u200b\u200barise on the first floor of a residential building. Smaller values \u200b\u200bare obtained for mansard structures and attic rooms. Voltages in the beam occur:

In addition to this study in a simplified version of the combined steel structure used on the three mentorio bridges, a table in a special format based on complex theory was developed for calculating strength and deformation. General characteristics Combined structures include the design and architectural advantages of various materials that can work independently or together, but in any case, their work is improving.

Canada uses various types of composite structures. In Quebec and Ontario, hundreds of composite steel bridges were built, in which steel is used as the main structural material in the form of steel main beams, and the tree is used for small elements, such as wooden beams. These applications are common and in buildings where they began to participate as a support frame, and the tree is used for flat elements.

The static load determines the two main types of voltage, - deflection along the entire length and bending in the place of support.

Although these two material are used in many places in Canada, their initial use in one design is located on the west coast of the country. Often the result is a combination of structures in which steel and wood jointly absorb vertical and horizontal loads.

The combination of wood and steel is becoming increasingly popular in many other countries of the world, such as USA, New Zealand, England. Over the past decade, a serious study was carried out by combined steel and wooden structures. However, the available information and details are not systematized and difficult to access the builders. This necessitates a more detailed study of compound wooden and steel structures to determine various combinations, advantages, difficulties and problems associated with their collaboration.

  1. Deflection - It turns out from the weight of the above-being elements. The maximum deviation arrow is obtained at the point of location of the object with the largest mass and (or) in the middle between the supports.
  2. Bend or Frame- This is the destruction of the crossbar at the dressing point. It occurs from the vertical load, and the beam itself, which perceives this tension acts as a lever. From a certain amount of effort begins a critical bending, leading to the destruction of the transverse support.

To reduce the effect on the strength of a wooden transverse product from internal structures, they are trying to be placed in the locations of the lower supports. Household appliances and furniture, if possible, it is advisable to place along the walls or near unloading structures.

Methods for combining wood and steel into a single structural structure of essentially three, and they can be summed as follows: Structure, system and material. The structure is the so-called "structure" is the main type of composite design, in which separate structural elements from different materials are used. Many examples of such combinations can be brought. One of the most common species is roofing farms. For example, it is possible to mention the structure of the roof farm in the Soutridge School, where compounds are simplified due to the combination of steel tensile elements and wood, depressed into an elegant indoor farm.

There are quite many types of wooden beams, but most accessible to the wide mass of the population are products of a rectangular or oval section. In the latter case, the beam is a rounded log, cropped from two opposite sides.

How to calculate the load on the ceiling beam

The total load on the elements of the overlap folds from its own weight of the structure, weight from internal construction productsLocated on beams, as well as the masses of people, furniture, household appliances and other economic utensils.

Advantages of wooden 2-way beams

Frames are another type of combined structure. The system system represents another combination method when steel and tree are assembled into the overall structural system. One example of this type of combination is new combined wooden connections developed by researchers at the University of Canterbury University in New Zealand. Connected systems of this type in principle are similar to reinforced concrete structures, tense after concreting. Compounds connect ready-made wooden elements using separate tension steel connections.

The total calculation, taking into account all the technical nuances, is quite complicated and is performed by specialists when designing a residential building. For citizens, elevating housing on the principle of "self-installation", more convenient simplified scheme into which the SNiP requirements are laid, decorating conditions I. specifications Wooden materials:

The design also has longitudinal steel reinforcement rods, which improve the seismic resistance of the connected system. Material This type of combination occurs when steel and wood simultaneously form a structural element similar to other types of composite structures in which two different materials Connected to collaborate in one element. This method is mainly used for the construction of bridges. Examples include bridges in Ontario, where the upper structure consists of pre-stressful flat wooden elements and steel beams using transverse bulkheads.

  • the length of the support part of the beam in contact with the foundation or wall should not be less than 12 cm;
  • the recommended ratio of the sides of the rectangle is 5/7, - the width is less than the height;
  • permissible deflection for the attic room is no more than 1/200, inter-storey floors - 1/350.

Snip 2.01.07-85 operational load on an attic design with a light insulation from mineral wool will be:

Another example is the Boku Bridge in Japan. The object consists of orthotropic steel road plateconnected to a bilateral wooden beam with a rectangular cross section. The strength of the beams increases by two vertical steel plates with a variable width. Slab is connected to beams with steel plates, which also work on the shift.

Overlapping options for different premises

The combination of materials is also used in the construction of residential buildings, but not as widespread. Typically, two wooden beams are combined with a metal plate between them and a bolted compound. Such a combination occurs during the construction of light frame buildings in North America. Such rays are absorbed large loads In large holes than a completely wooden beam of the same section. In Vancouver, to stop the Rupert station on Millennium-Line, this type of ray was used. The design of the stop consists of curved wooden beams connected by steel panels, steel round columns and steel wooden racks that form a three-frame frame.

G \u003d q + gn * k, where:

  • k is the safety reserve coefficient, usually for the buildings of small floors take the value of 1.3;
  • GN is a standard for a similar attic equal to 70 kg / m²; With intensive use of the attic space, the value will be at least 150 kg / m²;
  • Q is the load from the very attic overlap, equal to 50 kg / m².

Example of calculation

Given:

The roof consists of a light steel panel supported by glued wooden tables. The advantages of steel wooden structures. Although steel and wood are two very different material, combining them into the overall design can bring a number of advantages, given the properties and quality of each of them to overcome their disadvantages. A deep understanding and study of the properties of these materials is important for the design of such components. Engineers and architects must take into account the strength of each material and know, under what conditions each of them works best.

  • an attic in a residential building used for storing various economic inventory;
  • for insulation, clamzit with a light concrete tie is applied.

The overall load will be g \u003d 50 kg / m² + 150 kg / m² * 1,3 \u003d 245 kg / m².

Based on the practice, the middle efforts on the attic floor do not exceed the values \u200b\u200bof 300-350 kg / m².

For inter-storey overlaps, the values \u200b\u200bare in the range of 400-450 kg / m², and more important should be taken when calculating the first floor.

While the steel works best at voltage, the tree reacts better to compression. Therefore, in the construction of a composite steel structure, the tree must be provided in the pressed part, and the steel on the side of the stretch. The desire of architects is more rude, the so-called "rustic" effect on the type of roof design. The same should be seen to visitors in the lobby of the building, where exhibits are exhibited related to the history of the city. The farm structure is designed to support the roof.

In this carrier design, the steel part is on the tension side, and on the press side - glued bar. The combination of steel and wood improves the stability of structures to earthquakes. The tree has a high strength and weight ratio of elements, which makes wooden structures lighter than other building materials. This is a small weight that is beneficial for seismic events. Given the fact that the seismic force is proportional to the mass of the design, it can be expected that light wooden structures that are properly designed and built will be better working with earthquakes.

Council.When performing overlaps it is advisable to take the values \u200b\u200bof loads exceeding the calculated by 30-50%. It will increase the reliability of the design as a whole and will increase the overall life.

How to calculate the required number of beams

On the other hand, steel gives the plasticity of a wooden structure. Plasticity is the ability of the structure to develop plastic deformations and distract seismic energy without destroying it. Therefore, it is desirable that the building has similar properties, given the sudden nature of seismic events, because they will allow you to disperse seismic energy. They are covered with steel to better transmit seismic forces. The tree is an ecological construction product due to reduction of carbon dioxide emissions.

Section and pitch beams of wooden overlap

In this epoch global warming Strategies of sustainable development are not simply necessary, but increasingly imposed by the majority of governments. A tree, as the most stable, natural and renewable building material, needs widespread in construction industry. However, products such as glued wooden elements and treated wooden components are considered a product of the construction industry due to the production process. Although gluing and lamination increase strength and reduce wood moisture, they also make material suitable for recycling, like many other products made of wood.

The number of transverse support is determined by the loads per capita and the maximum deflection of the roughing coating, made, for example, from the board or plywood. Their hardness affects its own thickness of the product and the step between the points of the support, that is, the distance from the adjacent beams.

For premises with low operation (attic), it is allowed to use a board with a thickness of at least 25 mm, with a step between the supports of 0.6-0.75 meters. The inter-storey overlap of the residential zone is advisable to carry out a germ with a size of at least 40 mm and the distance along the nearest attachment points not more than 1 meter.

Thus, up to 30% of the loss of wood are formed, and some of the positive sides of the tree are lost as an environmental building material, given that it is a renewable resource. On the other hand, steel can be recycled largely, therefore, the combination of wood and steel gives a positive result from the point of view of ecology and sustainable construction.

Selection of the calculation scheme

In Canada and in most other countries of the world construction standards impose restrictions on the height and area of \u200b\u200bwooden structures from the point of view of fire protection, but there are no restrictions on the use of wood with non-combustible material, such as steel. Although wood is a flammable material, buildings built from solid wooden structural elements, have excellent fire-resistant properties.

Example of calculation

An attic space. The length between the walls is 5 meters. Weak operational load, - storage of all utensils. The flooring is carried out from a cut dry boards of coniferous rocks with a thickness of 25 mm. Taking the maximum step of 0.75 meters, the number of reference points should be:

5 m / 0.75 m \u003d 6.67 pcs., Sounding to an integer in a large side - 7 beams.

Then the refined step is:

5 m / 7 pcs \u003d 0.715 m.

Inter-storey overlap. Length between the walls of 5 meters. First floor with maximum load. The draft floor is performed from the product with a size of 40 mm. Step by supports are taken in 1 meter.

The number of fastening points is: 5 m / 1 m \u003d 5 pcs.

Council. Despite the low load per attic space, it is advisable to apply the requirements related to inter-storey overlaps, in the future there may be a probability of restructuring in the residential attorney.

How to calculate the desired section of the traditional wooden beam overlap

The strength characteristics of the support element are determined by geometrical parameters - long and cross section. Length, as a rule, is given from the internal dimensions of the inter-space and laid at the design stage of the building. The second parameter is a cross section, one can change depending on the intended loads during the construction process.

Example of calculation

To avoid enough surrounding mathematical calculations, give the recommended data that are reduced to the table. With the existing size of the span and step, you can determine the approximate section of the bar or the log diameter. The calculation was carried out on the basis of an averaged load of 400 kg / m²

Table 1

Song section of a rectangular timber:

table 2

The diameter of the rounded log:

Note:The tables present the minimum permissible dimensions. When designing its own building, it is necessary to take those sizes of wooden products that are present at the local construction market of the region, and the values \u200b\u200bare required to round up to the biggest.

Council. In the absence of a necessary bar, it can be replaced by boards, fastened with each other by joinery and self-tapping screws. Another reinforcement option is to increase the cross section of the bar, adding the boards of a certain thickness to its side sides.

Council. Extend the service life and reduce the flammability indicator will help with special fire and bioprotective equipment. In addition, such an operation contributes to a slight increase in the strength of wooden products.

Council. Those who still want to conduct mathematical surveys, on the calculations of wooden beams, for overlappings, it is advisable to look into the Internet with this question, "there is a sufficient number of sites on which electronic calculators are posted to determine the parameters of elements of power structures.

If in a private house on the inner structure, a ceiling device is planned, consisting of wooden beams, an important component preparatory stage The calculation of the exact dimensions, the best cross section of the rails and the step that should be retreated between them. It is necessary to calculate the size and number of rails, first of all, to save money, as well as to avoid shortage of building materials.

On the Internet today is offered a lot of online calculators, which allow you to make calculation as simple as possible and fast. Primary calculus involves determining the variety of used beams:

  • beams are suitable;
  • glued from the boards;
  • glued from veneer;
  • part of a cut log.

What measurements need

Wooden overlap beams, or rather exact quantity, is determined based on such data that is measured by a construction tape measure:

  • the sizes of the flight to which the rail will be fixed;
  • fixing options for wall structures, namely depth, estimated for fasteners;
  • estimation of the load acting directly during operation;
  • step and section are defined more often by special tables.

Wooden beams overlap and their length

The length of the ceiling deck depends on the size of the span on which they unfold construction worksplus it is desirable to take into account a small margin designed to put wooden beams into the wall. The length can be measured by itself, but the depth dimensions depend on the material used.

For example, if the walls are made of brick or a block system was applied, the wooden beams of overlapping go into the so-called nests, the depth varies in the range of 100-150 mm. Wooden structures should be equipped with a depth of 70 mm. The estimated use of metal fasteners, all sorts of clamps, corners determines the size of the regions equal to the span. There is a desire to build a sink roof, wooden beams of overlapping are outlined outside the house by 30-50 cm.

The most optimal sizes of the span, overlapping beams fluctuate in the range of 2.5-4 m. Experts are not recommended to exceed the length of the rails by more than 6 m, otherwise it is better to purchase a glued bar or use intermediate walls, columns.

Load calculation scheme at overlap

The load that acts on the overlap of wooden plates consists of several types of load:

  1. Own overlaid parts.
  2. Permanent or, on the contrary, temporary load, for example, if furniture, household appliances are installed on the upper floor. equipment.

The attic overlap that does not hold things, trash, and only takes into account the mass of the light insulation by type of mineral wool or foam and its own weight, is taken in the amount of 50 kg / sq. m. Based on this, the overlap operation load is calculated:

70 × 1,3 \u003d 90 kg / kV. M, 70 is the only adopted value of the load for the attic, and 1.3 - stock indicator.

Calculate the overall load:

(50 + 90) × 1,3 + 50 \u003d 232 kg / sq. m, round up to 240 kg / kV. m.

For the attic ceiling, where the attic is equipped, the weight of the floor design, partitions and furniture should be added. Then the load rises to a value of 300-350 square meters. m. Adjust the weight of several residents and visitors to the building and we get a load of 350-400 kg / sq. m.

Step-by-step guide for the calculation of wooden regques

When installed possible load On the wooden beams of overlapping, it's time to proceed to calculate the section of parts and the distance between them when fixing. For example, take the load of 300 square meters. m and span at 6 m. Then the section of the beam involves the use of the formula:

Size dimensions \u003d (20 × 22N) / (B \u003d 25). This formula is created by leading engineers and designers. So, we get: (20 × 22) / 25 \u003d 17.6 cm - the perfect dimensions of wooden beam overlap.

As for height, it is worth exploring the proportionality of the indicator of the material thickness that is selected as a reliable insulation. There should be at least 30 cm between the slats, but not more than 1.2 m. Focus on the dimensions of the insulation blade blocks, locking in an inter-worker space, or on the ceiling plane binder panel.

The bar fixation step must correspond to the step of the racks of the frame base, according to professionals, this simple technique will make it possible to achieve better stiffness of the installation, reliability and strength of the structure.

If you are still not sure own powerAfter calculating the dimensions of the parts necessary to arrange the overlap, examine the reference information of technical textbooks, which is presented for convenience in a tabular version.