TTK. Capital repairs of buildings

Strengthening piers and lintels

Walls and lintels are among the most loaded sections of the walls and therefore are often reinforced.

Traditionally, steel and reinforced concrete cages are used to reinforce the walls, although in some cases it is advisable to plaster over the grid or lay them with bricks.

With small vertical and inclined cracks, the piers are reinforced with reinforcing meshes made of wire with a diameter of 3-5 mm with a cell of 100x100 mm (Table 4.4, clause 1). The grids are welded to form closed loop. For a better fit of the mesh to the wall, pins (nails) 100-150 mm long are used, driven into the seams of the masonry. Shotcrete or a layer of plaster 15-20 mm thick is applied to the reinforced wall.

With large vertical cracks, the pier is reinforced with a steel clip (Table 4.4, clause 2), which is mounted on a pre-plastered and leveled surface of the pier. The holder is a construction of longitudinal corners 50x50 (45x45) mm and strips welded to them from a steel strip 50x5 mm with a pitch of 300-500 mm. In this case, the spacing of the bars should not exceed smallest size pier. To create a prestress in the cage and improve its joint work with the brickwork, the strips are sometimes heated to a temperature of 150-200 ° C before welding.

However, this method of clip prestressing is quite laborious and difficult to implement, and therefore is rarely used. More technologically advanced is prestressing, which is achieved using a mortar prepared on an intensifying (expanding) cement and injected into the gap between the corners and the brickwork.

The walls, which have a complex configuration and surface damage, are reinforced with a reinforced concrete clip (Table 4.4, p. 3). The clip is made of concrete class B15-B20 and reinforced with a spatial frame consisting of longitudinal and transverse rods. The thickness of the reinforced concrete cage and the cross-sectional area of ​​the longitudinal reinforcement are determined by calculation.

Table 44

Ways to strengthen (replace) the wall

No. p / p	amplification methods. Gain Sketch	Gain elements
pos. no.	Material, dimensions
	Plastering on the grid		Nails l=100-150 Wire mesh, class. Вр1 Ø=3…5 mm; cell 100x100 Cement-sand mortar M100; δ=15-20
	steel clip		Corner 50x50x5 Planks 50x5 with a step of 300-500
	Reinforced concrete clip		Longitudinal reinforcement Cl. AII, AIII Ø=6..12 Transverse reinforcement class. AI Ø=6…8 Concrete class. B15-B20 δ=40-60
	Wall replacement		Racks Boards δ=30-40 Boards δ=50-60 Wooden wedges New wall

In the project of strengthening piers of great length (when their length is two or more times greater than the thickness), it is necessary to provide for the setting of additional ties passed through the pier masonry.

In case of significant destruction of masonry, it is advisable replacement of the wall with a new one. Shift (replace) the partition after preliminary unloading. For this purpose, wooden posts are installed in the window openings adjacent to the wall, which are embroidered with boards to ensure rigidity and stability. The load from the jumpers to the racks is transmitted through wooden wedges, driven by surprise with the rack (Table 4.4, clause 4). After the installation of the wall, the gap between the new and old masonry is minted with a hard mortar.

It is important to note that the materials for laying a new wall and repairing a wall must have similar physical and mechanical characteristics. This makes it possible to exclude uneven deformations of the wall and possible overstressing of the wall.

Damage to lintels above door and window openings usually observed in old buildings with great physical wear and tear, and is characterized by the appearance of vertical cracks and the loss of individual masonry stones.

Jumpers reinforce steel corners (channels) or reinforced concrete beams installed in pre-arranged nests (Table 4.5). Reinforcement corners are combined when welding with horizontal plates, and channels - with plates or bolts. The load from the lintel, perceived by the steel elements, is transferred to the walls by means of a suspension made of strip steel or through steel beams of an angle or channel profile, embedded in holes punched in the wall.

An analysis of data on deformations of buildings and structures under the conditions under consideration showed that the choice of a method for strengthening load-bearing structures depends on the engineering and geological conditions (soil properties) and the degree of their study, the nature and magnitude of the applied load, the detail of the examination of existing foundations, the safety of existing structures, the method of production work and the type of equipment used.

Particularly dangerous deformations occur in old buildings built without taking into account the development of uneven settlements, which have received damage and have numerous defects that weaken bearing structures: cracks in the walls, shifts of ceilings and flights of stairs, distortions of openings, wall deviations from the vertical, etc.

Based on the features and nature of the junction, certain structural measures are taken to ensure operational suitability existing buildings: preventive design solutions; preventive measures necessary in the course of work; repair measures in the event of an emergency.

Strengthening of structures can be performed on a temporary and permanent basis. Temporary strengthening of structures is used in cases of long-term development of deformations in the event of emergency damage to buildings. As the deformation stabilizes, the temporary reinforcement is replaced by a permanent one.

Strengthening of structures, both preventive and restorative, is carried out by increasing the bearing capacity of the elements of the structure or by changing the structural scheme of buildings by increasing its spatial rigidity and strength.

To date, numerous recovery methods have been developed and tested in practice. operational qualities buildings. Some methods make it possible to strengthen over-foundation structures by fastening walls in brick houses, by installing overhead and stressed belts, unloading beams, brackets, couplers, etc. Other methods increase bearing capacity foundations, reconstruct or reinforce the foundation by arranging a solid foundation slab, expanding or deepening the foundation, driving piles of the Mega type, stuffed, bored, etc. under the walls of the building, pressing in existing piles with an increase in their length.

Before starting work on strengthening individual structures, it is necessary to unload them by installing temporary supports. However, mistakes are often made here: the load of the deformed structures lying above is concentratedly transferred to the deforming foundation and, thereby, its working conditions worsen. The load must be redistributed in such a way as to unload the fully or partially deforming foundation, i.e. transfer it to a reliable foundation, sometimes through specially made supports (platforms). Temporary supports must be constantly monitored and, if necessary, wedges should be knocked under them or additional unloading supports should be installed.

Deformed piers between window, door or other openings brick buildings reinforced by the device of metal or reinforced concrete corsets (clip). If temporary fastening of the masonry lying above is made, the piers can be reinforced by partial or complete re-laying.

The design of the metal corset consists of uprights angle steel with a width of shelves 100-120 mm, covering the corners of the wall, and welded to the posts at a certain interval of horizontal strips of steel with a thickness of 6-8 mm. Such a corset almost doubles the bearing capacity of the wall (Fig. 8.3). With inside buildings, parts of the metal frame are arranged with penetration into the body of the wall and subsequent plastering of the furrows. Reinforced concrete corset is used in cases where stress in the working section of the pier can cause destruction of the masonry. The posts of such a corset can also be located in vertical grooves punched in the masonry of the piers.

Rice. 8.3.

1 - brickwork; 2 - metal bar; 3 - corner

In cases where dangerous cracks appear in the building structures at the junction of the main walls to each other, the walls deviate from the vertical plane and their individual sections bulge, in order to prevent further development of deformations, overhead belts are arranged (Fig. 8.4). These belts are a system of paired vertical anchors from channels No. 12–14, united by horizontal strands of round steel with a diameter of 18–28 mm. Strands are best arranged at the level of reinforced concrete floors with their subsequent shelter under the floors. The tension of the strands is carried out manually using couplings with reverse threading. Strands are calculated according to the tensile force of the masonry. With outer side anchors and strands can be sunk into the shtraba, which is then plastered.

Rice. 8.4.

1 - overhead belt from the channel; 2 - metal cord

In winter, the possibility of frost on the metal parts of the overhead belts inside the buildings is not ruled out, therefore, heat-insulating pads must be installed on the outer part of the strands.

Kozlov's stressed belts are used in cases where cracks occur in the walls of buildings with a significant opening and a large length. Such belts give the building spatial rigidity, relieve tensile stresses in the masonry and transfer them to the metal (Fig. 8.5).

Rice. 8.5.

a- facade; b- plan of a part of the building; in- options for placing strands; 1 - reinforcing strand with a diameter of 22 - 32 mm; 2 - fine

The use of stressed belts has certain advantages over other methods, since they provide: alignment of uneven deformations of the building box; carrying out restoration work without disturbing the normal operation of the building; exclusion of the re-laying of significant sections of the walls; economical use of metal for the restoration of damaged walls and buildings.

Tension belts consist of metal rods with a diameter of 22-32 mm, covering the damaged building or its compartment at the level of interfloor and attic floors. The rods are usually tensioned by hand with threaded couplings. To install the belt rods, horizontal strokes are punched from the outside of the walls. The rods are attached to the supporting parts, which are vertical corners No. 10-15, installed at the corners or intersections of the walls. Belts must be closed. According to the methodology of the Academy of Public Utilities. K.D. Pamfilov, the length of the long side of the belt should not exceed 1.5 of the length of the short side. The long side is usually 15-18 m. The belt covering the deformed part of the building must be wound on the undamaged part for at least 1.5 lengths of the deformed section.

The cross section of the strands is selected according to the force, which depends on the design resistance of the masonry to chipping, the thickness of the wall and its length. The section of the rods that perceive the bending moment in the wall is assigned such that their strength is equal to the strength of the masonry that perceives the shear force:

N = 0,2Rlb ,

where N— force in the rod, kN; R- design resistance of masonry to chipping, kN / m 2; l— wall length, m; b- wall thickness, m.

Cracks in the walls of the building can be strengthened with braces installed at the level of each floor. The purpose of such brackets is to redistribute the load from the deformed sections of the walls to strong sections. This measure prevents further crack opening. The screed bracket (Fig. 8.6) consists of cutting a channel or a corner at least 2 m long, fastened to the wall with two anchor bolts with a diameter of 20-22 mm. The anchor bolt is located at a distance not closer than 1 m from the crack.

Rice. 8.6. Reinforcing masonry buildings with braces or relief beams (dimensions in cm)

a- facade; b- amplification fragment, 1 - bracket-screed; 2 - unloading beam from the channel at the level of the top of the foundation (at the level of the 1st or basement floor), 3 - pinch bolt 4 - plank anchor; 5 – concrete grade 100

Unlike braces that provide local reinforcement damaged area walls, unloading beams serve for the general strengthening of the building. Usually they are arranged from channels No. 22-27 and placed at the level of the top of the foundation or at the level of the window lintels of the first or basement floor (see Fig. 8.6).

Double-sided unloading beams are installed with a wall thickness of more than 64 cm and anchored with bolts with a diameter of 16-20 mm every 2-2.5 m.

Screeds-screeds and unloading beams are installed on a cement mortar in a groove with a depth of at least the width of the shelf. At the end of the fastening of the anchors, the shtrab is filled with concrete grade 100 with compaction. All metal parts braces and unloading belts must be coated with anti-corrosion compounds.

For large-panel buildings due to their design features other reinforcement solutions are needed. For such buildings, preventive measures are carried out by introducing horizontal floor reinforcement (Fig. 8.7); strengthening the fastening of floor slabs on the panels of internal and external walls (Fig. 8.8); the device of cantilever supports of floors (Fig. 8.8, in); reinforcement of vertical joints, etc.

Rice. 8.7.

a- anchors; b- strands; 1 - anchor; 2 — Wall panel; 3 - heavy; 4 - reinforcing cage; 5 - strands; 6 - plaster on the grid; 7 - metal corner

Rice. 8.8.

a- hanging ceilings; b- the use of wall panels with cantilever widening; in- installation of stiffeners; 1 - metal earring; 2 - beam; 3 - overlap; 4 - Wall panel; 5 - heavy; 6 - cracks, chips; 7 - console; 8 - plaster on the grid

Increasing the spatial rigidity of a structure by changing the structural scheme makes it possible to redistribute forces in structures, ensuring their more efficient operation. To do this, you can install additional designs in the form of racks, struts, portals, introduce connections, diaphragms, spacers, etc. (Fig. 8.9).

Rice. 8.9.

a- additional column; b- struts; in- portal; G- struts

These methods are primarily applicable to multi-storey buildings. industrial buildings frame type, are quite effective and allow unloading structures that have received damage. In all cases, reinforcing elements must be included in joint work with existing structures. For this purpose, reinforcing elements are crimped with jacks, wedged, gaps are filled with mortar on expanding cement, etc.

During the operation of stone structures, signs of their destruction may appear for various reasons - open cracks appear in the elements (see Fig. 5.27). Such structures can continue to be used after they are strengthened by enclosing masonry in a holder.

The need for reinforcement may also arise when operating conditions change, for example, when loads increase as a result of the reconstruction of buildings, the construction of superstructures, etc.

Clips, which should fit snugly against the brickwork, are made of steel, reinforced concrete, reinforced. Masonry, enclosed in a cage, works under conditions of limited transverse expansion (the cage prevents the expansion of the masonry), which increases its bearing capacity by 2-2.5 times. The inclusion of pillars and piers with cracks in the cage can completely restore their bearing capacity. The most efficient operation of the cage, which provides for the transfer of the load (the cage rests on the upper and lower structures), in this case, it not only restrains the transverse expansion of the masonry, but also perceives part of the load, unloading the reinforced element.

Steel clips are made by setting the corners of the pillars and piers of steel rolling corners on the solution. The corners are connected by strips made of strip steel, which are welded in increments of not more than 500 mm and not more than the smaller side of the section of the reinforced element. To protect the steel casing, it is covered with a layer of cement mortar 25-30 mm thick along a metal mesh, which ensures reliable adhesion of the mortar, or the casing is painted (Fig. 5.34, a).

The reinforced plaster clip is made of vertical rods and clamps and is plastered with a solution of M75, M100 with a thickness of 30-40 mm (Fig. 5.34, b). Similarly, it is possible to make a reinforced concrete clip, taking the thickness of the clip 40-120 mm.

Rice. 5.34. Reinforcement of the wall with clips: a) steel clip;

b) reinforced plaster clip; 1 - partition; 2 - corners;

3 - strips 35x5-60x12 mm; 4 - plaster; 5 - vertical rods 0 8-12 mm; 6 - clamps Ø 4-10 mm

Column Calculation Examples

Example 5.1. Using the data in Example 3.7, calculate the steel column for the store building. The column is made of a rolled I-beam with parallel flange edges. Load N= 566.48 kN (in fact, loads from the weight steel beams and the steel column is less than the loads taken according to example 3.7, in which the loads are determined from the weight of reinforced concrete beams and brick column, but to compare the results of calculations in examples 5.1, 5.2, 5.3, 5.4, the loads are assumed to be the same). Reliability coefficient for responsibility is accepted y„ = 0.95; load, taking into account the reliability factor for liability 566.48 0.95 = 538.16 kN. The column is actually made two stories high, but the estimated length is taken equal height one floor, since its fixing in the ceiling 1e / - 3.6 m is taken into account. Design scheme the column and its section are shown in fig. 5.35.

1. We determine the group of structures according to Table. 50* SNiP P-23-81*; the columns belong to the group of structures 3. We accept steel C245 according to GOST 27772-88 (when accepting steel, it should be taken into account whether this rolled product is made from this steel or not, since often a certain type of rolled product is made from limited types of steels (see Appendix 1, table 2).

2. We determine the design resistance of steel according to Table. 2.2, taking into account that the I-beam refers to shaped steel, and having previously specified its thickness / up to 20 mm, / ^ = 240 MPa = 24 kN / cm2.

3. When calculating stability, we take the coefficient of the working conditions y = 1 (Table 2.3). We set the flexibility of the column X-100, which corresponds to the buckling coefficient Ф ~ 0.542 (Table 5.3). Determine the required area:

4. Determine the required minimum radius of gyration (for a given flexibility X = 100): / = 4/A. = 360/100 = 3.6 cm.

5. According to the required area and radius of inertia, we select an I-beam according to the assortment of I-beams with parallel edges of the shelves. The I-beam 23Sh1 is the closest, which has the following characteristics: A = 46.08 cm2; /x = 9.62 cm; 4= 3.67 cm.

6. Check the selected section:

We determine the greatest actual flexibility (the greatest flexibility will be relatively y-axis, since the radius of gyration from

the same calculated lengths of the sections of the columns are different. The smallest section has a steel column, the largest section has a column made of unreinforced brickwork. The cross section of a wooden column is smaller than the cross section of columns made of reinforced concrete and masonry.

Tasks for independent work

Problem 5.1.

Select the section of the main steel column, made of a rolled I-beam: the load acting on the column is N - 300 kN; reliability factor for liability % = 0.95; steel C 235; coefficient of working conditions us= 1; estimated length of the column 1^=6 m.

Problem 5.2.

Determine the bearing capacity of a steel secondary column made of a rolled I-beam 20K2. The load acting on the column, 20 kN, is applied along the center of gravity of the section; steel C245; working condition coefficient y = 1; estimated length 1e/= 5.0 m.

Problem 5.3.

Check the strength of the centrally compressed brick pillar. The load acting on the column, N- 340 kN; N,= 250 kN. Reliability coefficient for liability yn = 0.95. Post section 510x640 mm; silicate brick M75; cement-lime mortar M50. Calculation scheme - hinged fastening of the column on the supports; column height H = 4.2 m.

Problem 5.4.

Select the cross section of a centrally compressed brick pillar Estimated length / 0 \u003d 2.8 m. Load N - 120 kN, N - 100 kN. Reliability coefficient for responsibility y„ = 0.95. Clay brick of plastic pressing M75; cement-lime mortar M75.

Task 5.5.

Check the strength of a centrally compressed brick column made with mesh reinforcement. The column is subjected to a load N- 380 kN. Reliability coefficient for liability yn - 0.95. The section of the column is 640x640 mm. Clay brick of plastic pressing Ml25; cement-lime mortar M50. The column is reinforced with meshes made of Vr-1 class rebar, 04 mm. Step of reinforcing bars in grids (cell size) с- 60 mm; mesh pitch 5= 154 mm.

Problem 5.6.

Pick up a section of a wooden rack from a bar; the rack is hinged at the ends, the length of the rack is / = 2.0 m. The load is applied along the center of gravity of the section, N- 15 kN. Hope factor

responsibility for liability yn = 0.9. Material: birch; grade 2. Temperature and humidity operating conditions B2 (outdoor operation in the normal zone, for such operating conditions, the TV coefficient = 0.85). When determining the design resistance of birch, the design resistance determined for pine (spruce) wood should be multiplied by the coefficient tp (Table 2.5), taking into account another type of wood, and the coefficient tb, taking into account operating conditions. The ultimate flexibility of the rack Xmax = 120.

Problem 5.7.

Check the bearing capacity of a wooden post made of logs. Material: spruce, grade 3; operating conditions A3 (coefficient tb = 0.9). The load acting on the post is applied along the center of gravity of the section, N- 150 kN. Reliability coefficient for responsibility y„ = 0.95. The fastening of the rod is articulated at both ends, length /== 3.0 m. Diameter of the log D= 180 mm. The ultimate flexibility of the rack Hmax-120.

Problem 5.8.

Select the reinforcement class and the diameters of the transverse bars for the reinforced concrete column, determine their pitch, if the longitudinal bars of the column frame are assumed to be 25 mm in diameter, A-III.

Problem 5.9.

Calculate reinforced concrete column. Load acting on the column, N= 640 kN; N(= 325 kN. Reliability factor for responsibility yn = 0.95. Load applied with random eccentricity. Column cross section 350x350 mm, symmetrical reinforcement. Column height H= 4.9 m, fastening of the ends of the column is hinged. Reinforcement - longitudinal class A- II, transverse Bp-1, heavy concrete class B20, yb2 - 0.9.

Problem 5.10.

Determine the reinforcement of a reinforced concrete column with a random eccentricity and design its cross section. Load: N- 1800 kN; N,= 1200 kN. Reliability coefficient for responsibility у„ - 0.95. The estimated length of the column / 0 = // skin! NY = 7.0 m.

Column cross section 400x400 mm. Concrete heavy class B30; yb2 - 0.9. Longitudinal and transverse reinforcement class A-III.

Problem 5.11.

Check the bearing capacity of a reinforced concrete column subjected to a load of N= 250 kN. Load applied

with random eccentricity; long part of the load A, = 125 kN; Reliability coefficient for liability у„ = 0.95. Estimated column length /0 = 3.0 m. Symmetrical reinforcement Ax = L5 = (2022 mm). fittings class A-Sh. Heavy concrete, concrete strength class B20; yy = 0.9. The section of the column is 300x400 mm (Fig. 5.39).

Problem 5.12.

Select the reinforcement of a reinforced concrete column with a random eccentricity. Estimated column length /0 = 6.0 m. Column cross section 400 x 500 mm. Reinforcement is symmetrical, A5-LE. Load: Ії= 700 kN, continuous part of the load 525 kN. coefficient

liability reliability factor y„ ~ 1.0. Heavy concrete class B25, coefficient of concrete working conditions yb2 = 0.9. Longitudinal reinforcement of class A-II, transverse reinforcement should be taken based on the required diameter, class A-I or Vr-1.

§ 6.5. Amplification Technology brick walls, pillars, piers

When reconstructing residential buildings with masonry walls, it becomes necessary to restore the bearing capacity or strengthen the masonry elements due to increased loads from the floors being built on. During long-term operation of buildings, signs of destruction of piers, pillars and masonry walls are observed as a result of uneven settlement of foundations, atmospheric influences, roof leaks, etc.

The process of restoring the bearing capacity of masonry should begin with the elimination of the main causes of cracking. If this process is facilitated by the uneven settlement of the building, then this phenomenon should be excluded by known and previously described methods.

Before making technical decisions on strengthening structures, it is important to evaluate the actual strength of the load-bearing elements. This assessment is carried out by the method of breaking loads, the actual strength of bricks, mortar, and for reinforced masonry- steel yield strength. In this case, it is necessary to fully take into account the factors that reduce the bearing capacity of structures. These include cracks, local damage, masonry deviations from the vertical, broken bonds, slab support, etc.

With regard to strengthening brickwork, the accumulated experience of reconstruction work allows us to identify a number of traditional technologies based on the use of: metal and reinforced concrete clips, frames; on the injection of polymer cement and other suspensions into the body of the masonry; on device monolithic belts on the upper part of buildings (in cases of superstructure), prestressed screeds and other solutions.

On fig. 6.40 shows typical design and technological solutions. The presented systems are aimed at comprehensive compression of walls using adjustable tension systems. They are made of open and closed types, with external and internal arrangement, they are provided with anti-corrosion protection.

Rice. 6.40. Structural and technological options for strengthening brick walls a- a scheme for strengthening the brick walls of the building with metal strands; b,in,G- nodes for placing metal strands; d- layout of a monolithic reinforced concrete belt; e- the same, strands with centering elements: 1 - metal cord; 2 - tension coupling: 3 - monolithic reinforced concrete belt; 4 - floor slab; 5 - anchor; 6 - centering frame; 7 - base plate with hinge

To create the required degree of tension, turnbuckles are used, access to which must always be open. They allow, as the strands lengthen as a result of temperature and other deformations, to produce additional tension. Compression of brick wall elements is carried out in places of greatest rigidity (corners, junctions of external and internal walls) through distribution plates.

For uniform compression of the wall masonry, a special design of the centering frame is used, which has a hinged support on the support-distribution plates. This solution ensures long-term operation with sufficiently high efficiency.

The locations of the tie rods and centering frames are closed various kinds belts and do not violate the general appearance of facade surfaces.

For elements of walls, piers, pillars that have destruction of the brickwork, but have not lost their stability, local replacement of the masonry is carried out. At the same time, the brand of brick is taken 1-2 units higher than the existing one.

The work production technology provides for: the arrangement of temporary unloading systems that perceive the load; dismantling of fragments of broken brickwork; masonry device. At the same time, it should be taken into account that the removal of temporary unloading systems should be carried out after the masonry strength has reached at least 0.7 R CL . As a rule, such restoration work is carried out while maintaining the structural design of the building and the actual loads.

Techniques for restoring unplastered brickwork are very effective when it is required to preserve the previous appearance of the facades. In this case, the brick is carefully selected according to the color scheme and size, as well as the material of the seams. After the restoration of the masonry, sandblasting is performed, which makes it possible to obtain updated surfaces where new sections of the masonry do not stand out from the main array.

Due to the fact that stone structures perceive mainly compressive forces, the most effective way to strengthen them is to install steel, reinforced concrete and reinforced cement clips. At the same time, the brickwork in the cage works under conditions of all-round compression, when the transverse deformations are significantly reduced and, as a result, the resistance to the longitudinal force increases.

The design force in the metal belt is determined by the dependence N= 0,2R KJl × l× b, where R KJl - design resistance of masonry to chipping, tf/m 2 ; l- length of the reinforced wall section, m; b- wall thickness, m

To provide normal operation brick walls and prevent further opening of cracks, the initial stage is to restore the bearing capacity of foundations by strengthening methods, which excludes the appearance of uneven settlement.

On fig. 6.41 shows the most common options for strengthening stone pillars and piers with steel, reinforced concrete and reinforced cement clips.

Rice. 6.41. Reinforcement of pillars with a steel cage (a), reinforcement cages (b), meshes and reinforced concrete cages ( in,G) 1 - reinforced structure; 2 - reinforcement elements; 3 - protective layer; 4 - panel formwork with clamps; 5 - injector; 6 - material hose

The steel cage consists of longitudinal angles for the entire height of the reinforced structure and transverse bars (clamps) made of flat or round steel. The step of the clamps is taken no more than a smaller section size, but no more than 500 mm. To include the clip in the work, the gaps between the steel elements and the masonry should be injected. The solidity of the structure is achieved by plastering with high-strength cement-sand mortars with the addition of plasticizers, which promote greater adhesion to masonry and metal structures.

For more effective protection, a metal or polymer mesh is installed on the steel cage, along which a solution with a thickness of 25-30 mm is applied. For small volumes of work, the mortar is applied manually using a plastering tool. Large volumes of work are performed mechanized with the supply of material by mortar pumps. To obtain a high-strength protective layer, gunning and pneumo-concreting installations are used. Due to the high density of the protective layer and high adhesion with masonry elements, the joint work of the structure is achieved and its bearing capacity is increased.

The device of a reinforced concrete jacket is carried out by installing reinforcing mesh along the perimeter of the reinforced structure with its fastening through clamps to the brickwork. Fastening is carried out by using anchors or dowels. Reinforced concrete clip is made of fine-grained concrete mix not lower than class B10 with longitudinal reinforcement of classes A240-A400 and transverse - A240. The step of transverse reinforcement is assumed to be no more than 15 cm. The thickness of the clip is determined by calculation and is 4-12 cm. Depending on the thickness of the clip, the technology of work production changes significantly. For clips up to 4 cm thick, methods of applying concrete by gunning and pneumoconcreting are used. The final finishing of surfaces is achieved by the device of a plaster covering layer.

For clips up to 12 cm thick, an inventory formwork is installed along the perimeter of the reinforced structure. Injection tubes are installed in its shields, through which a fine-grained concrete mixture is injected under a pressure of 0.2-0.6 MPa into the cavity. To improve adhesive properties and fill the entire space, concrete mixtures are plasticized by introducing superplasticizers in a volume of 1.0-1.2% of the mass of cement. Reducing the viscosity of the mixture and increasing its permeability are achieved by additional exposure to high-frequency vibration by contacting the vibrator with the formwork of the jacket. Pretty good effect.

gives a pulsed mode of supply of the mixture, when short-term exposure to increased pressure provides a higher velocity gradient and high permeability.

On fig. 6.41, G the technological scheme of production of works by injection of a reinforced concrete clip is given. The formwork is installed to the entire height of the structure with a protective layer of reinforcing filling. Injection of concrete is carried out in tiers (3-4 tiers). The process of finishing the supply of concrete is fixed by control holes on the opposite side from the place of injection. For accelerated hardening of concrete, systems of thermoactive formwork, heating wires and other methods of increasing the temperature of hardening concrete are used. Dismantling of the formwork is carried out in tiers when the concrete reaches the stripping strength. Hardening mode at t= 60 °С provides stripping strength during 8-12 hours of heating.

Reinforced concrete clips can be made in the form of fixed formwork elements (Fig. 6.42). In this case, the outer surfaces can have a shallow or deep relief or a smooth surface. After installing the fixed formwork and fixing its elements, the space between the reinforced and the enclosing structure is monolithic. The use of fixed formwork has a significant technological effect, since there is no need to dismantle the formwork, and most importantly, the finishing cycle of work is eliminated.

Rice. 6.42. Reinforcement of pillars using architectural concrete formwork 1 - reinforced structure; 2 - armored carcass; 3 - cladding elements; 4 - monolithic concrete

The most effective fixed formwork should be considered thin-walled elements (1.5-2 cm) made of dispersed-reinforced concrete. To involve the formwork in the work, it is equipped with protruding anchors, which significantly increase adhesion with the laid concrete.

The device of mortar clips differs from reinforced concrete in the thickness of the applied layer and composition. As a rule, to protect the reinforcing mesh and ensure its adhesion to the brickwork, cement-sand mortars are used with the addition of plasticizers that increase the physical and mechanical characteristics. The technology of construction processes practically does not differ from the performance of plastering works.

To provide joint work elements of the cage along its length, exceeding the thickness by 2 or more times, it is necessary to install additional cross-links through the section of the masonry. Reinforcing masonry can be done by injection. It is carried out by injecting cement or polymer cement mortar through pre-drilled holes. As a result, the solidity of the masonry is achieved and its physical and mechanical characteristics are increased.

Quite stringent requirements are imposed on injection solutions. They must have low water separation, low viscosity, high adhesion and sufficient strength characteristics. The solution is injected under pressure up to 0.6 MPa, which provides a fairly large penetration zone. Injection parameters: the location of the injectors, their depth, pressure, composition of the solution in each case are selected individually, taking into account the fracturing of the masonry, the state of the seams and other indicators.

The strength of injection-reinforced masonry is evaluated by SNiP II-22-81*"Stone and reinforced masonry structures". Depending on the nature of the defects and the type of injected solution, correction factors are set: mk = 1.1 - in the presence of cracks from force effects and when using cement and polymer cement mortars; tk\u003d 1.0 - in the presence of single cracks from uneven settlement or in case of a violation of the connection between the jointly working walls; mk = 1,3 - in the presence of cracks from force effects during the injection of polymer solutions. The strength of the solutions should be in the range of 15-25 MPa.

Strengthening brick lintels is a fairly common phenomenon, which is associated with a decrease in the bearing capacity of the spacer masonry due to weathering of the seams, adhesion failure and other reasons.

On fig. 6.43 shows constructive options for reinforcing jumpers using various kinds of metal plates. They are installed by punching grooves and holes in the brickwork and are subsequently monolithic with a cement-sand mortar along the grid.

Rice. 6.43. Examples of reinforcement of lintels of brick walls a,b- by summing up the overlays of angle steel; in,G- additional metal jumpers from the channel: 1 - brickwork; 2 - cracks; 3 - overlays from the corners; 4 - strip linings; 5 - anchor bolts; 6 - channel linings

To redistribute forces to reinforced concrete lintels due to increased loads on floors, metal unloading belts are used, made of two channels and combined with bolted connections.

Strengthening and increasing the stability of brick walls. The reinforcement technology is based on the creation of an additional reinforced concrete jacket on one or both sides of the wall (Fig. 6.44). The production technology includes the processes of preparing and cleaning the surface of the walls, drilling holes for anchors, installing anchors, attaching reinforcing bars or meshes to anchors, monolithic. As a rule, for sufficiently large volumes of work, a mechanized method of applying a cement-sand mortar is used: pneumoconcreting or shotcrete and less often manually. Then, to level the surfaces, a grout layer is applied and subsequent operations related to the finishing of the wall surfaces are performed.

Rice. 6.44. Strengthening brick walls with reinforcement a- individual reinforcement bars; b- reinforcing cages; in- reinforcing mesh; G- reinforced concrete pilasters: 1 - reinforced wall; 2 - anchors; 3 - fittings; 4 - plaster or shotcrete-concrete layer; 5 - metal strands; 6 - reinforcing mesh; 7 - armored carcass; 8 - concrete; 9 - formwork

An effective technique for reinforcing brick walls is the installation of reinforced concrete one- and two-sided racks in strebs and pilasters.

The technology for arranging double-sided reinforced concrete racks provides for the formation of grooves to a depth of 5-6 cm, drilling of through holes along the height of the wall, fastening with the help of reinforcing cage strands and subsequent solidification of the resulting cavity. For monolithic cement-sand mortars with plasticizing additives are used. A high effect is achieved when using mortars and fine-grained concretes with preliminary grinding of cement, sand and superplasticizer. Such mixtures, in addition to high adhesion, have the property of accelerated hardening and high physical and mechanical characteristics.

During the erection of one-sided reinforced concrete pilasters, a vertical bar is required, in the cavities of which anchor devices are installed. To the latter, the reinforcing cage is fastened. After its placement, the formwork is installed. It is carried out from separate plywood boards, united by clamps and attached to the wall with anchors. Fine-grained concrete mixture is pumped by pumps in tiers through holes in the formwork. A similar technology is used for double-sided pilasters, with the difference that the process of fastening the formwork panels is carried out with the help of bolts that cover the thickness of the wall.

Strengthening brick walls allows you to increase them performance characteristics. Very often you can see cracks in the walls brick house, which indicates their weakness and the presence of poor bearing support. Exist various methods reinforcement of brick walls to increase their resistance. The article will tell about some of them.

The basis for strengthening brick walls is their deformation, the reasons for which may be:

• Design errors. These include:

1. insufficient foundation depth;
2. unevenness in the settling of parts of the house;
3. deformations that have arisen in the beam covering;
4. discrepancy between the bearing capacity of the structure and the load on it.

• Exploitation. In this case, it might have happened:

1. waterlogging styling;
2. subsidence of the foundation.

• Errors that occurred during the laying of the walls.

Assessment of the degree of damage to brick walls, according to the loss of bearing capacity by elements, can be:

Weak - up to 15%. Due to:

1. defrosting;
2. the action of wind load;
3. damage to the wall material from fire to a depth of 5 millimeters;
4. oblique and vertical cracks intersecting in no more than two rows of masonry.

Average - up to 25%. Called:

1. weathering and defrosting masonry;
2. peeling of the facing material to a thickness of up to 25%;
3. brick damage from fire to a depth of two centimeters;
4. oblique and vertical cracks that intersect up to four rows of masonry;
5. buckling and inclination of walls on one floor, not exceeding a fifth of the thickness of the structure;
6. the formation of cracks at the intersection of transverse and longitudinal walls, caused by a violation of the masonry of the lintels and under the supports of the beams;
7. displacement of up to two centimeters of floor slabs.

High - up to 50%. This may occur due to:

1. wall collapse;
2. weathering and thawing of masonry up to 40% of its thickness;
3. damage to the wall material from fire to a depth of 6 centimeters:
4. oblique and vertical cracks, with the exception of temperature and sedimentary cracks, to a height of 7 rows of masonry;
5. bulging and tilting walls on one floor by one percent of its height;
6. displacements of racks and walls along an oblique groove or horizontal seams;
7. separation of longitudinal walls from transverse ones;
8. damage to the masonry under the racks of beams and lintels with a depth of more than 2 centimeters;
9. displacement of floor slabs on supports is more than 4 centimeters.

Tip: Walls that have lost more than 50% of their strength should be considered destroyed. The presence of the above damage is the basis for carrying out repair and restoration work.

How to strengthen brick walls

Repair and subsequent strengthening of brick walls, the schemes for its implementation can be very different, but in any case it is necessary:

• Repair the basement of the building.
• Seal cracks.
• Repair and strengthen jumpers.
• Strengthen individual piers and racks.
• Ensure the spatial rigidity of the walls.
• Perform a transfer to separate sections walls.
• Lay or arrange openings.
• Reinforce masonry walls by injection.

In brick houses, cracks can be:

• Narrow - 5 millimeters. Such defects are necessary:

1. embroider;
2. rinse with water;
3. minted with shotcrete.

• Wide - up to 40 millimeters, not violating the integrity of the masonry. Closed up in the same sequence as narrow cracks.
• More than 4 centimeters violate the integrity of the masonry. In this case the crack is:

1. cleared;
2. washed with water;
3. minted with shotcrete;
4. holes are drilled along the length of the crack;
5. injectors are inserted into the holes;
6. a special solution is pumped into the crack cavity under pressure.

On the diagram:

• 1 - a crack in the masonry.
• 2 - installation of injection holes.
• 3 - branch pipes for injections.
• 4 - a solution of cement and sand.

Walls out silicate brick can be strengthened in the following ways:

• The use of clips from reinforced solutions.
• Reinforcement of brick walls with steel strands.
• Installation of reinforced concrete clips around the perimeter of the building.
• The use of composite materials for clips.
• Reinforcement of brick walls with steel clips.

When choosing a home reinforcement method, you should consider a large number of factors.

It can be:

• A brand used for plaster, concrete or mortar.
• Percentage of building reinforcement.
• Wall masonry condition.
• Load diagram for the entire building.

The strength of brickwork depends directly on the percentage of reinforcement with its clamps.

At external examination can be assessed:

• Number of cracks.
• Their dimensions are depth and width.

Tip: To restore strength bearing walls lady, where there are cracks, it is necessary to reinforce them with clips.

How to make a reinforced clip

You can fix cracks and prevent the appearance of new defects with your own hands by reinforcing the walls (see).

For this are used:

• Reinforcing frames.
• Reinforcement bars.
• Reinforcing mesh.
• Reinforced concrete pilasters.

Instructions for reinforcing a wall with reinforcing mesh suggest:

• You can install the material on one or both sides, fixing the mesh on the repaired area.
• Holes are pre-drilled.
• The grid is fastened with through studs or anchor bolts included in these holes.
• Applied cement mortar, not lower than grade M100.
• A layer of plaster is applied with a thickness of 2 to 4 centimeters.
• Auxiliary rods with a diameter of 6 millimeters are attached, along the height of the corners, lowering the elements by about 30 centimeters to ensure their reinforcement.
• With one-sided fastening of the mesh, anchors with a diameter of 8 millimeters are placed in increments of up to 80 centimeters.
• With double-sided placement of the mesh, it is fastened with through anchors with a diameter of 12 millimeters in increments of up to 1.2 meters, welding or fastening to metal meshes.

How to install a reinforced concrete belt

A sand-lime brick wall can be reinforced with a reinforced concrete belt.

Its advantages:

• Saving time.
• Less price.

Flaw:

When using a reinforced concrete cage, such specifications, as:

• The thickness of the construction is from 4 to 12 centimeters.
• The concrete mixture is selected with a fine grain of at least grade 10.
• The transverse reinforcement is selected A240 / AI class, with an installation step of up to 15 centimeters.
• Longitudinal reinforcement is taken A240-A400 / AI, AII, AIII class.

For the manufacture of a reinforced concrete "shirt" structure, it is necessary to install around the entire perimeter reinforcing mesh, fixing it on the masonry with clamps.

Tip: To strengthen a brick wall, you should create a shell that exceeds the strength of the wall itself by several times.

The indicators of the effectiveness of the clip are:

• The condition of the laid surface.
• Strength of concrete.
• The nature of the load.
• percentage of reinforcement.

This type of construction takes on part of the load, freeing the masonry.

When making a frame:

• Layers up to 4 centimeters thick are performed by pneumoconcreting and gunning, and then plastering is performed.
• If the layers are up to 12 centimeters thick, the wall frame is made using an inventory formwork mounted around the reinforced base. Inventory formwork is installed along the entire height of the structure to be strengthened in order to protect the reinforcing layer. Injection tubes are arranged in the formwork, and a fine-grained concrete mixture is fed into them.

Composite clip features

The photo shows the construction of a clip from composite raw materials. This is one of the most effective methods for reinforcing brick walls, through the use of high-strength fibers: carbon and fiberglass.

They allow you to increase strength:

• For compression of sheer structures.
• On shear or shear of perpendicular sections.

Work technology:

• Prepared brickwork is treated with impregnation.
• A primer is applied to harden the surface.
• Metal frames are installed.
• Temporary fastenings are disassembled.

Tip: Temporary buildings should be removed after gaining 50% strength with new masonry, the value of which is indicated in the project.

• Walls are painted and plastered.

How to make a steel structure

The installation of a steel cage significantly increases the bearing capacity of the building.

To make it, you need to purchase:

• Reinforcing bars with a diameter of 12 millimeters.
• Transverse metal strips, section up to 6 centimeters wide, up to 12 millimeters thick.
• profile corners.

• On the solution at the corners of the area intended for reinforcement, vertical corners are installed.

• Strips are fastened with a step of no more than 50 centimeters.
• Longitudinal corners are selected with a length equal to the height of the reinforced structure.
• Applied to the corners metal grid to improve structural strength.
• The cement mortar must be up to 3 centimeters thick to protect the metal from corrosion.

Tip: When finishing large area, the process must be carried out using a mortar pump.

What modern methods are used to improve the strength of brick walls

Traditional methods using composite materials and injection, which quickly and effectively reinforce brick walls, can replace innovative ways of carrying out the process.

Its essence is as follows:

• Holes are drilled in the body of the building structure.
• They are pumped under pressure repair compounds, which can be:

1. microcements;
2. on epoxy resin;
3. based on polyurethane.

• The injection mixture fills the existing voids of the building structure, existing cracks, which prevents the destruction of the wall and provides reliable waterproofing of the building.

Wall injection allows:

• Fully fortify brickwork.
• Perform structural bonding of the material.
• Protect walls from the harmful effects of capillary moisture.

When reinforced with composite materials:

• Canvases (tapes or nets) made of high-strength material made on the basis of fiberglass or carbon are glued onto the building structure.
• Adhesives can be cement or epoxy based.

Reinforcement of masonry, reinforcement of openings in brick walls must be completed in full in order to restore absolutely all damaged areas. It is very important to carry out the reconstruction of the house in a timely manner in order to prevent the complete destruction of the walls. Any method, if performed correctly, strengthens the brickwork, increases the resistance of the building to loads, existing deformations and other factors. All the features of the work are shown in the video in this article.