BUILDINGS WITH LOAD-LOADING WALLS MADE OF BRICK OR MASONRY - SNiP II-7-81 CONSTRUCTION IN SEISMIC AREAS
3.35. Load-bearing brick and stone walls should be constructed, as a rule, from brick or stone panels or blocks manufactured in factories using vibration, or from brick or stone masonry using mortars with special additives that increase the adhesion of the mortar to the brick or stone.
With a calculated seismicity of 7 points, it is allowed to construct load-bearing walls of masonry buildings using mortars with plasticizers without the use of special additives that increase the adhesion strength of the mortar to brick or stone.
3.36. Carrying out brick and stone masonry manually at sub-zero temperatures for load-bearing and self-supporting walls (including those reinforced with reinforcement or reinforced concrete inclusions) with a calculated seismicity of 9 points or more is prohibited.
If the calculated seismicity is 8 points or less, winter masonry may be done manually with the obligatory inclusion of additives in the solution that ensure hardening of the solution at subzero temperatures.
3.37. Calculations of stone structures must be made for the simultaneous action of horizontally and vertically directed seismic forces.
The value of the vertical seismic load at a calculated seismicity of 7-8 points should be taken equal to 15%, and at a seismicity of 9 points - 30% of the corresponding vertical static load.
The direction of action of the vertical seismic load (up or down) should be taken as more unfavorable for the stress state of the element in question.
3.38. For laying load-bearing and self-supporting walls or filling the frame, the following products and materials should be used:
a) solid or hollow brick of grade no lower than 75 with holes up to 14 mm in size; with a calculated seismicity of 7 points, the use of ceramic stones of a grade not lower than 75 is allowed;
b) concrete stones, solid and hollow blocks (including those made of lightweight concrete with a density of at least 1200 kg/m3) grade 50 and higher;
a) stones or blocks made of shell rocks, limestones of grade no less than 35 or tuffs (except felsic) grade 50 and higher.
Piece masonry of walls should be carried out using mixed cement mortars of a grade not lower than 25 in summer conditions and not lower than 50 in winter conditions. For laying blocks and panels, a solution of a grade of at least 50 should be used.
3.39. Masonry is divided into categories depending on its resistance to seismic influences.
Category of brick or stone masonry made from materials provided for in clause 3.38. is determined by the temporary resistance to axial tension along untied seams (normal adhesion), the value of which should be within the limits:
To increase normal adhesion, solutions with special additives should be used.
The required value must be specified in the project. During design, the value should be assigned depending on the results of tests carried out in the construction area.
If it is impossible to obtain at the construction site (including with mortars with additives that increase the strength of their adhesion to brick or stone) a value equal to or exceeding 120 kPa (1.2 kgf/cm2), the use of brick or stone masonry is not allowed.
Note: With a calculated seismicity of 7 points, the use of natural stone masonry is allowed at less than 120 kPa (1.2 kgf/cm2), but not less than 60 kPa (0.6 kgf/cm2) . In this case, the height of the building should be no more than three floors, the width of the walls should be at least 0.9 m, the width of the openings is no more than 2 m, and the distance between the axes of the walls is no more than 12 m.
The masonry project must include special measures for the care of hardening masonry, taking into account the climatic characteristics of the construction area. These measures should ensure that the required strength indicators of the masonry are obtained.
3.40. Design resistance values for masonry R R, R Wed, R ch for untied seams should be taken according to SNiP for the design of stone and reinforced masonry structures, and for untied seams - determined according to formulas (9) - (11) depending on the value obtained as a result of tests carried out in the construction area:
R hl = 0.8 (11)
Values R R, R Wed and R hl should not exceed the corresponding values when destroying brick or stone masonry.
3.41. The height of the floor of buildings with load-bearing walls made of brick or stone masonry, not reinforced with reinforcement or reinforced concrete inclusions, should not exceed, with a calculated seismicity of 7, 8 and 9 points, respectively 5; 4 and 3.5 m.
When strengthening the masonry with reinforcement or reinforced concrete inclusions, the floor height can be taken respectively equal to 6; 5 and 4.5 m.
In this case, the ratio of the floor height to the wall thickness should be no more than 12.
3.42. In buildings with load-bearing walls, in addition to external longitudinal walls, as a rule, there must be at least one internal longitudinal wall. The distances between the axes of transverse walls or frames replacing them must be checked by calculation and be no more than those given in Table 9.
Table 9
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Distances, m, at calculated seismicity, points |
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Note: It is allowed to increase the distances between walls made of complex structures by 30% compared to those indicated in Table 9.
3.43. The dimensions of the wall elements of stone buildings should be determined by calculation. They must meet the requirements given in table. 10.
3.44. At the level of floors and coverings, anti-seismic belts should be installed along all longitudinal and transverse walls, made of monolithic reinforced concrete or prefabricated with monolithic joints and continuous reinforcement. Anti-seismic belts of the upper floor must be connected to the masonry by vertical outlets of reinforcement.
In buildings with monolithic reinforced concrete floors embedded along the contours of the walls, anti-seismic belts at the level of these floors may not be installed.
3.45. The antiseismic belt (with a supporting section of the floor) should, as a rule, be installed across the entire width of the wall; in external walls with a thickness of 500 mm or more, the width of the belt can be 100-150 mm less. The height of the belt must be at least 150 mm, the grade of concrete must be at least 150.
Anti-seismic belts must have longitudinal reinforcement 4 d 10 with a calculated seismicity of 7-8 points and not less than 4 d 12 - at 9 points.
3.46. At the junctions of walls, reinforcing meshes with a total cross-sectional area of longitudinal reinforcement of at least 1 cm 2, a length of 1.5 m, every 700 mm in height with a calculated seismicity of 7-8 points and after 500 mm - with 9 points, must be laid in the masonry.
Sections of walls and pillars above the attic floor, having a height of more than 400 mm, must be reinforced or reinforced with monolithic reinforced concrete inclusions anchored in an anti-seismic belt.
Brick pillars are allowed only with a calculated seismicity of 7 points. In this case, the grade of mortar should be no lower than 50, and the height of the pillars should not be more than 4 m. The pillars should be connected in two directions by beams anchored into the walls.
3.47. The seismic resistance of the stone walls of a building should be increased by using reinforcement meshes, creating an integrated structure, prestressing the masonry, or other experimentally proven methods.
Vertical reinforced concrete elements (cores) must be connected to anti-seismic belts.
Reinforced concrete inclusions in the masonry of complex structures should be open on at least one side.
Table 10
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Wall element |
Wall element size, m, at calculated seismicity, points |
Notes |
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1. The width of the corner partitions should be taken at 25 cm 1. The width of the partitions, not less than, m, when laying: 7 |
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more than indicated in the table. |
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2. Partitions of smaller width must be reinforced with reinforced concrete framing or reinforcement |
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2. Width of openings, m, no more, for masonry of category I or II |
Openings of larger width should be bordered with a reinforced concrete frame |
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3. Ratio of the width of the wall to the width of the opening, not less |
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4. Protrusion of walls in plan, no more, m |
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5. Removal of cornices, no more, m: |
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0,20,2 from wall material |
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from reinforced concrete elements connected with anti-seismic belts 0.2 |
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wooden, plastered over metal mesh |
Removal of wooden unplastered cornices is allowed up to 1 m |
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When designing complex structures as frame systems, anti-seismic belts and their interfaces with the racks must be calculated and designed as frame elements, taking into account the filling work. In this case, the grooves provided for concreting the racks must be open on at least two sides. If complex structures are made with reinforced concrete inclusions at the ends of the walls, the longitudinal reinforcement must be securely connected with clamps laid in the horizontal joints of the masonry. Concrete inclusions must be no lower than grade 150, masonry must be done with a mortar of grade no lower than 50, and the amount of longitudinal reinforcement should not exceed 0.8% of the cross-sectional area of the concrete walls.
Note: The load-bearing capacity of reinforced concrete inclusions located at the ends of the piers, taken into account when calculating seismic effects, should not be taken into account when calculating sections for the main combination of loads.
3.48. In buildings with load-bearing walls, the first floors used for shops and other premises that require large free space should be made of reinforced concrete structures.
3.49. Lintels should, as a rule, be installed over the entire thickness of the wall and embedded in the masonry to a depth of at least 350 mm. With an opening width of up to 1.5 m, sealing of lintels is allowed at 250 mm.
3.50. Beams for staircase landings should be embedded in the masonry to a depth of at least 250 mm and anchored.
It is necessary to provide for the fastening of steps, stringers, prefabricated flights, and the connection of landings with floors. The construction of cantilever steps embedded in masonry is not allowed. Door and window openings in the stone walls of staircases with a calculated seismicity of 8-9 points should, as a rule, have a reinforced concrete frame.
3.51. In buildings with a height of three or more floors with load-bearing walls made of brick or masonry with a calculated seismicity of 9 points, exits from stairwells should be arranged on both sides of the building.
1. For laying load-bearing and self-supporting walls and filling the frame, you must use:
Solid or hollow brick of grade no lower than 75 with holes up to 14 mm in size;
Concrete stones, solid and hollow blocks of grade 50 and higher, including lightweight concrete with a density of at least 1200 kg/m 3 ;
Stones and blocks made of shell rock, limestone grade no less than 35 or tuff grade 50 and higher.
For construction in seismic areas, the use of stones with large voids and thin walls, and masonry with backfill is prohibited.
2. Masonry of walls made of bricks and small blocks should be carried out using complex masonry mortars of a grade not lower than 25 in conditions of positive outside temperatures and not lower than 50 in conditions of negative temperatures, and masonry of large blocks should be carried out using mortars of a grade not lower than 50.
The use of slag Portland cement and pozzolanic Portland cement for the preparation of polymer cement mortars is not allowed.
3. Anti-seismic joints in the masonry must be made by erecting paired walls. The width of the seams is determined by calculation, but it should not be less than:
For building heights up to 5 m - 30 mm;
For higher building heights, the height is increased by 20 mm for every 5 m.
Anti-seismic joints should not have fillings that would prevent mutual movements of building compartments. If necessary, it is allowed to cover anti-seismic seams with aprons or seal them with flexible materials.
4. The dimensions of the wall elements of stone buildings should be determined by calculation, but they should not be less than the values given in the table. 3.
Table 3
(SNiP 3.03.01-87)
Corner partitions are made 25 cm wider than indicated in the table. 3. When constructing openings exceeding
dimensions given in table. 3, they must be surrounded by a reinforced concrete frame.
5. Horizontal masonry joints must be reinforced with mesh in compliance with the requirements given in SNiP-N-7-81* and this section.
For horizontal reinforcement of solid sections of walls and piers made of brick or small blocks, meshes with longitudinal reinforcement with a diameter of 5-6 mm with transverse rods with a diameter of 3-4 mm, located at a distance of no more than 40 cm from each other, should be used. Reinforcement should be carried out at least every 5 rows of bricks or every 40 cm along the height of masonry made of small blocks or stones.
The junction of stone walls is reinforced with meshes with a total cross-sectional area of longitudinal reinforcement of at least 1 cm2, a length of 1.5 m every 700 mm in height with a calculated seismicity of 7-8 points and after 500 mm - with 9 points.
6. All types of masonry must have vertical reinforcement or include vertical reinforced concrete elements made of concrete of class not lower than B12.5, the reinforcement of which is connected to anti-seismic belts in accordance with SNiP II-7-81*.
Reinforced concrete inclusions in masonry must be made open on at least one side in order to ensure control over the quality of their concreting. They are connected to the masonry using reinforcing mesh (3-4 Ø 0 6 mm A-1), running them into the masonry 70 cm and positioned at the same spacing as the joint reinforcement.
Reinforced concrete inclusions (cores) are connected to the masonry with closed clamps with a diameter of 5-6 mm, which are placed in horizontal joints of the masonry and brought to the depth of the wall:
If the ratio of its height to width is more than 1 - over the entire width in increments of at least 40 cm for 9-point calculated seismicity, up to 65 cm for 7-8-point seismicity;
When the ratio is less than 1 - at a distance of at least 50 cm with a similar step at the corresponding calculated seismicity.
7. Reinforced concrete anti-seismic belts in the level of floors and coverings along all longitudinal and transverse walls are made with a wall thickness of up to 50 cm equal to their thickness, and with a thickness of more than 50 cm it is allowed to install belts 10-15 cm wide less than the thickness of the walls.
8. The height of reinforced concrete belts must be at least 15 cm. The cross-section of their longitudinal reinforcement is determined by calculation.
9. Lintels in the walls must be installed to their full thickness and embedded in the masonry to a depth of at least 350 mm on both sides. With an opening width of up to 1.5 m, sealing of lintels is allowed at 250 mm.
Masonry of walls made of small-piece stone materials must be carried out in compliance with the following requirements:
Masonry should be done using single-row (chain) dressing;
All masonry joints should be filled completely with mortar, with the mortar trimmed on the outer sides of the masonry;
Temporary (installation) breaks in the masonry being erected should be terminated only with an inclined groove and located outside the areas of structural reinforcement of the walls.
10. Monitoring the strength of normal adhesion of the solution should be performed at the age of 7 days. The adhesion value should be 50% of the strength at the age of 28 days. If the strength does not correspond to the design value, it is necessary to stop the work until the issue is resolved by the design organization.
ElenaRudenkaya (Builderclub expert)Good afternoon.
Of course, a monolithic belt is required in order to just support the slabs and evenly distribute the load from the upper structures.
The parameters of the armored belt are as follows: the armored belt is 20-25 cm high in front of the 1st floor and the roof along all load-bearing walls, solid and closed. The width of the belt depends on the thickness of the load-bearing wall, as I understand it, the width is 250 mm and external load-bearing and 250 mm transverse load-bearing (internal).
Reinforcement of the reinforced belt: 4 rods of longitudinal reinforcement Ø12 mm, laid in 2 rows (2 rods in each row), connected by transverse reinforcement (clamps) Ø8 mm with a pitch of 30 cm. The distance of the reinforcement from the edge of the concrete is 5 cm. Sectional diagram :
Some information about armored belts:
Reinforced belts increase the overall stability of the building and the strength of the walls, especially under seismic loads. The armored belt also allows you to support heavy wooden or metal metal structures (beams, channels, I-beams, etc.) to create floors in the house, under which walls made of light materials could be deformed. When the roof is supported on a monolithic belt (usually through a Mauerlat), it is able to absorb part of the thrust and load from the roof. With a reinforced belt, for example, it does not squeeze out the masonry with rafter legs when the roof is overloaded. Reinforced house hoops perform the same function as metal hoops for a wooden barrel, which connect the wooden parts into a single shape and carry the load.
A reinforced belt is necessary for:
- Ensuring the rigidity and stability of walls and foundations;
- If necessary, to increase the support area of the ceiling and other structures;
- To evenly distribute the load on the walls of the lower floor from the walls of the upper floor, beams or roof.
- With a well-made armored belt, the rigidity of the walls increases significantly. Accordingly, the resistance to deformation during new construction of a house increases. And the armored belt allows you to avoid uneven shrinkage of the building and the formation of cracks from deforming loads (uneven settlement of the soil under the structure, seasonal and daily temperature changes).
- Sometimes builders lay masonry poorly. And when it is installed, the level of the top row between floors or under the roof shifts greatly (the corners of the house can be made at different levels). The armored belt allows you to level the masonry of the next floor, or the top of the masonry, before erecting the roof, due to the mobility of the concrete mixture strictly in the horizontal plane. That is, you can level the level of a floor or roof using concrete, adding more of it in the problem area.
- From point loads under heavy steel or reinforced concrete beams, as well as due to distortions when laying floor slabs or other heavy structures.
Ask.
answer
when the pitch of wall columns of the frame is no more than 6 m;
when the height of the walls of buildings erected on sites with seismicity 7, 8 and 9 points, respectively, is not more than 18, 16 and 9 m.
3.24. The masonry of self-supporting walls in frame buildings must be of category I or II (according to clause 3.39), have flexible connections with the frame that do not prevent horizontal displacements of the frame along the walls.
A gap of at least 20 mm must be provided between the surfaces of the walls and columns of the frame. Anti-seismic belts connected to the building frame should be installed along the entire length of the wall at the level of the covering slabs and the top of the window openings.
At the intersections of end and transverse walls with longitudinal walls, anti-seismic joints must be installed to the entire height of the walls.
3.25. Staircase and elevator shafts of frame buildings should be constructed as built-in structures with floor-to-floor sections that do not affect the rigidity of the frame, or as a rigid core that absorbs seismic loads.
For frame buildings up to 5 floors high with a calculated seismicity of 7 and 8 points, it is allowed to arrange staircases and elevator shafts within the building plan in the form of structures separated from the building frame. The construction of staircases in the form of separate structures is not permitted.
3.26. For supporting structures of tall buildings (more than 16 floors), frames with diaphragms, bracing or stiffening cores should be used.
When choosing structural schemes, preference should be given to schemes in which zones of plasticity arise primarily in the horizontal elements of the frame (crossbars, lintels, strapping beams, etc.).
3.27. When designing high ranks, in addition to bending and shear deformations in the frame struts, it is necessary to take into account axial deformations, as well as the compliance of the foundations, and carry out calculations for stability against overturning.
3.28. On sites composed of category III soils (according to Table 1*), the construction of high knowledge, as well as buildings indicated in pos. 4 tables 4. not allowed.
3.29. The foundations of tall buildings on non-rocky soils should, as a rule, be made of piles or in the form of a continuous foundation slab.
LARGE PANEL BUILDINGS
3.30. Large-panel buildings should be designed with longitudinal and transverse walls, combined with each other and with floors and coverings into a single spatial system that can withstand seismic loads.
When designing large-panel buildings it is necessary:
Wall and ceiling panels should, as a rule, be room sized;
provide for the connection of wall and ceiling panels by welding reinforcement outlets, anchor rods and embedded parts and embedding vertical wells and joint areas along horizontal seams with fine-grained concrete with reduced shrinkage;
when supporting the floors on the external walls of the building and on the walls at expansion joints, provide welded connections between the reinforcement outlets from the floor panels and the vertical reinforcement of the wall panels.
3.31. Reinforcement of wall panels should be done in the form of spatial frames or welded reinforcing mesh. In the case of using three-layer external wall panels, the thickness of the internal load-bearing concrete layer should be at least 100 mm.
3.32. The constructive solution of horizontal butt joints must ensure the perception of the calculated values of forces in the seams. The required cross-section of metal connections in the seams between the panels is determined by calculation, but it should not be less than 1 cm2 per 1 m of seam length, and for buildings with a height of 5 floors or less, with a site seismicity of 7 and 8 points, not less than 0.5 cm2 per 1 m of length seam It is allowed to place no more than 65% of the vertical design reinforcement at the intersections of the walls.
3.33. Walls along the entire length and width of the building should, as a rule, be continuous.
3.34. Loggias should, as a rule, be built-in, with a length equal to the distance between adjacent walls. Where loggias are located in the plane of external walls, reinforced concrete frames should be installed.
The installation of bay windows is not permitted.
BUILDINGS WITH LOAD-LOADING WALLS MADE OF BRICK OR MASONRY
3.35. Load-bearing brick and stone walls should be constructed, as a rule, from brick or stone panels or blocks manufactured in factories using vibration, or from brick or stone masonry using mortars with special additives that increase the adhesion of the mortar to the brick or stone.
With a calculated seismicity of 7 points, it is allowed to construct load-bearing walls of masonry buildings using mortars with plasticizers without the use of special additives that increase the adhesion strength of the mortar to brick or stone.
3.36. Carrying out brick and stone masonry manually at sub-zero temperatures for load-bearing and self-supporting walls (including those reinforced with reinforcement or reinforced concrete inclusions) with a calculated seismicity of 9 points or more is prohibited.
If the calculated seismicity is 8 points or less, winter masonry may be done manually with the obligatory inclusion of additives in the solution that ensure hardening of the solution at subzero temperatures.
3.37. Calculations of stone structures must be made for the simultaneous action of horizontally and vertically directed seismic forces.
The value of the vertical seismic load at a calculated seismicity of 7-8 points should be taken equal to 15%, and at a seismicity of 9 points - 30% of the corresponding vertical static load.
The direction of action of the vertical seismic load (up or down) should be taken as more unfavorable for the stress state of the element in question.
3.38. For laying load-bearing and self-supporting walls or filling the frame, the following products and materials should be used:
a) solid or hollow brick of grade no lower than 75 with holes up to 14 mm in size; with a calculated seismicity of 7 points, the use of ceramic stones of a grade not lower than 75 is allowed;
b) concrete stones, solid and hollow blocks (including those made of lightweight concrete with a density of at least 1200 kg/m3) grade 50 and higher;
a) stones or blocks made of shell rocks, limestones of grade no less than 35 or tuffs (except felsic) grade 50 and higher.
Piece masonry of walls should be carried out using mixed cement mortars of a grade not lower than 25 in summer conditions and not lower than 50 in winter conditions. For laying blocks and panels, a solution of a grade of at least 50 should be used.
3.39. Masonry is divided into categories depending on its resistance to seismic influences.
Category of brick or stone masonry made from materials provided for in clause 3.38. is determined by the temporary resistance to axial tension along untied seams (normal adhesion), the value of which should be within the limits:
To increase normal adhesion https://pandia.ru/text/78/304/images/image016_13.gif" width="16" height="21 src="> must be specified in the project..gif" width="18" height="23"> equal to or exceeding 120 kPa (1.2 kgf/cm2), the use of brick or stone masonry is not allowed.
Note..gif" width="17 height=22" height="22"> obtained as a result of tests carried out in the construction area:
R p = 0.45 (9)
R Wed = 0,7 (10)
R hl = 0.8 (11)
Values R R, R Wed and R hl should not exceed the corresponding values when destroying brick or stone masonry.
3.41. The height of the floor of buildings with load-bearing walls made of brick or stone masonry, not reinforced with reinforcement or reinforced concrete inclusions, should not exceed 5, 4 and 3.5 m with a calculated seismicity of 7, 8 and 9 points, respectively.
When strengthening the masonry with reinforcement or reinforced concrete inclusions, the floor height can be taken equal to 6, 5 and 4.5 m, respectively.
In this case, the ratio of the floor height to the wall thickness should be no more than 12.
3.42. In buildings with load-bearing walls, in addition to external longitudinal walls, as a rule, there must be at least one internal longitudinal wall. The distances between the axes of transverse walls or frames replacing them must be checked by calculation and be no more than those given in Table 9.
Table 9
Distances, m, at calculated seismicity, points |
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Note: It is allowed to increase the distances between walls made of complex structures by 30% compared to those indicated in Table 9.
3.43. The dimensions of the wall elements of stone buildings should be determined by calculation. They must meet the requirements given in table. 10.
3.44. At the level of floors and coverings, anti-seismic belts should be installed along all longitudinal and transverse walls, made of monolithic reinforced concrete or prefabricated with monolithic joints and continuous reinforcement. Anti-seismic belts of the upper floor must be connected to the masonry by vertical outlets of reinforcement.
In buildings with monolithic reinforced concrete floors embedded along the contours of the walls, anti-seismic belts at the level of these floors may not be installed.
3.45. The antiseismic belt (with a supporting section of the floor) should, as a rule, be installed across the entire width of the wall; in external walls with a thickness of 500 mm or more, the width of the belt can be 100-150 mm less. The height of the belt should be at least 150 mm, grade of concrete 1 - not lower than 150.
Anti-seismic belts must have longitudinal reinforcement 4 d l0 with a calculated seismicity of 7-8 points and not less than 4 d 12 - at 9 points.
3.46. At the junctions of the walls, reinforcing mesh with a cross-section of longitudinal reinforcement with a total area of at least 1 cm2, a length of 1.5 m must be placed in the masonry every 700 mm in height with a calculated seismicity of 7-8 points and after 500 mm - with 9 points.
Sections of walls and pillars above the attic floor, having a height of more than 400 mm, must be reinforced or reinforced with monolithic reinforced concrete inclusions anchored in an anti-seismic belt.
Brick pillars are allowed only with a calculated seismicity of 7 points. In this case, the grade of mortar should be no lower than 50, and the height of the pillars should not be more than 4 m. The pillars should be connected in two directions by beams anchored into the walls.
3.47. The seismic resistance of the stone walls of a building should be increased by using reinforcement meshes, creating an integrated structure, prestressing the masonry, or other experimentally proven methods.
Vertical reinforced concrete elements (cores) must be connected to anti-seismic belts.
Reinforced concrete inclusions in the masonry of complex structures should be made open on at least one side.
Table 10
Wall element | Wall element size, m, at calculated seismicity, points | Notes |
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Partitions with a width of at least m, when laying: | The width of the corner walls should be taken 25 cm more than indicated in the table. Partitions of smaller width must be reinforced with reinforced concrete framing or reinforcement |
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2. Openings with a width of no more than m, for masonry of category I or II | Openings of larger width should be bordered with a reinforced concrete frame |
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3. Ratio of the width of the wall to the width of the opening, not less | ||||
4. Protrusion of walls in plan, no more, m | ||||
5. Removal of cornices, no more, m: | Removal of unplastered wooden |
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from wall material | cornices allowed |
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from reinforced concrete elements connected with anti-seismic belts | ||||
wooden, plastered over metal mesh |
When designing complex structures as frame systems, anti-seismic belts and their interfaces with the racks must be calculated and designed as frame elements, taking into account the filling work. In this case, the grooves provided for concreting the racks must be open on at least two sides. If complex structures are made with reinforced concrete inclusions at the ends of the walls, the longitudinal reinforcement must be securely connected with clamps laid in the horizontal joints of the masonry. Concrete inclusions must be no lower than grade 150, rolling must be carried out with a solution of grade no lower than 50, and the amount of longitudinal reinforcement should not exceed 0.8% of the cross-sectional area of the concrete walls.
Note: The load-bearing capacity of reinforced concrete inclusions located at the ends of the piers, taken into account when calculating seismic effects, should not be taken into account when calculating sections for the main combination of loads.
3.48. In buildings with load-bearing walls, the first floors used for shops and other premises that require large free space should be made of reinforced concrete structures.
3.49. Lintels should, as a rule, be installed over the entire thickness of the wall and embedded in the masonry to a depth of at least 350 mm. With an opening width of up to 1.5 m, sealing of lintels is allowed at 250 mm.
3.50. Beams for staircase landings should be embedded in the masonry to a depth of at least 250 mm and anchored.
It is necessary to provide for the fastening of steps, stringers, prefabricated flights, and the connection of landings with floors. The construction of cantilever steps embedded in masonry is not allowed. Door and window openings in the chamber walls of staircases with a calculated seismicity of 8-9 points should, as a rule, have a reinforced concrete frame.
3.51. In buildings with a height of three or more floors with load-bearing walls made of brick or masonry with a calculated seismicity of 9 points, exits from stairwells should be arranged on both sides of the building.
REINFORCED CONCRETE STRUCTURES
3.52. When calculating the strength of normal sections of bent and eccentrically compressed elements, the limiting characteristic of the compressed zone of concrete should be taken according to SNiP for the design of concrete and reinforced concrete structures with a coefficient of 0.85.
3.53. In eccentrically compressed elements, as well as in the compressed zone of bending elements with a calculated seismicity of 8 and 9 points, clamps should be installed according to calculations at distances: at R ac 400 MPa (4000 kgf/cm2) - no more than 400 mm and with knitted frames - no more than 12 d, and with welded frames - no more than 15 d at R ac ³ 450 MPa (4500 kgf/cm2) - no more than 300 mm and with knitted frames - no more than 10 d, and with welded frames - no more than 12 d, Where d- the smallest diameter of compressed longitudinal rods. In this case, the transverse reinforcement must ensure fastening of the compressed rods from bending in any direction.
The distances between clamps of eccentrically compressed elements in places where working reinforcement is overlapped without welding should be taken no more than 8 d.
If the total saturation of an eccentrically compressed element with longitudinal reinforcement exceeds 3%, the clamps should be installed at a distance of no more than 8 d and no more than 250mm.
3.54. In columns of frame frames of multi-storey buildings with a design seismicity of 8 and 9 points, the spacing of clamps (except for the requirements set out in clause 3.53) should not exceed 1/2 h, and for frames with load-bearing diaphragms - no more h, Where h- the smallest side size of columns of rectangular or I-section. The diameter of the clamps in this case should be at least 8 mm.
3.55. In knitted frames, the ends of the clamps must be bent around the longitudinal reinforcement rod and inserted into the concrete core by at least 6 d clamp.
3.56. Elements of prefabricated columns of multi-story frame buildings should, if possible, be enlarged into several floors. The joints of precast columns must be located in an area with lower bending moments. Overlapping longitudinal reinforcement of columns without welding is not allowed.
3.57. In prestressed structures subject to design for a special combination of loads taking into account seismic effects, the forces determined from the strength conditions of the sections must exceed the forces absorbed by the section during the formation of cracks by at least 25% .
3.58. In prestressed structures, it is not allowed to use reinforcement for which the relative elongation after rupture is below 2%.
3.59. In buildings and structures with a calculated seismicity of 9 points without special anchors, it is not allowed to use reinforcing ropes and periodic profile rod reinforcement with a diameter of more than 28 mm.
3.60. In prestressed structures with reinforcement tensioned on concrete, the prestressed reinforcement should be placed in closed channels, which are subsequently sealed with concrete or mortar.
4. TRANSPORT FACILITIES
GENERAL PROVISIONS
4.1. The instructions in this section apply to the design of railways of I-IV categories, highways of I-IV, IIIp and IVp categories, subways, high-speed city roads and main streets running in areas with seismicity of 7, 8 and 9 points.
Notes: 1. Production, auxiliary, warehouse and other buildings for transport purposes should be designed according to the instructions in sections 2 and 3.
2. When designing structures on category V railways and on railway tracks of industrial enterprises, seismic loads may be taken into account in agreement with the organization approving the project.
4.2. This section establishes special requirements for the design of transport structures with a design seismicity of 7, 8 and 9 points. The calculated seismicity for transport structures is determined according to the instructions in paragraph 4.3.
4.3. Projects for tunnels and bridges with a length of more than 500 m should be developed based on the calculated seismicity, established in agreement with the organization approving the project, taking into account data from special engineering and seismological studies.
The calculated seismicity for tunnels and bridges with a length of no more than 500 m and other artificial structures on railways and highways of categories I-III, as well as on high-speed city roads and main streets is assumed to be equal to the seismicity of construction sites, but not more than 9 points.
The calculated seismicity for artificial structures on railways of IV-V categories, on railway tracks of industrial enterprises and on roads of IV, IIIï and IVï categories, as well as for embankments, excavations, ventilation and drainage tunnels on roads of all categories is taken as one point lower than seismicity construction sites.
Note: The seismicity of construction sites for tunnels and bridges not exceeding 500 m in length and other artificial road structures, as well as the seismicity of embankment and excavation construction sites, as a rule, should be determined on the basis of data from general engineering and geological surveys according to Table 1*, taking into account the additional requirements set out in clause 4.4.
4.4. During surveys for the construction of transport structures erected on sites with special engineering-geological conditions (sites with complex terrain and geology, river beds and floodplains, underground workings, etc.), and when designing these structures, coarse, low-moisture soils from igneous rocks containing 30% of sand-clay filler, as well as dense gravelly and medium-density water-saturated sands, should be classified as category II soils according to seismic properties; clay soils with a consistency index of 0.25< IL£ 0.5 at porosity factor e< 0.9 for clays and loams and e < 0,7 для супесей - к грунтам III категории.
Notes. The seismicity of tunnel construction sites should be determined depending on the seismic properties of the soil in which the tunnel is embedded.
2. The seismicity of construction sites for bridge supports and retaining walls with shallow foundations should be determined depending on the seismic properties of the soil located at the foundation marks.
3. The seismicity of construction sites for bridge supports with deep foundations, as a rule, should be determined depending on the seismic properties of the soil of the upper 10-meter layer, counting from the natural surface of the soil, and when cutting the soil - from the surface of the soil after cutting. In cases where the calculation of a structure takes into account the inertial forces of the soil masses cut through by the foundation, the seismicity of the construction site is established depending on the seismic properties of the soil located at the foundation marks.
4. The seismicity of construction sites for embankments and pipes under embankments should be determined depending on the seismic properties of the soil of the upper 10-meter layer of the embankment base.
5. The seismicity of excavation construction sites can be determined depending on the seismic properties of the soil of a 10-meter layer, counting from the contour of the excavation slopes.
ROAD ROUTING
4.5. When tracing roads in areas with seismicity of 7, 8 and 9 points, as a rule, it is necessary to avoid areas that are particularly unfavorable in engineering and geological terms, in particular areas of possible landslides, landslides and avalanches.
4.6. The routing of roads in areas with seismicity of 8 and 9 points on non-rocky slopes with a slope steepness of more than 1:1.5 is allowed only on the basis of the results of special engineering-geological surveys. Routing roads along non-rocky slopes with a steepness of 1:1 or more is not allowed.
SUBSTRATE AND UPPER STRUCTURE OF THE WAY
4.7. When the calculated seismicity is 9 points and the height of the embankments (depth of excavations) is more than 4 m, the slopes of the subgrade made of non-rocky soils should be taken at 1:0.25 position of the slopes designed for non-seismic areas. Slopes with a steepness of 1:2.25 and less steep can be designed according to the standards for non-seismic areas.
Slopes of excavations and half-excavations located in rocky soils, as well as slopes of embankments made of coarse-grained soils containing less than 20% by weight of filler, can be designed according to the standards for non-seismic areas.
For laying brick (stone) walls, a single-row chain ligation system should be used. On sites with a seismicity of 7 points, the use of a multi-row ligation system is allowed, while the bonded rows of masonry must be arranged at least after three spoon rows.
In seismic areas, the use of lightweight masonry with internal heat-insulating layers in load-bearing and self-supporting walls is not allowed.
For laying load-bearing and self-supporting walls, the following products and materials should be used:
a) fired solid or hollow brick of grade 75 and higher with vertical holes with a diameter of no more than 16 mm and a voidness of no more than 25%;
b) ceramic stones of grade no lower than 100 with vertical holes with a diameter of no more than 16 mm and a voidness of no more than 25%;
c) solid concrete stones and small blocks of heavy and light concrete of class not lower than B3.5;
d) if the seismicity of the construction site is 7 points, it is allowed to use ceramic stones of a grade not lower than 75 with vertical slot voids up to 12 mm wide and a voidness of no more than 25%.
The walls must be laid using mixed cement mortars of grade no lower than 50.
The use of stones and small blocks of regular shape from natural materials (shell rocks, limestones, tuffs, sandstones), hollow concrete stones and blocks, solid blocks of cellular concrete of class below B3.5, bricks and stones, in the masonry of load-bearing and self-supporting walls
manufactured using non-firing technology must be carried out in accordance with regulatory and instructional documents developed in the development of these standards.
The construction of load-bearing and self-supporting walls (including those reinforced with reinforcement or reinforced concrete inclusions) at negative temperatures in brick (stone) masonry when the seismicity of construction sites is 9 and 10 points is prohibited.
If the seismicity of construction sites is 7 and 8 points, winter masonry is allowed with the mandatory inclusion of additives in the mortar that ensure hardening of the mortar at subzero temperatures.
In seismic areas, the use of baked brick or ceramic stone with horizontal (parallel to the masonry bed) voids is not allowed.
The value of the temporary resistance of brick (stone) masonry to axial tension along untied seams (normal adhesion - Rnl) for load-bearing and self-supporting walls it must be at least 120 kPa (1.2 kgf/cm2).
To increase the normal adhesion of masonry, solutions with special additives should be used.
Design resistance values for masonry Rtl(axial tension), R(slice) and Rnl(tension during bending) along tied seams should be taken in accordance with the instructions of building codes for the design of stone and reinforced masonry structures, and for untied seams - determined according to formulas (7.1-7.3) SNiP RK 2.03-30-2006, depending on the value Rnt obtained during tests carried out in the construction area:
R =0.45Rnt (7.1)
R sq =0.7R nt (7.2)
Rtb =0.8Rnt (7.3)
Values R f R sq And Rtb should not exceed the corresponding values obtained when destroying brick or stone masonry.
Required value Rni should be assigned depending on the test results of brick (stone) masonry in the construction area and indicated in the project.
If it is impossible to obtain the value at the construction site Rnt equal to or exceeding 120 kPa (1.2 kgf/cm 2), the use of brick or stone masonry for the construction of load-bearing and self-supporting walls is not allowed.
When constructing buildings in seismic areas, control tests should be carried out to determine the actual value of the normal adhesion of the masonry. Construction
buildings with load-bearing and self-supporting brick (stone) walls are not allowed without carrying out control tests of the masonry.
In the levels of floors and coverings of brick buildings, anti-seismic belts made of monolithic reinforced concrete with continuous reinforcement should be installed along all longitudinal and transverse load-bearing walls.
In buildings with monolithic reinforced concrete floors embedded along the contour into the walls, it is allowed not to install anti-seismic belts at the floor level. In this case, the length of the part of monolithic reinforced concrete floors and coverings resting on brick walls must be at least 250 mm.
Anti-seismic belts and monolithic reinforced concrete floors of the upper floor of the building must be connected to the masonry by vertical outlets of reinforcement or reinforced concrete
connections.
The anti-seismic belt must have a zone for supporting the ceiling and be installed across the entire width of the wall. In external walls with a thickness of 510 mm or more, the width of the belt can be less than the thickness of the wall by up to 150 mm. The height of the belt must be at least 150 mm, concrete class not lower than B12.5. Anti-seismic belts are reinforced with spatial frames with longitudinal reinforcement of at least 4Ø10 for seismicity of construction sites of 7 and 8 points and at least 4Ø12 for seismicity of construction sites of 9 and 10 points.
At the junctions of load-bearing walls, reinforcing meshes with a total cross-sectional area of longitudinal reinforcement of at least 1 cm 2 and a length of at least 150 cm must be placed in the masonry every 700 mm in height if the seismicity of the construction site is 7 and 8 points and after 500 mm if the seismicity of the construction sites is 9 and 10 points.
The internal reinforced concrete layer of three-layer monolithic masonry must be made of concrete of class not lower than B10 and have a thickness of at least 100 mm.
The outer layers of monolithic masonry (brick) must be connected to each other by horizontal reinforcement, installed in increments of no more than 600 mm and passed through the inner layer of concrete.
Floors and coverings must rest on the internal reinforced concrete layer of monolithic masonry or on an anti-seismic belt.
The height of the floor of buildings with load-bearing walls made of brickwork, not reinforced with reinforcement or reinforced only with horizontal reinforcing mesh, should not exceed 5.0 for seismicity of 7, 8 and 9 points, respectively; 4.0 and 3.5 m. In this case, the ratio of floor height to
The wall thickness should be no more than 12.
The height of the floor of buildings with walls of a complex structure or of monolithic masonry can be taken with seismicity of 7, 8, 9 and 10 points, respectively 6.0; 5.0; 4.5 and 4.0 m.
In buildings with load-bearing brick walls, in addition to external longitudinal walls, as a rule, there must be at least one internal longitudinal wall connected to the end external and internal transverse walls. The transverse load-bearing walls of staircases must extend across the entire width of the building.
The distances between the axes of transverse walls or frames replacing them must be checked by calculation and be no more than the values given in the table. 7.4 SNiP RK 2.03-30-2006.
The dimensions of brick wall elements should be determined by calculation. For brickwork without reinforcement or with reinforcement in the form of horizontal reinforcement in the joints, the requirements given in Table 1 must also be met. 7.5 SNiP RK 2.03-30-2006.
Door and window openings in the brick walls of staircases with seismicity of 8 points or more must have reinforced concrete frames.
Stair landings and stair landing beams should be embedded in the masonry to a depth of at least 250 mm and anchored. Elements of prefabricated stairs (steps, stringers, prefabricated flights) must be secured.
The installation of cantilever steps embedded in the masonry of staircase walls is not allowed
The extension of balconies in buildings with stone walls and prefabricated floors should not exceed 1.5 m.
Sections of walls and pillars above the attic floor, having a height of more than 400 mm, must be reinforced or reinforced with monolithic reinforced concrete inclusions anchored in an anti-seismic belt.
Lintels should, as a rule, be installed over the entire thickness of the wall and embedded in the masonry to a depth of at least 350 mm. With opening width before 1.5 m sealing of jumpers is allowed
by 250 mm.
In seismic areas, the use of prefabricated timber lintels is not allowed.
Load-bearing walls housing ventilation ducts and chimneys should be designed as a complex structure.
Within the plan of a building or compartment, it is not allowed to change the direction of layout of reinforced concrete slabs of prefabricated floors (coverings) made in accordance with paragraphs 7.23.a, b of SNiP RK 2.03-30-2006.
Self-supporting walls must have connections with the frame that do not prevent horizontal displacements of the frame along the walls. A gap of at least 20 mm must be provided between the surface of the walls and the columns of the frame.
Along the entire length of a self-supporting wall made of brick (stone) masonry, at the level of floor slabs (coverings) or the top of window openings, anti-seismic belts must be installed, connected by flexible connections to the building frame. At the intersection of end and longitudinal walls, anti-seismic joints should be installed along the entire height of the walls.
The strength of self-supporting wall structures and their fastenings should be checked by calculation performed in accordance with clause 5.21. Seismic forces acting in the plane of self-supporting walls must be absorbed by the walls themselves.
Lecture topic 21. Basic principles of earthquake resistance design for masonry buildings (continuation of lecture topic 20)
Lecture outline
· Complex designs. The rule for horizontal and vertical reinforcement of complex structures.
· Features of calculation of complex structures.
Lecture abstracts
1. Methods for increasing the seismic resistance of brick (stone) walls. Standard requirements for the installation of vertical reinforced concrete cores in blank walls, as well as in walls with openings. Requirement of standards for strengthening load-bearing walls in which ventilation ducts and chimneys are located.
Main content of the lecture
The seismic resistance of brick (stone) walls of buildings should be increased:
· mesh made of reinforcement, laid in horizontal joints of the masonry;
· creating a complex structure by reinforcing walls with vertical meshes of reinforcement in a layer of shotcrete of a class not lower than B7.5 or in a layer of cement-sand mortar of a grade not lower than 100;
· creating a complex structure by including monolithic vertical and horizontal reinforced concrete elements into the masonry;
· installation of an internal reinforced concrete layer in the masonry (three-layer monolithic masonry).
To increase the seismic resistance of brick walls, it is allowed to use other experimentally proven methods.
When designing complex structures in the form of walls reinforced with mesh reinforcement in a layer of shotcrete or in a layer of cement-sand mortar:
grids are usually installed on both sides of the walls;
The thickness of the layers of concrete or mortar must be at least 40 mm on each side of the wall;
The reinforcement mesh is fastened to the walls using reinforcement anchors with a diameter of at least 6 mm, which are installed in a checkerboard pattern with a pitch of no more than 600 mm.
When reinforcing walls using this method, technological measures should be taken to ensure reliable adhesion of layers of concrete or mortar to the masonry.
Reinforced concrete inclusions in masonry of a complex structure must be open on at least one side.
Vertical reinforced concrete inclusions (cores) must be connected to anti-seismic belts. Horizontal reinforcement of walls and anti-seismic belts should be passed through vertical reinforced concrete inclusions.
Cores should be installed at the junctions of walls, at the edges of windows and doors
openings, on blind sections of walls with a step not exceeding the height of the floor. Concrete cores must be at least class B15.
Lecture 22
Lecture topic 22. Principles of ensuring seismic resistance of one-story industrial buildings made of reinforced concrete prefabricated structures
Lecture outline
· Load-bearing structures of one-story industrial buildings. Reinforced concrete prefabricated structures.
· One-story industrial buildings not equipped with overhead cranes. Measures to ensure seismic resistance of one-story industrial buildings not equipped with overhead cranes.
· One-story industrial buildings equipped with overhead cranes. Measures to ensure seismic resistance of one-story industrial buildings.
Lecture abstracts
1. Structural diagrams of one-story industrial buildings. Structural diagrams of a building in the form of a transverse frame of racks, clamped in the foundations and hinged to the roof crossbars.
2. Vertical connections along columns in one-story industrial buildings equipped with overhead cranes. The use of prefabricated reinforced concrete rafter and sub-rafter structures in buildings with a calculated seismicity of 7, 8 and 9 points.
3. Providing hard drive cover for the building with precast concrete cover structures. Requirements of earthquake-resistant construction standards.
Main content of the lecture
Lecture 23.
Lecture topic 23. Principles of ensuring seismic resistance of one-story industrial buildings made of reinforced concrete prefabricated structures (continued)
Lecture outline
· Coverings of frame buildings.
· Walls in frame buildings.
· Requirements for earthquake-resistant construction.
Lecture abstracts
1. Structural schemes of frame one-story buildings: combined, in which a frame scheme is adopted in one direction of the building, and a braced one in the other; in the form of racks, pinched in the foundations and hingedly connected to the rafter structures; in the form of spatial frame structures hingedly connected to the foundations.
2. Conditions for ensuring separate operation of load-bearing and non-load-bearing structures (except for hanging systems). Conditions for ensuring separate operation of load-bearing structures and hanging systems.
3. Conditions for ensuring the rigidity of the disk coating of an industrial building using prefabricated reinforced concrete slabs.
Main content of the lecture
Lecture 24.
Lecture topic 24. Principles for ensuring seismic resistance of multi-storey large-panel buildings
Lecture outline
· Large-panel structures of multi-storey buildings.
· Ceilings and coverings of large-panel buildings.
· Walls in large-panel buildings.
· General principles of design of large-panel buildings.
Lecture abstracts
1. Principles of ensuring seismic resistance of inter-storey large-panel buildings. Structural and planning cell in large-panel buildings depending on the pitch of the transverse walls.
2. Connections of wall and ceiling panels. Requirements for the class of concrete for embedding joints of wall and ceiling panels. Standard requirements for the intended thickness of single-layer wall panels and the thickness of the internal load-bearing layer of multi-layer panels.
3. Reinforcement of wall panels. Structural requirements for reinforcement of wall panels. Vertical reinforcement along the contour of window and door openings. A structural requirement of standards for the purpose of the cross-sectional area of vertical reinforcement installed at the edges of window and door openings.
Main content of the lecture
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