at 375 N/mm

b) the maximum in the extreme rows in the absence of bordering corners in tension and compression

c) the maximum in the middle rows, as well as in the outer rows in the presence of bordering corners:

in tension

under compression

2 Distance from the center of the bolt hole to the edge of the element

a) minimum along effort:

at 375 N/mm

at 375 N/mm

b) the same, across the effort:

with cut edges

with rolling edges

c) maximum

d) minimum in friction connection at any edge and any direction of force

3 Minimum distance between hole centers along force for staggered bolts

Designations adopted in table 40:

Bolt hole diameter;

The thickness of the thinnest outer element;

The distance across the force between rows of holes.

Notes

1 The diameter of the holes should be taken: for bolts of accuracy class A; for bolts of accuracy class B in the structures of supports VL, switchgear and KS mm, in other cases

(1; 2 or 3 mm), where is the diameter of the bolt.

2 In single-bolt connections of lattice elements (braces and spacers), except for those constantly working in tension, with a thickness of elements up to 6 mm made of steel with a yield strength of up to

375 N/mm distance from the edge of the element to the center of the hole along the force is allowed

take 1.35 (without tolerance in the manufacture of elements in the direction of reduction, which should be indicated in the project).

3 When placing the bolts in a checkerboard pattern at a distance not less than specified in pos.3,

the section of the element should be determined taking into account its weakening by holes located in one section across the force (not along a zigzag).

When attaching a corner with one shelf with bolts placed in a checkerboard pattern, the hole farthest from its end should be placed at the risk closest to the butt.

It is allowed to fasten the elements with one bolt.

14.2.3 Bolts of accuracy class A should be used for joints in which holes are drilled to the design diameter in collected elements, or along the conductors in individual elements and parts, or drilled or pressed to a smaller diameter in individual parts, followed by reaming to the design diameter in the assembled elements.

Bolts of accuracy class B in multi-bolt connections should be used for steel structures with a yield strength of up to 375 N/mm.

In connections where bolts work mainly in tension, as a rule, bolts of accuracy classes B or high strength should be used.

14.2.4 Bolts having sections with different diameters along the length of the uncut part should not be used in joints in which these bolts work in shear.

14.2.5 Shear bolt threads in structural members, power line pylons and exposed switchgears, as well as in connections with an outer element thickness of up to 8 mm, must be outside the package of connected elements; in other cases, the bolt thread should not go deeper into the hole by more than half the thickness of the extreme element on the side of the nut or more than 5 mm.

14.2.6 Installation of washers on bolts should be carried out in accordance with the requirements SNiP 3.03.01.

In design connections with bolts of accuracy classes A and B (with the exception of fastening auxiliary structures) it is necessary to provide measures against self-unscrewing of nuts (setting spring washers, second nuts, etc.).

14.2.7 On the beveled surfaces of the parts and elements to be joined (the inner edges of the flanges of I-beams and channels), oblique washers should be installed under the heads of bolts or nuts.

14.2.8 The diameter of the hole for bolts in rolled elements must correspond to GOST 24839 and note 1 of table 40.

14.2.9 The design force that can be taken by one bolt, depending on the type of stress state, should be determined by the formulas:

at cut

when crushed
in tension

where , , - design resistance of single-bolt connections;

And - the cross-sectional areas of the bolt shaft gross and net threaded parts, respectively, taken in accordance with Table D.9 of Appendix D;

The number of calculated sections of one bolt;

Bolt shank outer diameter;

The smallest total thickness of the connected elements, crushed in one direction;

Coefficient of working conditions, determined according to table 1;

Working conditions coefficient bolted connection, determined according to table 41 and taken no more than 1.0.

Table 41

Characteristic			Values		Meaning
		fluidity			coefficient
		connected
		elements, N/mm
bolted	tense
connections	states
Single bolt, bolt
accuracy classes A,
high strength
		St. 285 to 375
multi-bolt,
class bolts
accuracy A
		St. 285 to 375

Designations adopted in table 41:

Distance along the force from the edge of the element to the center of the nearest hole;

Distance along the force between the centers of the holes;

Bolt hole diameter.

Notes:

1 For calculation of a multi-bolt connection for shear and collapse with bolts of accuracy class B, as well as with high-strength bolts without adjustable tension at all values ​​of the limit

the yield strength of the steel of the elements to be joined, the values ​​of the coefficient should be multiplied by

2 To calculate a multi-bolt joint for collapse, it is necessary to take the value of , which is the smaller of those calculated with the accepted values ​​of , , .

14.2.10 When a bolted joint is subjected to a force passing through the center of gravity of the joint, the distribution of this force between the bolts should be assumed to be uniform. In this case, the number of bolts in the connection should be determined by the formula

where is the smallest of the values ​​or , or the value calculated according to the requirements of 14.2.9.

In cases where in the joint the distance between the extreme bolts along the shear force exceeds 16, the value in formula (189) should be increased by dividing by

coefficient , taken equal to at least 0.75. This requirement does not apply when a force is applied along the entire length of the connection (for example, in a girder connection of a beam).

14.2.11 When a bolted joint is acted upon by a moment that causes shear of the connected elements, the distribution of forces on the bolts should be taken in proportion to the distances from the center of gravity of the joint to the bolt in question.

The force in the most loaded bolt shall not exceed the smaller of the values ​​or calculated in accordance with the requirements of 14.2.9.

14.2.12 When a bolted joint is simultaneously subjected to a force and a moment acting in the same plane and causing a shift of the connected elements, the bolts should be checked for the resultant force (in the most loaded bolt, which should not exceed

the smaller of the values ​​or calculated according to the requirements of 14.2.9).

14.2.13 With simultaneous action on the bolted connection of forces that cause shear and tension of the bolts, the most stressed bolt, along with the check according to the formula (188), should be checked according to the formula

where and are the forces acting on the bolt, shearing and tensile, respectively;

Design forces determined in accordance with the requirements of 14.2.9.

14.2.14 In fastenings of one element to another through spacers or other intermediate elements, as well as in elements with a one-sided lining, the number of bolts should be increased by 10% in comparison with the calculation.

When fastening protruding shelves of corners or channels using short pieces, the number of bolts attaching the short piece to this shelf should be increased by 50% compared to the calculation result.

14.2.15 Foundation (anchor) bolts should be checked in accordance with the requirements of SNiP

2.09.03 .

14.3 Friction connections (bolts with controlled tension)

14.3.1 Friction joints, in which forces are transmitted through friction that occurs on the contact surfaces of the elements to be joined due to the tension of high-strength bolts, should be used:

in steel structures with a yield strength over 375 N/mm and directly perceiving moving, vibrational and other dynamic loads;

in multi-bolt connections, which are subject to increased requirements in terms of limiting deformation.

14.3.2 Bolts, nuts and washers shall be used in friction joints in accordance with the requirements of 5.6.

Bolts should be placed according to the requirements of table 40.

14.3.3 The design force that can be taken by each friction plane of elements tightened by one high-strength bolt should be determined by the formula

where is the calculated tensile strength high strength bolt, determined according to the requirements of 6.7;

The cross-sectional area of ​​the bolt on the thread, taken in accordance with Table D.9 of Appendix D;

Friction coefficient taken according to table 42;

Coefficient taken according to table 42.

Table 42

	Method of processing (cleaning)	Coefficient	Coefficient	with tension control
	surfaces to be joined
			bolts according to the torque with a difference
			nominal diameters of holes and bolts,
			mm, under load
			dynamic		dynamic
			static		static
	1 Shot blast or
	shot blasting two
	surfaces without
	conservation
	2 Flame two
	surfaces without
	conservation
	3 steel brushes two
	surfaces without
	conservation
	4 No processing

Note - When checking the tension of the bolts by the angle of rotation of the nut, the values ​​\u200b\u200bshould be multiplied by 0.9.

14.3.4 When a frictional joint is subjected to a force , which causes a shift of the connected elements and passes through the center of gravity of the joint, the distribution of this force between the bolts should be assumed to be uniform. In this case, the number of bolts in the connection should be determined by the formula

where is the design force determined by the formula (191);

Number of friction planes of connected elements;

Coefficient of working conditions, taken according to table 1;

Coefficient of operating conditions of a friction joint, depending on the number of bolts required to absorb the design force, and taken equal to:

14.3.5 When a friction joint is subjected to a moment or a force and a moment that cause a shift of the connected elements, the distribution of forces between the bolts should be taken in accordance with the instructions in 14.2.11 and 14.2.12.

14.3.6 When acting on a friction joint, in addition to the force, causing shear of the connected elements, force causing tension in the bolts, the value of the coefficient , determined according to the requirements of 14.3.4, should be multiplied by the coefficient , where is the tensile force per one bolt, is the bolt tension force, taken equal to .

14.3.7 The diameter of the bolt in the friction joint should be taken under the condition,

where - the total thickness of the connected elements, crushed in one direction, - the diameter of the bolt.

In friction joints with large quantity bolts, their diameter should be as large as possible.

14.3.8 The design must specify steel grades and mechanical properties bolts, nuts and washers and the standards to which they must be supplied, the way in which the connected

surfaces, axial force , taken in accordance with 14.3.6.

14.3.9 When designing friction joints, it should be possible to have free access for installing bolts, tightly tightening the package with bolts and tightening nuts using torque wrenches, wrenches, etc.

14.3.10 For high strength bolts GOST R 52644 with enlarged heads and nuts

and when the difference between the nominal diameters of the hole and the bolt is not more than 3 mm, and in structures made of

steel with a temporary resistance of at least 440 N / mm - no more than 4 mm, it is allowed to install one washer under the nut.

14.3.11 The strength calculation of the elements to be joined, weakened by holes in the friction joint, should be carried out taking into account the fact that half of the force applied to each bolt is transferred by friction forces. In this case, the verification of weakened sections should be carried out: with moving, vibrational and other dynamic loads - by the cross-sectional area

net ; under static loads - by the gross sectional area (at ) or by the nominal area (at ).

14.4 Belt connections in composite beams

14.4.1 Welded and friction belt joints of a composite I-beam should be calculated using the formulas in Table 43.

Table 43

Character	Belt connections	Formulas for calculating belt connections in
loads		composite beams
motionless

Friction

Movable

Welded (double-sided seams)

Friction

Designations adopted in table 43:

The shearing chord force per unit length caused by the transverse force (here is the static gross moment of the beam chord about the central axis);

Number of fillet welds: for double-sided welds 2, for single-sided 1;

Quantities determined according to 14.3.3, 14.3.4;

Pressure from a concentrated load per unit length, determined taking into account the requirements of 8.2.2 and 8.3.3 (for fixed loads 1);

And - reliability factors for the load, taken according to SP 20.13330;

Belt bolt pitch;

The coefficient taken equal to: 0.4 with a load along the upper chord of the beam, to which the web is attached, and 1.0 if there is no attachment of the web or with a load along the lower chord.

In the absence of transverse stiffeners for the transfer of fixed concentrated loads applied to the upper chord, as well as when a fixed concentrated load is applied to the lower chord, regardless of the presence of stiffeners at the places of load application, the belt connections should be calculated as for a moving load.

Welds made with penetration through the entire thickness of the wall should be considered equal strength with the wall.

14.4.2 In beams with friction belt connections with multi-sheet belt packages, the attachment of each of the sheets behind the place of its theoretical break should be calculated for half the force that can be perceived by the section of the sheet. The attachment of each sheet in the area between the actual place of its break and the place of break of the previous sheet should be calculated on the total force that can be perceived by the section of the sheet.

15 Additional requirements for the design of certain types of buildings, structures and structures

15.1 Distances between expansion joints

Distances between expansion joints of steel frames one-story buildings and structures should not exceed highest values taken according to table 44.

Table 44

buildings and structures	directions
heated		along the block
	temperature	building length)
		by block width
unheated		along the block
building and hot	temperature	building length)
		by block width
	from the expansion joint or the end of the building
	to the axis of the nearest vertical connection
open overpass	between expansion joints along
	from the expansion joint or the end of the building
	to the axis of the nearest vertical connection

Note - If there are two vertical connections between the expansion joints of a building or structure, the distance between the latter in the axes should not exceed: for buildings 40-50 m and for open flyovers 25-30 m, while for buildings and structures erected at design temperatures of -45 °C, the smaller of the specified distances should be taken.

If the distances indicated in Table 44 are exceeded by more than 5%, as well as if the frame rigidity is increased by walls or other structures, the calculation should take into account climatic temperature effects, inelastic deformations of structures and compliance of nodes.

15.2 Trusses and structural slabs

15.2.1 The axes of the bars of trusses and structures should, as a rule, be centered at all nodes. The centering of the rods should be carried out in welded trusses according to the centers of gravity of the sections (rounded up to 5 mm), and in bolted trusses - according to the risks of the corners closest to the butt.

The displacement of the axes of the chords of trusses when changing the sections may not be taken into account if it does not exceed 1.5% of the height of the chord of a smaller section.

In the presence of eccentricities at the nodes, the elements of trusses and structures should be calculated taking into account the corresponding bending moments.

When loads are applied outside the truss nodes, the chords must be designed for the combined action of longitudinal forces and bending moments.

15.2.2 When calculating flat trusses, the connections of elements in truss nodes can be taken as hinged:

at sections of elements from corners or tees;

with I-beam, H-shaped and tubular sections of elements, when the height ratio

section to the length of the element between the nodes does not exceed: 1/15 - for structures operated in areas with design temperatures below minus 45 ° C; 1/10 - for structures operated in other areas.

If the specified ratios are exceeded, additional bending moments in the elements due to the rigidity of the nodes should be taken into account.

15.2.3 The distance between the edges of the elements of the lattice and the belt in the nodes of welded trusses with gussets should be taken not less than (6-20) mm, but not more than 80 mm (here - thickness of the gusset, mm).

A gap of at least 50 mm should be left between the ends of the joined elements of the truss belts, overlapped by overlays.

Flange welds attaching the elements of the truss lattice to the gussets should be brought to the end of the element for a length of at least 20 mm.

15.2.4 In truss nodes with belts made of T-beams, I-beams and single corners, fastening of gussets to the shelves of the belts end-to-end should be carried out with penetration through the entire thickness of the gusset. In structures of group 1, as well as those operated in areas at design temperatures below minus 45 ° C, the junction of nodal gussets to the belts should be carried out in accordance with Appendix K (Table K.1, position 7).

15.2.5 When calculating truss nodes with tubular and I-section rods and attaching lattice elements directly to the belt (without gussets), the bearing capacity should be checked:

belt walls at local bending (punching) at the junction of lattice elements (for round and rectangular pipes);

the side wall of the belt at the junction of the compressed element of the lattice (for rectangular pipes);

belt shelves for bending (for an I-section);

belt walls (for I-section);

lattice elements in the section adjacent to the belt;

welds attaching the elements of the lattice to the belt.

These checks are given in Appendix L.

In addition, the Z-properties requirements for truss chord materials should be observed (see 13.5).

15.2.6 When roof truss spans exceed 36 m, a construction lift equal to the deflection from constant and long-term standard loads should be provided. At flat roofs construction lifting should be provided regardless of the span, taking it equal to the deflection from the total standard load plus 1/200 of the span.

15.3 Columns

15.3.1 The sending elements of through columns with gratings in two planes should be reinforced with diaphragms located at the ends of the sending element.

In through columns with a connecting grid in the same plane, the diaphragms should be located at least 4 m apart.

15.3.2 In columns and posts with one-sided girdle seams according to 14.1.9, in the attachment points of braces, beams, spacers and other elements in the force transfer zone, two-sided girdle seams should be used that extend beyond the contours of the attached element (node) by a length of 30

From each side.

15.3.3 Fillet welds attaching the gussets of the connecting grid to the overlapping columns should be assigned according to the calculation and placed on both sides of the gusset along the column in the form of separate sections in a checkerboard pattern; at the same time, the distance between the ends of such seams should not exceed the thickness of the gusset by 15 times.

In structures erected in areas with design temperatures below minus 45 ° C, as well as when using manual arc welding fillet welds must be continuous along the entire length of the gusset.

15.3.4 Assembly joints of columns should be made with milled butt-welded ends, on plates with welded seams or bolted joints, including friction ones. When welding overlays, welds should not be brought to the joint by 25 mm on each side. It is allowed to use flange connections with the transfer of compressive forces through a tight touch, and tensile ones - by bolts.

15.3.5 In through columns, the branches of which are connected by planks, the following should be taken:

the width of the intermediate slats - equal to from 0.5 to 0.15 (here - the overall width of the column in the plane of the slats);

the width of the end strips - equal to from 1.3 to 1.7.

15.4 Links

15.4.1 In each temperature block of the building, it is necessary to provide independent system connections.

15.4.2 Bottom chords of beams and trusses crane tracks spans over 12 m should be reinforced with horizontal braces.

15.4.3 Vertical connections between the main columnsbelow the level of the crane runway beams, it should be located, if possible, in the middle or near the middle of the temperature block; it is expedient to place the upper vertical ties along the ends of the building and in the steps of the columns adjacent to the expansion joints, as well as in those steps where the ties of the lower tier are located.

In case of insufficient rigidity of the branches of the columns in the longitudinal direction of the building, it is allowed to install additional spacers fixed in the junctions.

With two-branch columns, vertical connections should be placed in the plane of each of the branches of the column. The branches of two-branch connections, as a rule, should be interconnected by connecting grids.

15.4.4 Coating link system depends on the type of frame (steel or mixed), the type of coating (purlin or non-purlin), the load capacity of the cranes and their mode of operation, the presence of overhead handling equipment and under roof trusses.

15.4.5 At the level of the lower belts roof trusses, transverse horizontal ties should be provided in each span of the building at the ends, as well as at expansion joints building.

With a temperature block length of more than 144 m and with cranes with a large lifting capacity (50 t), intermediate horizontal transverse braces should also be provided approximately every 60 m.

AT buildings with a steel frame, equipped with overhead cranes with a lifting capacity of 10 tons

and more, and in buildings with truss trusses, longitudinal braces should be provided, located along the extreme panels of the lower chords of truss trusses and forming, together with transverse braces, a rigid contour in the plane of the lower truss chords.

AT in single-span buildings of this type, longitudinal connections along the lower chords should be assigned along both rows of columns.

AT multi-span buildings with cranes with a lifting capacity 50 t, with an operating mode of 1K-6K (in accordance with SP 20.13330), as a rule, longitudinal ties should be located along the outermost columns and in one row along the middle columns. In multi-span buildings with cranes with a lifting capacity of 50 tons, with an operating mode of 7K-8K, as well as in buildings with height differences, a more frequent arrangement of longitudinal ties along the lower chords of trusses should be assigned. Longitudinal ties along the middle rows of columns with the same height of adjacent spans should be designed the same as along the outermost rows of columns.

AT if the flexibility in the horizontal plane of the panels of the lower chords of trusses (see 10.4), located between two transverse truss trusses, is insufficient, then it must be ensured by placing guys attached to the nodes of truss trusses.

15.4.6 On the upper belts roof trusses transverse horizontal ties when covering

with runs should be assigned in any one-story industrial building. It is recommended to combine transverse braced trusses along the upper and lower chords in the plan.

The upper chords of the truss trusses, which are not directly adjacent to the cross braces, should be braced in the plane of these braces.

15.4.7 If available hard drive roofs at the level of the upper chords in coverings without purlins (in which large-sized reinforced concrete slabs welded to the upper chords or a profiled sheet is attached in each corrugation), cross-braces along the upper chords of the trusses should be arranged only at the ends of the building and at expansion joints. In the remaining steps, spacers are needed at the ridge and at the supports of the truss trusses.

What are the reasons for assigning the distance between the bolts (minimum or maximum).

Bolts (including high-strength ones) should be placed in accordance with Table. 39.

Table 39

#G0Distance characteristic	Bolt spacing
1. Distances between bolt centers in any direction: a) minimum	2,5
b) the maximum in the extreme rows in the absence of bordering corners in tension and compression	8 or 12
c) the maximum in the middle rows, as well as in the outer rows in the presence of bordering corners:
in tension	16 or 24
under compression	12 or 18
2. Distances from the center of the bolt to the edge of the element:
a) minimum along effort	2
b) the same, across the effort:
with cut edges	1,5
with rolling edges	1,2
c) maximum	4 or 8
d) minimum for high-strength bolts with any edge and any direction of force	1,3
* In connected elements made of steel with a yield strength of more than 380 MPa (3900 kgf / sq. cm) minimum distance between bolts should be taken equal to 3. The designations adopted in Table. 39: - bolt hole diameter; is the thickness of the thinnest outer element. Note. In connected elements made of steel with a yield strength of up to 380 MPa (3900 kgf / sq. cm), it is allowed to reduce the distance from the center of the bolt to the edge of the element along the force and the minimum distance between the centers of the bolts in cases of calculation taking into account the relevant coefficients of the operating conditions of the joints in accordance with paragraphs. 11.7* and 15.14*

Connecting bolts should be placed, as a rule, at maximum distances; at joints and nodes, bolts should be placed at minimum distances.

When placing bolts in a checkerboard pattern, the distance between their centers along the force should be taken at least 1.5 where is the distance between rows across the force, is the diameter of the bolt hole. With this arrangement, the section of the element is determined taking into account its weakening by holes located only in one section across the force (not along the "zigzag").

When attaching a corner with one shelf, the hole farthest from its end should be placed at the risk closest to the butt.

2.28 Calculation of bolts in a joint working on axial force(give the calculated dependence with an explanation of the quantities included in it).

If the external force acting on the connection is directed parallel to the longitudinal axis of the bolts, then they will work in tension. In the static operation of such a connection, the quality of the holes and the surface of the bolt does not play any role, and bolts of normal and increased accuracy work in tension in the same way (their design resistances are equal).

It is interesting to note that the initial tensions of the bolts do not affect their tensile strength. This is explained by the fact that the initial stresses are internal stresses, balanced by the compression forces between the connected elements. Applying external forces N to the connected elements, we will gradually replace them with the compression forces between the elements, without disturbing the balance of the bolt - element. In this case, the tightness of the connection will not be violated. Then, when the external forces N begin to exceed the internal initial bolt tightening forces, the solidity of the connection will be broken and the tensile force in the bolt will begin to increase. Thus, the strength of the connection is determined by the tensile strength of the material of the bolts, regardless of the forces of the initial tension of the bolt.

Table 8

Methods for processing the surfaces to be joined	friction coefficient,	Coefficient,
Sand blasting or shot blasting two surfaces	0,38	1,02
The same, with preservation by metallization with zinc or aluminum	0,50	1,02
Sandblasting or shot blasting of one surface with its conservation epoxy glue with corundum powder, the other surface is cleaned with steel brushes, without preservative	0,50	1,02
Flame two surfaces	0,42	1,02
Steel brushes two surfaces	0,35	1,06
No processing	0,25	1,20

In tension joints, bolts from the same steels are used as for shear joints, and for foundation bolts - in table. 9. In these connections, the forces on the bolts are often applied with eccentricity, which causes their design resistances to be reduced.

In foundation bolts, the decrease in the design resistance of the bolt material against the nominal value is also explained by the fact that the degree of tension of adjacent bolts of the column base during the installation of the column can be different, and therefore, in reality, some overload of individual bolts is possible. The force that can be taken by one bolt is determined by the formula:

Similar to formula (6.2) required amount bolts in a joint working on the action of a centrally applied tensile force, determine:

With the simultaneous action of forces that shear and stretch the joint, its strength is checked separately for shear according to formulas (6.1) - (6.2), and for tension according to formulas (6.5) and (6.5).

The calculation of foundation bolts does not differ from the calculation of ordinary bolts and is carried out according to formulas (6.4) and (6.5), however, for proper fixing of the bolt in the foundation (determining the length of its embedding in concrete), it is necessary to additionally check it for tearing out of the foundation.

Elements in the node can be fixed with one bolt.
Bolts having sections with different diameters along the length of the uncut part are not allowed to be used in joints in which these bolts work in shear.
Under the nuts of the bolts, round washers should be installed in accordance with GOST 11371-78 *. Each bolt is installed in connection with two round washers(one is placed under the head of the bolt, the other under the nut). (See Recommendations and standards for the technology of setting bolts in field joints of metal structures, clause 7.8).

Hole formation

Holes should be formed by punching or drilling (See SP53-101-98 "Manufacturing and quality control of steel building structures, clause 8.2").

Holes in the flanges should be made by drilling (See Recommendations for the calculation, design, manufacture and installation of flanged joints of steel building structures, clause 6.6).

The formation of holes in the calculated connections working for shear and crushing with bolts of strength classes 5.8, 8.8, 10.9 should be provided by drilling in conductors. Hole punching is allowed in off-design joints (See Recommendations and standards on the technology of setting bolts in field joints of metal structures, pages 18-19).

Bolt hole diameter

The diameter of the drilled holes must not exceed the diameter of the bolt by more than 3mm. (See Recommendations and standards for the technology of setting bolts in field joints of metal structures, clause 7.6)

Securing bolts from loosening

Solutions to prevent self-loosening of nuts - setting spring washers (GOST 6402), locknuts or other methods of securing nuts from self-loosening - must be indicated in the working drawings of the KM brand. Application of spring washers not allowed with oval holes, with a difference in the nominal diameters of the hole and the bolt of more than 3 mm, when installed together with a round washer (GOST 11371), as well as in bolted connections working in tension. It is forbidden to lock the nuts by driving the bolt threads or by welding the nuts to the bolt shank. (See SP70.13330-2012 p.4.5.5)

Nuts of high-strength bolts and bolts of strength class 10.9, tightened to a force of more than 50 percent of the design tensile strength, are not additionally secured. Bolt nuts without controlled tension are secured with split washers or locknuts. Only locknuts are installed in bolted connections in tension. The installation of spring washers is not recommended. (See Recommendations and standards for the technology of setting bolts in field joints of metal structures, clause 7.9)

The thread of the shear bolt should not be more than half the thickness of the element adjacent to the nut, or more than 5 mm, except for structural structures, power transmission towers and open switchgear and transport contact lines, where the thread must be outside the package of connected elements. (See SNiP II-23-81* p.12.18)

The protruding part of the bolt above the nut

The lengths of bolts in friction and flange connections are assigned depending on the total thickness of the parts to be assembled. In this case, the thread protruding beyond the nut must have at least one turn with a full profile. In connections without controlled tension of bolts working on shear and collapse, the length of the bolts is selected in such a way that the thread would be at least 5 mm away from the nearest shear plane. (See Recommendations and standards for the technology of setting bolts in field joints of metal structures, p. 7.16).

Nuts and heads of bolts, including foundation bolts, after tightening, should be in close contact (without gaps) with the planes of washers or structural elements, and the bolt threads should protrude from the nuts by at least one turn with a full profile. (SP70.13330 p.4.5. 7).

Bolts (including high-strength ones) should be placed in accordance with Table. 39.

Distance characteristic	Bolt spacing
1. Distances between bolt centers in any direction:
a) minimum
b) the maximum in the extreme rows in the absence of bordering corners in tension and compression	8d or 12 t
c) the maximum in the middle rows, as well as in the outer rows in the presence of bordering corners:
in tension	16d or 24 t
	12d or 18 t
2. Distances from the center of the bolt to the edge of the element:
a) minimum along effort
b) the same, across the effort:
with cut edges
« rolling
c) maximum	4d or 8 t
d) minimum for high-strength bolts with any edge and any direction of force

* In joined elements made of steel C235, C245, and C255, the minimum distance between the bolts should be taken equal to 3d.
The designations adopted in Table. 39:
d - bolt hole diameter;
t is the thickness of the thinnest outer element.
Connecting bolts should be placed, as a rule, at maximum distances; at joints and nodes, bolts should be placed at minimum distances.
When placing bolts in a checkerboard pattern, the distance between their centers along the force should be taken at least a + 1.5d, where a is the distance between rows across the force, d is the diameter of the bolt hole. With this placement, the section of the element An is determined taking into account its weakening by holes located only in one section across the force (not along the “zigzag”).
When attaching a corner with one shelf, the hole farthest from its end should be placed at the risk closest to the butt.

CJSC "TsNIIPSK im. Melnikov
OAO NIPI Promstalkonstruktsiya
ORGANIZATION STANDARD

Steel building structures

BOLT CONNECTIONS

Design and calculation

STO 0041-2004

(02494680, 01408401)

Moscow 2004

Ccontent

Foreword

1 DEVELOPED CJSC Central Order of the Red Banner of Labor Research and Design Institute of Building Metal Structures. Melnikova (CJSC "TsNIIPSK named after Melnikov")

OJSC Research and Design Institute "Promstalkonstruktsiya"

2 INTRODUCED by the organizations developing the Standard

3 ADOPTED at the Scientific and Technical Council TsNIIPSK them. Melnikov dated November 25, 2004 with the participation of representatives of the organization that developed the Standard

4 INTRODUCED for the first time

5 REVISION November 2005

6 Development, approval, approval, publication (replication), updating (change or revision) and cancellation of this standard are carried out by developing organizations

Introduction

This standard was developed in accordance with the Federal Law "On Technical Regulation" No. 184-FZ and is intended for use by all departments of ZAO TsNIIPSK im. Melnikov" and OAO NIPI "Promstalkonstruktsiya", specializing in the development of KM and KMD projects, diagnostics, repair and reconstruction industrial buildings and structures for various purposes.

The standard can be applied by other organizations if these organizations have certificates of conformity issued by the Certification Bodies in the voluntary certification system created by the standard development organizations.

Organizations-developers do not bear any responsibility for the use of this standard by organizations that do not have certificates of conformity.

The need to develop a standard is dictated by the fact that the experience gained by the organizations developing the standard, as well as domestic enterprises and organizations in the field of design, manufacture and implementation of steel structures with bolted field connections, is contained in various regulatory documents, recommendations, departmental rules and others, in part obsolete and not generally covering the problem of safe operation of industrial buildings and structures for various purposes.

The main purpose of developing the standard is to create a modern regulatory framework for the design and calculation of steel structures with bolted connections.

ORGANIZATION STANDARD

Approved and put into effect:

Introduction date 2005-01-01

1 area of ​​use

1.1 This standard applies to the design and calculation of steel structures with bolted field connections, including high-strength ones, designed for load-bearing and enclosing structures of buildings and structures for various purposes, perceiving permanent, temporary and special loads in climatic regions with design temperature up to -65°C and seismicity up to 9 points, operated both in slightly aggressive and medium aggressive and aggressive environments with the use of protective metal coatings.

1.2 The standard sets out the basic provisions for the design and calculation of bolted connections, working in shear and tension, shows the areas of rational use of bolts various diameters and strength classes.

2 Normative references

This standard uses references to the following normative documents:

Federal Law "On Technical Regulation" dated December 27, 2002 No. 184-FZ

for crushing, taking into account friction

Nbp- design force on crushing, determined by the formula

Qbh- design force perceived by friction forces, determined by the formula;

Tou- coefficient taking into account the reduction in the preload of the bolts after a total shear in the joint, taken equal to:

0.9 - differences in the nominal diameters of holes and bolts δ ≤ 0.3 mm;

0.85 - at δ = 1.0 mm;

0.80 - at δ = 2.0 mm;

0.75 - at δ = 3.0 mm;

n f- the number of friction surfaces of the connected elements.

7.5 Quantity nbolts in the joint under the action of a longitudinal force N should be determined by the formula

Nmin- the smaller of the design forcesNbs and NbhFor one bolt, calculated by the formulas and .

7.6 The strength of elements weakened for bolts should be checked taking into account the complete weakening of the sections by bolt holes.

7.7 In single shear connections, the number of bolts should be increased by 10% against the calculation.

7.8 Endurance calculation of friction shear joints should be performed in accordance with the requirements of clause 9.2 of SNiP II-23-81 *, classifying joints with steel elements with a tensile strength of more than 420 MPa to the 2nd group of structures, less than 420 MPa - to the 3rd group.

8 Flange connections

8.1 The recommendations of this section should be observed when designing, manufacturing and mounting assembly of flanged joints of open profile elements (I-beams, T-beams, channels, etc.) of steel structures of industrial buildings subject to tension, tension with bending with an unambiguous diagram of tensile stresses σ min/σ check≥ 0.5), as well as the action of local transverse forces.

The recommendations do not apply to flange connections: perceiving alternating loads, as well as repeatedly acting movable, vibrational or other types of loads with a number of cycles over 10 5 with a stress asymmetry factor in the connected elements R= σ min/σ check ≤ 0,8;

operated in a highly aggressive environment.

8.2 Flange connections should only be made with prestressed high strength bolts. Bolt preload value At 0 for calculations should be taken equal to

B 0 \u003d 0.9Bp=0.9RbhA bn,(11)

where In r- design tensile force of the bolt;

Rbh = 0.7 Rbun- design tensile strength of bolts;

Rbun- normative resistance of steel bolts;

A bn - net cross-sectional area of ​​the bolt.

8.3 For flange connections, high-strength bolts M20, M24 and M27 made of steel 40X "select" of KhL execution with standard tensile strength should be usedR bunnot more than 1080 MPa (110 kgf / mm 2), as well as high-strength nuts and washers for them according toGOST 22353-77- GOST 22356-77.

8.4 For flanges, sheet steel should be used in accordance with GOST 19903-74 * grade 09G2S-15 in accordance with GOST 19281-89 and 14G2AF-15 in accordance with TU 14-105-465-82 with guaranteed mechanical properties in the direction of the rolled thickness.

8.5 Flanges can be made of other grades of low-alloy steels according to GOST 19281-89, intended for building steel structures, while:

steel must be at least category 12;

temporary resistance and relative narrowing of steel in the direction of the thickness of the rolled products must beσ bz≥ 0,8 σ b, ψ z ≥ 20% (where σ b- normative value of temporary resistance for the base metal, taken according to standards or specifications).

a- from wide-shelf brands; b- from paired equal corners

8.10 When calculating the strength of bolts and flanges related to outdoor area, allocate sections of the flange, which are considered as T-shaped flange connections with a widthw(cm. ).

,(14)

where Nj- design forcej-th bolt of the outer zone, equal to

;(15)

here Nbj- design force onj-th bolt, determined from the condition of the strength of the connection by bolts

,(16)

a, β - coefficients taken according to the table. eight;

xj- bolt stiffness parameter, determined by the formula

;(17)

b j- axle distancej-th bolt to the edge of the weld;

Steel structures at the construction site are almost always connected using bolted connection and it has many advantages over other connection methods and, above all, welded connection - this is the ease of installation and quality control of the connection.

Among the shortcomings, one can note a large metal consumption compared to a welded joint, because. in most cases, overlays are needed. In addition, the bolt hole weakens the section.

There are a great many types of bolted connections, but in this article we will consider the classic connection used in building structures.

SNiP II-23-81 Steel structures

SP 16.13330.2011 Steel structures (Updated version of SNiP II-23-81)

SNiP 3.03.01-87 Bearing and enclosing structures

SP 70.13330.2011 Bearing and enclosing structures (Updated version of SNiP 3.03.01-87)

STO 0031-2004 Bolted connections. Product range and applications

STO 0041-2004 Bolted connections. Design and calculation

STO 0051-2006 Bolted connections. Manufacturing and installation

Types of bolted connections

According to the number of bolts: single-bolt and multi-bolt. I don't think it needs to be explained.

By the nature of the transfer of force from one element to another:

Not shear-resistant and shear-resistant (friction). To understand the meaning of this classification, let's consider how a bolted connection works in the general case when working in shear.

As you can see, the bolt compresses the 2nd plates and part of the effort is perceived by friction forces. If the bolts do not compress the plates strongly enough, then the plates slip and the force Q is perceived by the bolt.

The calculation of non-shear connections implies that the tightening force of the bolts is not controlled and the entire load is transmitted only through the bolt, without taking into account the resulting friction forces. Such a connection is called a connection without controlled tension of the bolts.

Shear or friction joints use high-strength bolts that tighten the plates with such a force that the load Q is transferred through frictional forces between the 2 plates. Such a connection can be friction or friction-shear, in the first case, only friction forces are taken into account in the calculation, in the second, friction forces and the shear strength of the bolt are taken into account. Although the friction-shear connection is more economical, it is very difficult to implement it in practice in a multi-bolt connection - there is no certainty that all the bolts can simultaneously bear the load on the shear, therefore it is better to calculate the friction connection without taking into account the shear.

At high shear loads, a friction connection is more preferable. the metal content of this compound is less.

Types of bolts by accuracy class and their application

Bolts of accuracy class A - these bolts are installed in holes drilled to the design diameter (i.e. the bolt fits into the hole without clearance). Initially, the holes are made smaller in diameter and gradually reamed to desired diameter. The diameter of the hole in such connections should not exceed the diameter of the bolt by more than 0.3 mm. It is extremely difficult to make such a connection, therefore, in building structures they are practically not used.

Bolts of accuracy class B (normal accuracy) and C (coarse accuracy) are installed in holes 2-3 mm larger than the diameters of the bolts. The difference between these bolts is the bolt diameter error. For bolts of accuracy class B, the actual diameter may deviate by no more than 0.52 mm, for bolts of accuracy class C up to 1 mm (for bolts with a diameter of up to 30 mm).

For building structures, as a rule, bolts of accuracy class B are used. in the realities of installation on a construction site, it is almost impossible to achieve high accuracy.

Types of bolts by strength and their application

For carbon steels the strength class is indicated by two digits separated by a dot.

There are the following bolt strength classes: 3.6; 3.8; 4.6; 4.8; 5.6; 5.8; 6.6; 8.8; 9.8; 10.9; 12.9.

The first digit in the bolt strength classification indicates the tensile strength of the bolt - one unit indicates a tensile strength of 100 MPa, i.e. the ultimate strength of a bolt of strength class 9.8 is 9x100=900 MPa (90 kg/mm²).

The second digit in the classification of the strength class indicates the ratio of the yield strength to the tensile strength in tens of percent - for a bolt of strength class 9.8, the yield strength is 80% of the tensile strength, i.e. the yield strength is 900 x 0.8 = 720 MPa.

What do these numbers mean? Let's look at the following diagram:

Here is a general case of steel tensile testing. The horizontal axis indicates the change in the length of the test specimen, and the vertical axis indicates the applied force. As you can see from the diagram, with an increase in force, the length of the bolt changes linearly only in the area from 0 to point A, the stress at this point is the yield point, then with a slight increase in load, the bolt stretches more, at point D the bolt breaks - this is the tensile strength . In building structures, it is necessary to ensure the operation of a bolted connection within the yield strength.

The strength class of the bolt must be indicated on the end or side surface of the bolt head.

If there is no marking on the bolts, then most likely these are bolts of a strength class below 4.6 (their marking is not required according to GOST). The use of bolts and nuts without marking is prohibited in accordance with SNiP 3.03.01.

On high-strength bolts, it is additionally indicated symbol swimming trunks.

For the bolts used, it is required to use nuts corresponding to their strength class: for bolts 4.6, 4.8 nuts of strength class 4 are used, for bolts 5.6, 5.8 nuts of strength class 5, etc. It is possible to replace nuts of one strength class with higher ones (for example, if it is more convenient to complete nuts of one strength class for an object).

When bolts are used only for shear, it is allowed to use the strength class of nuts with the strength class of bolts: 4 - at 5.6 and 5.8; 5 - at 8.8; 8 - at 10.9; 10 - at 12.9.

Stainless steel bolts are also marked on the bolt head. Steel class - A2 or A4 and tensile strength in kg / mm² - 50, 70, 80. For example A4-80: steel grade A4, strength 80 kg / mm² \u003d 800 MPa.

The strength class of bolts in building structures should be determined in accordance with Table D.3 of SP 16.13330.2011

Choice of bolt steel grade

The bolt steel grade should be assigned according to Table D.4 of SP 16.13330.2011

Selection of bolt diameter for constructionstructures

For building connections metal structures bolts with a hexagonal head of normal accuracy in accordance with GOST 7798 or increased accuracy in accordance with GOST 7805 with a large thread pitch of diameters from 12 to 48 mm, strength classes 5.6, 5.8, 8.8 and 10.9 in accordance with GOST 1759.4, hex nuts of normal accuracy in accordance with GOST 5915 or increased accuracy should be used in accordance with GOST 5927 strength classes 5, 8 and 10 in accordance with GOST 1759.5, round washers for them in accordance with GOST 11371 execution of 1 accuracy class A, as well as high-strength bolts, nuts and washers in accordance with GOST 22353 - GOST 22356 with diameters 16, 20, 22, 24, 27, 30, 36, 42 and 48 mm.

The diameter and number of bolts are selected so as to provide the necessary strength of the assembly.

If significant loads are not transmitted through the connection, then M12 bolts can be used. To connect loaded elements, it is recommended to use bolts from M16, for foundations from M20.

for M12 bolts - 40 mm;

for M16 bolts - 50 mm;

for M20 bolts - 60 mm;

for M24 bolts - 100 mm;

for M27 bolts - 140 mm.

Bolt hole diameter

For bolts of accuracy class A, the holes are made without clearance, but the use of such a connection is not recommended due to the great complexity of its manufacture. In building structures, as a rule, bolts of accuracy class B are used.

For bolts of accuracy class B, the hole diameter can be determined from the following table:

Bolt spacing

Distances when placing bolts should be taken in accordance with Table 40 of SP 16.13330.2011

At joints and nodes, bolts must be located closer to each other, and structural connecting bolts (used to connect parts without transferring significant loads) at maximum distances.

It is allowed to fasten parts with one bolt.

Choice of bolt length

We determine the length of the bolt as follows: add up the thicknesses of the elements to be joined, the thicknesses of the washers and nuts, and add 0.3d (30% of the bolt diameter) and then look at the assortment and select the nearest length (rounded up). According to building codes the bolt must protrude from the nut by at least one turn. A bolt that is too long cannot be used. there is a thread only at the end of the bolt.

For convenience, you can use the following table (from the Soviet reference book)

In shear bolted connections, with an outer element thickness of up to 8 mm, the thread must be outside the package of connected elements; in other cases, the bolt thread should not go deeper into the hole by more than half the thickness of the extreme element on the side of the nut or more than 5 mm. If the selected bolt length does not meet this requirement, then the bolt length must be increased to meet this requirement.

Here's an example:

The bolt works in shear, the thickness of the fastened elements is 2x12 mm, according to the calculation, a bolt with a diameter of 20 mm, a washer thickness of 3 mm, a spring washer thickness of 5 mm, and a nut thickness of 16 mm were adopted.

The minimum length of the bolt is: 2x12 + 3 + 5 + 16 + 0.3x20 = 54 mm, according to GOST 7798-70, we select the M20x55 bolt. The length of the threaded part of the bolt is 46 mm, i.e. the condition is not satisfied because the thread should go deep into the hole by no more than 5 mm, so we increase the length of the bolt to 2x12 + 46-5 = 65 mm. According to the norms, an M20x65 bolt can be accepted, but it is better to use an M20x70 bolt, then all the threads will be outside the hole. The spring washer can be replaced with a regular one and another nut can be added (very often this is done because the use of spring washers is limited).

Measures to prevent loosening of bolts

To ensure that the fastening does not loosen over time, it is required to use a 2nd nut or lock washers to prevent unscrewing of the bolts and nuts. If the bolt is in tension, then a 2nd bolt must be used.

There are also special nuts with a retaining ring or flange.

Do not use spring washers for oval holes.

Washer installation

No more than one washer should be installed under the nut. It is also allowed to install one washer under the bolt head.

Strength calculation of a bolted connection

Bolted connection can be divided into the following categories:

1) connection working in tension;

2) shear connection;

3) connection working on shear and tension;

4) friction connection (working in shear, but with a strong bolt tension)

Calculation of a bolted connection in tension

In the first case, the strength of the bolt is checked according to the formula 188 SP 16.13330.2011

where Nbt is load bearing capacity one tensile bolt;

Rbt is the design tensile strength of the bolt;

Calculation of a bolted shear connection

If the connection works on a slice, then you need to check 2 conditions:

shear calculation according to formula 186 SP 16.13330.2011

where Nbs is the bearing capacity of one bolt per shear;

Rbs is the design shear strength of the bolt;

Ab is the gross sectional area of ​​the bolt (accepted in accordance with Table D.9 of SP 16.13330.2011);

ns is the number of cuts of one bolt (if the bolt connects 2 plates, then the number of cuts is one, if 3, then 2, etc.);

γb is the operating condition coefficient of the bolted connection, taken in accordance with Table 41 of SP 16.13330.2011 (but not more than 1.0);

γc is the coefficient of working conditions, taken according to Table 1 of SP 16.13330.2011.

and calculation for collapse according to the formula 187 SP 16.13330.2011

where Nbp is the bearing capacity of one bolt in collapse;

Rbp is the design bearing strength of the bolt;

db- outside diameter bolt shaft;

∑t - the smallest total thickness of the connected elements, crushed in one direction (if the bolt connects the 2nd plates, then the thickness of one of the thinnest plates is taken, if the bolt connects 3 plates, then the sum of the thicknesses for the plates that transmit the load in one direction and compared with the thickness of the plate that transfers the load in the other direction and takes the smallest value);

γb is the coefficient of the working condition of the bolted connection, taken in accordance with Table 41 of SP 16.13330.2011 (but not more than 1.0)

γc is the coefficient of working conditions, taken according to Table 1 of SP 16.13330.2011.

Design resistance of bolts can be determined according to Table D.5 of SP 16.13330.2011

The design resistance Rbp can be determined from Table D.6 of SP 16.13330.2011

The calculated cross-sectional areas of the bolts can be determined from Table D.9 of SP 16.13330.2011

Calculation of a connection working in shear and tension

With the simultaneous action on the bolted connection of forces that cause shear and tension of the bolts, the most stressed bolt, along with the check according to the formula (188), should be checked according to the formula 190 SP 16.13330.2011

where Ns, Nt are the forces acting on the bolt, shearing and tensile, respectively;

Nbs, Nbt - design forces determined by formulas 186 and 188 of SP 16.13330.2011

Friction connection calculation

Friction joints, in which forces are transmitted through friction that occurs on the contacting surfaces of the elements to be joined due to the tension of high-strength bolts, should be used: in steel structures with a yield strength of more than 375 N / mm² and directly perceiving moving, vibrational and other dynamic loads; in multi-bolt connections, which are subject to increased requirements in terms of limiting deformability.

The design force that can be taken by each friction plane of the elements tightened by one high-strength bolt should be determined by the formula 191 SP 16.13330.2011

where Rbh is the design tensile strength of a high-strength bolt, determined in accordance with the requirements of 6.7 of SP 16.13330.2011;

Abn is the net cross-sectional area (accepted in accordance with Table D.9 of SP 16.13330.2011);

μ is the coefficient of friction between the surfaces of the parts to be joined (accepted according to Table 42 of SP 16.13330.2011);

γh is the coefficient taken according to Table 42 of SP 16.13330.2011

The number of required bolts for friction connection can be determined by the formula 192 SP 16.13330.2011

where n is the required number of bolts;

Qbh is the design force that one bolt takes (calculated according to the formula 191 SP 16.13330.2011, described a little higher);

k - the number of friction planes of the connected elements (usually 2 elements are connected through 2 overhead plates located with different sides, in this case k=2);

γc is the coefficient of working conditions, taken in accordance with Table 1 of SP 16.13330.2011;

γb - coefficient of working conditions, taken depending on the number of bolts required to absorb the force and taken equal to:

0.8 at n< 5;

0.9 for 5 ≤ n< 10;

1.0 for n ≤ 10.

Designation of a bolted connection in the drawings