SNiP II-23-81*
In return
SNiP II-V.3-72;
SNiP II-I.9-62; CH 376-67
STEEL STRUCTURES
1. GENERAL PROVISIONS
1.1. These standards must be observed when designing steel building structures of buildings and structures for various purposes.
The standards do not apply to the design of steel structures for bridges, transport tunnels and pipes under embankments.
When designing steel structures under special operating conditions (for example, structures of blast furnaces, main and process pipelines, special-purpose tanks, structures of buildings exposed to seismic, intense temperature effects or exposure to aggressive environments, structures of offshore hydraulic structures), structures of unique buildings and structures, as well as special types of structures (for example, prestressed, spatial, hanging), additional requirements must be observed that reflect the operating features of these structures, provided for by the relevant regulatory documents approved or agreed upon by the USSR State Construction Committee.
1.2. When designing steel structures, one must comply with SNiP standards for the protection of building structures from corrosion and fire safety standards for the design of buildings and structures. Increasing the thickness of rolled products and pipe walls in order to protect structures from corrosion and increase the fire resistance of structures is not allowed.
All structures must be accessible for observation, cleaning, painting, and must not retain moisture or impede ventilation. Closed profiles must be sealed.
1.3*. When designing steel structures you should:
select optimal technical and economic schemes of structures and cross-sections of elements;
use economical rolled profiles and efficient steels;
use, as a rule, unified standard or standard designs for buildings and structures;
use progressive structures (spatial systems made of standard elements; structures combining load-bearing and enclosing functions; prestressed, cable-stayed, thin-sheet and combined structures made of different steels);
provide for the manufacturability of manufacturing and installation of structures;
use designs that ensure the least labor intensity of their manufacture, transportation and installation;
provide, as a rule, for the in-line production of structures and their conveyor or large-block installation;
provide for the use of progressive types of factory connections (automatic and semi-automatic welding, flanged connections, with milled ends, bolted connections, including high-strength ones, etc.);
provide, as a rule, mounting connections with bolts, including high-strength ones; welded installation connections are allowed with appropriate justification;
comply with the requirements of state standards for structures of the corresponding type.
1.4. When designing buildings and structures, it is necessary to adopt structural schemes that ensure the strength, stability and spatial immutability of buildings and structures as a whole, as well as their individual elements during transportation, installation and operation.
1.5*. Steels and connection materials, restrictions on the use of S345T and S375T steels, as well as additional requirements for the supplied steel provided for by state standards and CMEA standards or technical specifications, should be indicated in working (DM) and detailing (DMC) drawings of steel structures and in the documentation for ordering materials.
Depending on the features of structures and their components, it is necessary to indicate the continuity class of steel when ordering.
1.6*. Steel structures and their calculations must meet the requirements of "Reliability of building structures and foundations. Basic provisions for calculation" and ST SEV 3972 – 83 "Reliability of building structures and foundations. Steel structures. Basic provisions for calculations."
1.7. Design schemes and basic calculation assumptions must reflect the actual operating conditions of steel structures.
Steel structures should generally be designed as unified spatial systems.
When dividing unified spatial systems into separate flat structures, the interaction of the elements with each other and with the base should be taken into account.
The choice of design schemes, as well as methods for calculating steel structures, must be made taking into account the effective use of computers.
1.8. Calculations of steel structures should, as a rule, be carried out taking into account inelastic deformations of steel.
For statically indeterminate structures, the calculation method for which taking into account inelastic deformations of steel has not been developed, the design forces (bending and torsional moments, longitudinal and transverse forces) should be determined under the assumption of elastic deformations of steel according to an undeformed scheme.
With an appropriate feasibility study, the calculation can be carried out using a deformed scheme that takes into account the influence of structural movements under load.
1.9. Elements of steel structures must have minimum cross-sections that meet the requirements of these standards, taking into account the range of rolled products and pipes. In composite sections established by calculation, the undervoltage should not exceed 5%.
2. MATERIALS FOR STRUCTURES AND CONNECTIONS
2.1*. Depending on the degree of responsibility of the structures of buildings and structures, as well as on the conditions of their operation, all structures are divided into four groups. Steels for steel structures of buildings and structures should be taken according to table. 50*.
Steel for structures erected in climatic regions I 1, I 2, II 2 and II 3, but operated in heated rooms, should be taken as for climatic region II 4 according to Table. 50*, with the exception of steel C245 and C275 for group 2 construction.
For flange connections and frame assemblies, rolled products should be used according to TU 14-1-4431 – 88.
2.2*. For welding steel structures the following should be used: electrodes for manual arc welding in accordance with GOST 9467-75*; welding wire according to GOST 2246 – 70*; fluxes according to GOST 9087 – 81*; carbon dioxide according to GOST 8050 – 85.
The welding materials and welding technology used must ensure that the tensile strength of the weld metal is not lower than the standard tensile strength value R un base metal, as well as the values of hardness, impact strength and relative elongation of the metal of welded joints, established by the relevant regulatory documents.
2.3*. Castings (supporting parts, etc.) for steel structures should be designed from carbon steel grades 15L, 25L, 35L and 45L, meeting the requirements for casting groups II or III according to GOST 977 – 75*, as well as from gray cast iron grades SCh15, SCh20, SCh25 and SCh30, meeting the requirements of GOST 1412 – 85.
2.4*. For bolted connections, steel bolts and nuts should be used that meet the requirements *, GOST 1759.4 – 87* and GOST 1759.5 – 87*, and washers that meet the requirements*.
Bolts should be assigned according to Table 57* and *, *, GOST 7796-70*, GOST 7798-70*, and when limiting the deformation of connections - according to GOST 7805-70*.
Nuts should be used in accordance with GOST 5915 – 70*: for bolts of strength classes 4.6, 4.8, 5.6 and 5.8 – nuts of strength class 4; for bolts of strength classes 6.6 and 8.8 – nuts of strength classes 5 and 6, respectively, for bolts of strength class 10.9 – nuts of strength class 8.
Washers should be used: round according to GOST 11371 – 78*, oblique according to GOST 10906 – 78* and spring normal according to GOST 6402 – 70*.
2.5*. The choice of steel grades for foundation bolts should be made according to, and their design and dimensions should be taken according to *.
Bolts (U-shaped) for fastening guy wires of antenna communication structures, as well as U-shaped and foundation bolts for supports of overhead power lines and distribution devices should be used from steel grades: 09G2S-8 and 10G2S1-8 according to GOST 19281 – 73* with an additional requirement for impact strength at a temperature of minus 60 ° C not less than 30 J/cm 2 (3 kgf × m/cm 2) in climatic region I 1; 09G2S-6 and 10G2S1-6 according to GOST 19281 – 73* in climatic regions I 2, II 2 and II 3; VSt3sp2 according to GOST 380 – 71* (since 1990 St3sp2-1 according to GOST 535 – 88) in all other climatic regions.
2.6*. Nuts for foundation and U-bolts should be used:
for bolts made of steel grades VSt3sp2 and 20 – strength class 4 according to GOST 1759.5 – 87*;
for bolts made of steel grades 09G2S and 10G2S1 – strength class not lower than 5 according to GOST 1759.5 – 87*. It is allowed to use nuts made of steel grades accepted for bolts.
Nuts for foundation and U-bolts with a diameter of less than 48 mm should be used in accordance with GOST 5915 – 70*, for bolts with a diameter of more than 48 mm – according to GOST 10605 – 72*.
2.7*. High-strength bolts should be used according to *, * and TU 14-4-1345 – 85; nuts and washers for them – according to GOST 22354 – 77* and *.
2.8*. For load-bearing elements of suspended coverings, guy wires for overhead lines and outdoor switchgears, masts and towers, as well as prestressing elements in prestressed structures, the following should be used:
spiral ropes according to GOST 3062 – 80*; GOST 3063 – 80*, GOST 3064 – 80*;
double lay ropes according to GOST 3066 – 80*; GOST 3067 – 74*; GOST 3068 – 74*; GOST 3081 – 80*; GOST 7669 – 80*; GOST 14954 – 80*;
closed load-bearing ropes according to GOST 3090 – 73*; GOST 18900 – 73* GOST 18901 – 73*; GOST 18902 – 73*; GOST 7675 – 73*; GOST 7676 – 73*;
bundles and strands of parallel wires formed from rope wire that meets the requirements of GOST 7372 – 79*.
2.9. The physical characteristics of materials used for steel structures should be taken in accordance with App. 3.
3. DESIGN CHARACTERISTICS OF MATERIALS AND CONNECTIONS
3.1*. The calculated resistances of rolled products, bent sections and pipes for various types of stress states should be determined using the formulas given in Table. 1*.
Table 1*
| Tense state | Symbol | Calculated resistance of rolled products and pipes | |
| stretching, | By yield strength | Ry | R y = R yn /g m |
| compression and bending | According to temporary resistance | R u | R u = R un /g m |
| R s | R s = 0.58Ryn/ g m | ||
|
End surface collapse (if fitted) |
Rp | R p = R un /g m | |
|
Local crushing in cylindrical hinges (trunnions) upon tight contact |
Rlp | Rlp= 0.5Run/ g m | |
|
Diametric compression of rollers (with free contact in structures with limited mobility) |
Rcd | Rcd= 0.025Run/ g m | |
|
Tension in the direction of rolled product thickness (up to 60 mm) |
R th | R th= 0.5Run/ g m | |
|
The designation adopted in table. 1*: |
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|
g m - reliability coefficient for the material, determined in accordance with clause 3.2*. |
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3.2*. The values of reliability coefficients for rolled material, bent sections and pipes should be taken according to table. 2*.
Table 2*
| State standard or technical conditions for rental | Reliability factor by material g m |
|
(except for steels S590, S590K); TU 14-1-3023 – 80 (for circle, square, stripe) |
1,025 |
|
(steel S590, S590K); GOST 380 – 71** (for a circle and a square with dimensions not included in TU 14-1-3023 – 80); GOST 19281 – 73* [for a circle and a square with a yield strength of up to 380 MPa (39 kgf/mm 2) and dimensions not included in TU 14-1-3023 – 80]; *; * |
1,050 |
|
GOST 19281 – 73* [for a circle and a square with a yield strength over 380 MPa (39 kgf/mm 2) and dimensions not included in TU 14-1-3023 – 80]; GOST 8731 – 87; TU 14-3-567 – 76 |
1,100 |
The calculated resistances in tension, compression and bending of sheet, wide-band universal and shaped rolled products are given in table. 51*, pipes - in table. 51, a. The calculated resistances of bent profiles should be taken equal to the calculated resistances of the rolled sheets from which they are made, while it is possible to take into account the hardening of the rolled sheet steel in the bending zone.
The design resistances of round, square and strip products should be determined according to table. 1*, taking values Ryn And R un equal, respectively, to the yield strength and tensile strength according to TU 14-1-3023 – 80, GOST 380 – 71** (since 1990 GOST 535 – 88) and GOST 19281 – 73*.
The calculated resistance of rolled products to crushing of the end surface, local crushing in cylindrical hinges and diametric compression of the rollers are given in Table. 52*.
3.3. The calculated resistances of castings made of carbon steel and gray cast iron should be taken according to table. 53 and 54.
3.4. The calculated resistances of welded joints for various types of joints and stress states should be determined using the formulas given in Table. 3.
Table 3
| Welded joints | Voltage state | Symbol | Calculated resistance of welded joints | |
| Butt |
Compression. Tension and bending during automatic, semi-automatic or manual welding with physical |
By yield strength | Rwy | Rwy=Ry |
|
seam quality control |
According to temporary resistance | R wu | R wu= R u | |
|
Stretching and bending during automatic, semi-automatic or manual welding |
By yield strength | Rwy | Rwy= 0.85Ry | |
| Shift | Rws | Rws= R s | ||
| With corner seams | Slice (conditional) | For weld metal | Rwf | |
| For metal fusion boundaries | Rwz | Rwz= 0.45Run | ||
|
Notes: 1. For seams made by hand welding, the values R wun should be taken equal to the values of the tensile strength of the weld metal specified in GOST 9467-75*. 2. For seams made by automatic or semi-automatic welding, the value of R wun should be taken according to table. 4* of these standards. 3. Reliability coefficient values for weld material g wm should be taken equal to: 1.25 – at values R wun no more than 490 MPa (5,000 kgf/cm2); 1.35 – at values R wun 590 MPa (6,000 kgf/cm2) or more. |
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The calculated resistances of butt joints of elements made of steel with different standard resistances should be taken as for butt joints made of steel with a lower value of standard resistance.
The calculated resistances of the weld metal of welded joints with fillet welds are given in Table. 56.
3.5. The calculated resistances of single-bolt connections should be determined using the formulas given in table. 5*.
The calculated shear and tensile strengths of the bolts are given in Table. 58*, collapse of elements connected by bolts, - in table. 59*.
3.6*. Design tensile strength of foundation bolts Rba
Rba = 0,5R. (1)
Design Tensile Strength of U-Bolts R bv, specified in clause 2.5*, should be determined by the formula
R bv = 0,45R un. (2)
The calculated tensile strength of foundation bolts is given in table. 60*.
3.7. Design tensile strength of high strength bolts Rbh should be determined by the formula
Rbh = 0,7Rbun, (3)
Where Rbun – the smallest temporary tensile strength of the bolt, taken according to the table. 61*.
3.8. Design tensile strength of high tensile steel wire Rdh, used in the form of bundles or strands, should be determined by the formula
Rdh = 0,63R un. (4)
3.9. The value of the calculated resistance (force) to tension of a steel rope should be taken equal to the value of the breaking force of the rope as a whole, established by state standards or technical specifications for steel ropes, divided by the reliability coefficient g m = 1,6.
Table 4*
| Wire grades (according to GOST 2246 – 70*) for automatic or semi-automatic welding | Powder grades | Standard values | |
| submerged (GOST 9087 – 81*) | in carbon dioxide (according to GOST 8050 – 85) or in its mixture with argon (according to GOST 10157 – 79*) | wires (according to GOST 26271 – 84) | weld metal resistance R wun, MPa (kgf/cm 2) |
|
Sv-08, Sv-08A |
– | – | 410 (4200) |
| – | – | 450 (4600) | |
| Sv-08G2S | PP-AN8, PP-AN3 | 490 (5000) | |
|
Sv-10NMA, Sv-10G2 |
Sv-08G2S* | – | 590 (6000) |
|
Sv-09HN2GMYU |
Sv-10ХГ2СМА Sv-08ХГ2ДУ | – | 685 (7000) |
|
* When welding with wire Sv-08G2S values R wun should be taken equal to 590 MPa (6000 kgf/cm 2) only for fillet welds with leg kf £ 8 mm in structures made of steel with a yield strength of 440 MPa (4500 kgf/cm2) or more. |
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Table 5*
| Design resistances of single-bolt connections | |||||
| Tense state | Symbol | shear and tension of class bolts | collapse of connected steel elements with a yield strength of up to 440 MPa | ||
| 4.6; 5.6; 6.6 | 4.8; 5.8 | 8.8; 10.9 | (4500 kgf/cm 2) | ||
| Rbs | R bs = 0.38R bun | Rbs= 0.4R bun | Rbs= 0.4R bun | – | |
|
Stretching |
R bt | R bt s = 0.38R bun | R bt = 0.38R bun | R bt = 0.38R bun | – |
| Rbp | |||||
|
a) bolts of accuracy class A |
– | – | – | ||
|
b) class B and C bolts |
– | – | – | ||
|
Note. It is allowed to use high-strength bolts without adjustable tension made of steel grade 40X “select”, while the calculated resistance Rbs And R bt should be determined as for bolts of class 10.9, and the design resistance as for bolts of accuracy classes B and C. High-strength bolts according to TU 14-4-1345 – 85 can only be used when working in tension. |
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4*. ACCOUNTING OPERATING CONDITIONS AND PURPOSE OF STRUCTURES
When calculating structures and connections, the following should be taken into account: reliability coefficients for the intended purpose g n adopted in accordance with the Rules for taking into account the degree of responsibility of buildings and structures when designing structures;
reliability factor g u= 1.3 for structural elements calculated for strength using design resistances R u;
working conditions coefficients g c and connection operating condition coefficients g b , taken according to the table. 6* and 35*, sections of these standards for the design of buildings, structures and structures, as well as app. 4*.
Table 6*
| Structural elements | Working conditions coefficients g with |
|
1. Solid beams and compressed elements of floor trusses under the halls of theaters, clubs, cinemas, under stands, under the premises of shops, book depositories and archives, etc. with the weight of the floors equal to or greater than the live load |
0,9 |
|
2. Columns of public buildings and supports of water towers |
0,95 |
|
3. Compressed main elements (except for supporting ones) of a composite T-section lattice from the corners of welded covering and ceiling trusses (for example, rafters and similar trusses) with flexibility l ³ 60 |
0,8 |
|
4. Solid beams when calculating general stability at j b 1,0 |
0,95 |
|
5. Tightenings, rods, braces, pendants made of rolled steel |
0,9 |
|
6. Elements of core structures of coatings and ceilings: |
|
|
a) compressed (with the exception of closed tubular sections) in stability calculations |
0,95 |
|
b) stretched in welded structures |
0,95 |
|
c) tensile, compressed, as well as butt linings in bolted structures (except for structures with high-strength bolts) made of steel with a yield strength of up to 440 MPa (4500 kgf/cm 2), bearing a static load, in strength calculations |
1,05 |
|
7. Solid composite beams, columns, as well as butt plates made of steel with a yield strength of up to 440 MPa (4500 kgf/cm2), bearing a static load and made using bolted connections (except for connections with high-strength bolts), in strength calculations |
1,1 |
|
8. Sections of rolled and welded elements, as well as linings made of steel with a yield strength of up to 440 MPa (4500 kgf/cm2) at joints made with bolts (except for joints with high-strength bolts) bearing a static load, in strength calculations: |
|
|
a) solid beams and columns |
1,1 |
|
b) core structures and floors |
1,05 |
|
9. Compressed lattice elements of spatial lattice structures from single equal-flange (attached by a larger flange) corners: |
|
|
a) attached directly to the belts with one flange using welds or two or more bolts placed along the angle: |
|
|
braces according to fig. 9*, a |
0,9 |
|
spacers according to fig. 9*, b, V |
0,9 |
|
braces according to fig. 9*, in, G, d |
0,8 |
|
b) attached directly to the belts with one shelf, one bolt (except for those indicated in item 9, in this table), and also attached through a gusset, regardless of the type of connection |
0,75 |
|
c) with a complex cross grid with single-bolt connections according to Fig. 9*, e |
0,7 |
|
10. Compressed elements from single angles, attached by one flange (for unequal angles only by a smaller flange), with the exception of the structural elements indicated in pos. 9 of this table, braces according to Fig. 9*, b, attached directly to the chords with welds or two or more bolts placed along the angle, and flat trusses from single angles |
0,75 |
|
11. Base plates made of steel with a yield strength of up to 285 MPa (2900 kgf/cm2), bearing a static load, thickness, mm: |
|
| 1,2 | |
|
b) over 40 to 60 |
1,15 |
|
c) over 60 to 80 |
1,1 |
|
Notes: 1. Operating conditions coefficients g with 1 should not be taken into account simultaneously when calculating. 2. Coefficients of operating conditions, given respectively in pos. 1 and 6, in; 1 and 7; 1 and 8; 2 and 7; 2 and 8,a; 3 and 6, c, should be taken into account simultaneously in the calculation. 3. Operating conditions coefficients given in pos. 3; 4; 6, a, c; 7; 8; 9 and 10, as well as in pos. 5 and 6, b (except for butt welded joints), the considered elements should not be taken into account when calculating connections. 4. In cases not specified in these standards, the formulas should take g c = 1. |
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5. CALCULATION OF ELEMENTS OF STEEL STRUCTURES FOR AXIAL FORCES AND BENDING
CENTRALLY EXTENSION AND CENTRALLY COMPRESSED ELEMENTS
5.1. Calculation of the strength of elements subject to central tension or compression by force N, except for those specified in clause 5.2, should be performed according to the formula
Calculation of the strength of sections in places of fastening of tensile elements from single angles, attached to one flange with bolts, should be performed according to formulas (5) and (6). In this case, the value g with in formula (6) should be taken according to adj. 4* of these standards.
5.2. Calculation of the strength of tensile steel structural elements with the ratio R u/g u > Ry, the operation of which is possible even after the metal reaches the yield point, should be carried out according to the formula
5.3. Calculation of stability of solid-wall elements subject to central compression by force N, should be performed according to the formula
Values j
at 0 £2.5
; (8)
at 2.5 £4.5
at > 4,5
. (10)
Numerical values j are given in table. 72.
5.4*. Rods made from single angles must be designed for central compression in accordance with the requirements set out in clause 5.3. When determining the flexibility of these rods, the radius of gyration of the angle section i and effective length lef should be taken according to paragraphs. 6.1 – 6.7.
When calculating the chords and lattice elements of spatial structures from single corners, the requirements of clause 15.10* of these standards should be met.
5.5. Compressed elements with solid walls of an open U-shaped section with l x 3l y , Where l x And l y – calculated flexibility of the element in planes perpendicular to the axes, respectively x– x And y -y (Fig. 1), it is recommended to strengthen them with slats or gratings, and the requirements of paragraphs must be met. 5.6 and 5.8*.
In the absence of strips or gratings, such elements, in addition to calculations using formula (7), should be checked for stability during flexural-torsional mode of buckling according to the formula
Where j y – buckling coefficient, calculated according to the requirements of clause 5.3;
With
(12)
Where 
;
a = a x/ h – relative distance between the center of gravity and the center of bending.
Here 
;
J w – sectorial moment of inertia of the section;
b i And t i – respectively the width and thickness of the rectangular elements making up the section.
For the section shown in Fig. 1, a, values 
And a
must be determined by the formulas:
Where b = b/h.
5.6. For composite compressed rods, the branches of which are connected by strips or gratings, the coefficient j relative to the free axis (perpendicular to the plane of the slats or gratings) should be determined by formulas (8) – (10) with replacement in them by ef. Meaning ef should be determined depending on the values lef given in table. 7.
Table 7
| Type | Scheme | Flexibility given lef composite through-section bars | ||||||
| sections | sections | with slats at | with bars | |||||
| J s l /( J b b) 5 | J s l /( J b b) ³ 5 | |||||||
| 1 | (14) | (17) |
 (20)
|
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| 2 | (15) | (18) |
 (21)
|
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| 3 | (16) |
 (19)
|
 (22)
|
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| Designations adopted in table. 7: | ||||||||
| b |
– distance between the axes of the branches; |
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| l |
– distance between the centers of the planks; |
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| l |
– the greatest flexibility of the entire rod; |
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| l 1, l 2, l 3 |
– flexibility of individual branches when bending them in planes perpendicular to the axes, respectively 1 – 1 , 2 – 2 and 3 – 3, in areas between welded strips (in the clear) or between the centers of the outer bolts; |
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| A |
– cross-sectional area of the entire rod; |
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| A d1 and A d2 |
– cross-sectional areas of the grid braces (with a cross grid – two braces) lying in planes perpendicular to the axes, respectively 1 – 1 And 2 – 2; |
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| A d |
– cross-sectional area of the lattice brace (with a cross lattice – two braces) lying in the plane of one face (for a triangular equilateral rod); |
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| a 1 And a 2 |
– coefficients determined by the formula |
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| Where |
– dimensions determined from Fig. 2; |
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|
n, n 1, n 2, n 3 |
– coefficients determined accordingly by formulas; |
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| Here |
J b1 And J b3 |
– moments of inertia of the sections of the branches relative to the axes, respectively 1 – 1 and 3 – 3 (for sections of types 1 and 3); |
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|
J b1 And J b2 |
– the same, two corners relative to the axes, respectively 1 – 1 and 2 – 2 (for section type 2); |
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|
– moment of inertia of the section of one bar relative to its own axis x– x (Fig. 3); |
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|
Js1 And J s2 |
– moments of inertia of the section of one of the strips lying in planes perpendicular to the axes, respectively 1 – 1 and 2 – 2 (for section type 2). |
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In composite rods with lattices, in addition to calculating the stability of the rod as a whole, the stability of individual branches in the areas between the nodes should be checked.
Flexibility of individual branches l 1 , l 2 And l 3 in the area between the slats there should be no more than 40.
If there is a solid sheet in one of the planes instead of slats (Fig. 1, b, V) the flexibility of the branch should be calculated by the radius of gyration of the half-section relative to its axis perpendicular to the plane of the slats.
In composite bars with lattices, the flexibility of individual branches between nodes should be no more than 80 and should not exceed the given flexibility lef the rod as a whole. It is allowed to accept higher values of branch flexibility, but not more than 120, provided that the calculation of such rods is carried out according to a deformed scheme.
5.7. Calculation of composite elements made of angles, channels, etc., connected tightly or through spacers, should be performed as solid-walled, provided that the largest distances in the areas between welded strips (in the clear) or between the centers of the outer bolts do not exceed:
for compressed elements 40 i
for tensile elements 80 i
Here the radius of inertia i corner or channel should be taken for T- or I-sections relative to an axis parallel to the plane of the spacers, and for cross sections – minimal.
In this case, at least two spacers should be installed within the length of the compressed element.
5.8*. Calculation of connecting elements (planks, gratings) of compressed composite rods should be carried out for a conditional transverse force Qfic, taken to be constant along the entire length of the rod and determined by the formula
Qfic = 7,15 × 10 -6 (2330 – E/Ry)N/j, (23)*
Where N – longitudinal force in the composite rod;
j – longitudinal bending coefficient accepted for a composite rod in the plane of the connecting elements.
Conditional shear force Qfic should be distributed:
if there are only connecting strips (grids), equally between the strips (grids) lying in planes perpendicular to the axis relative to which the stability is checked;
in the presence of a solid sheet and connecting strips (grids) – in half between the sheet and slats (lattices) lying in planes parallel to the sheet;
when calculating equilateral triangular composite rods, the conditional transverse force exerted on a system of connecting elements located in the same plane should be taken equal to 0.8 Qfic.
5.9. The calculation of connecting strips and their attachment (Fig. 3) should be performed as a calculation of elements of braceless trusses on:
force F, cutting bar, according to the formula
F = Q s l/b; (24)
moment M 1, bending the bar in its plane, according to the formula
M 1 = Q s l/2 (25)
Where Q s – conditional shear force applied to the bar of one face.
5.10. The calculation of connecting lattices should be carried out as a calculation of truss lattices. When calculating the cross braces of a cross lattice with struts (Fig. 4), the additional force should be taken into account Nad, arising in each brace from compression of the belts and determined by the formula
(26)
Where N – force in one branch of the rod;
A – cross-sectional area of one branch;
A d – cross-sectional area of one brace;
a – coefficient determined by the formula
a = a l 2 /(a 3 =2b 3) (27)
Where a, l And b – dimensions shown in Fig. 4.
5.11. The calculation of rods intended to reduce the design length of compressed elements must be performed for a force equal to the conventional transverse force in the main compressed element, determined by formula (23)*.
BENDING ELEMENTS
5.12. Calculation of the strength of elements (except for beams with a flexible wall, with a perforated wall and crane beams) bent in one of the main planes should be performed according to the formula
(28)
Shear stress value t in sections of bent elements must satisfy the condition
(29)
If the wall is weakened by bolt holes, the values t in formula (29) should be multiplied by the coefficient a , determined by the formula
a = a/(a – d), (30)
Where a – hole pitch;
b – hole diameter.
5.13. To calculate the strength of the beam wall in places where the load is applied to the upper chord, as well as in the support sections of the beam that are not reinforced with stiffeners, the local stress should be determined s loc according to the formula
(31)
Where F – calculated value of load (force);
lef – conditional length of load distribution, determined depending on the support conditions; for the case of support according to Fig. 5.
lef = b + 2t f, (32)
Where t f – thickness of the upper chord of the beam, if the lower beam is welded (Fig. 5, A), or the distance from the outer edge of the flange to the beginning of the internal rounding of the wall, if the lower beam is rolled (Fig. 5, b).
5.14*. For beam walls calculated using formula (28), the following conditions must be met:
Where – normal stresses in the midplane of the wall, parallel to the axis of the beam;
s y – the same, perpendicular to the axis of the beam, including s loc , determined by formula (31);
t xy – tangential stress calculated using formula (29) taking into account formula (30).
Voltages s x And s y , accepted in formula (33) with their own signs, as well as t xy should be determined at the same point in the beam.
5.15. Calculation of the stability of I-section beams that are bent in the plane of the wall and meet the requirements of paragraphs. 5.12 and 5.14*, should be performed according to the formula
Where W c – should be determined for a compressed belt;
j b – coefficient determined by adj. 7*.
When determining the value j b for the estimated length of the beam lef the distance between the points of fastening of the compressed belt from transverse displacements (nodes of longitudinal or transverse links, points of fastening of rigid flooring) should be taken; in the absence of connections lef = l(Where l – beam span) the design length of the cantilever should be taken as follows: lef = l in the absence of fastening the compressed belt at the end of the console in the horizontal plane (here l – console length); the distance between the fastening points of the compressed belt in the horizontal plane when fastening the belt at the end and along the length of the console.
5.16*. The stability of the beams does not need to be checked:
a) when transferring the load through a continuous rigid flooring, continuously resting on the compressed belt of the beam and securely connected to it (reinforced concrete slabs made of heavy, light and cellular concrete, flat and profiled metal flooring, corrugated steel, etc.);
b) in relation to the calculated length of the beam lef to the width of the compressed belt b, not exceeding the values determined by the formulas in table. 8* for beams of symmetrical I-section and with a more developed compressed chord, for which the width of the tensioned chord is at least 0.75 of the width of the compressed chord.
Table 8*
| Load application location | Largest values lef /b, for which stability calculations for rolled and welded beams are not required (at 1 £ h/b 6 and 15 £ b/t £35) |
| To the upper belt |
 (35)
|
| To the lower belt |
 (36)
|
| Regardless of the level of load application when calculating the beam section between braces or in pure bending |
 (37)
|
|
Designations adopted in table 8*: b And t – respectively the width and thickness of the compressed belt; h – distance (height) between the axes of the belt sheets. Notes: 1. For beams with chord connections on high-strength bolts, the values lef/b, obtained from the formulas in Table 8* should be multiplied by a factor of 1.2. 2. For beams with ratio b/t /t= 15. |
|
The fastening of the compressed belt in the horizontal plane must be designed for actual or conditional lateral force. In this case, the conditional lateral force should be determined:
when fixed at individual points according to formula (23)*, in which j should be determined with flexibility l = lef/i(Here i – radius of inertia of the section of the compressed belt in the horizontal plane), and N should be calculated using the formula
N = (Af + 0,25A W)Ry; (37, a)
with continuous fastening according to the formula
qfic = 3Qfic/l, (37, b)
Where qfic – conditional transverse force per unit length of the beam chord;
Qfic – conditional transverse force, determined by formula (23)*, in which it should be taken j = 1, a N – determined by formula (37,a).
5.17. Calculation of the strength of elements bent in two main planes should be performed according to the formula
(38)
Where x And y – coordinates of the section point under consideration relative to the main axes.
In beams calculated using formula (38), the stress values in the beam web should be checked using formulas (29) and (33) in the two main bending planes.
If the requirements of clause 5.16* are met, A checking the stability of beams bent in two planes is not required.
5.18*. Calculation of the strength of split beams of solid section made of steel with a yield strength of up to 530 MPa (5400 kgf/cm2), bearing a static load, subject to paragraphs. 5.19* – 5.21, 7.5 and 7.24 should be performed taking into account the development of plastic deformations according to the formulas
when bending in one of the main planes under tangential stresses t £0.9 R s(except for support sections)
(39)
when bending in two main planes under tangential stresses t £0.5 R s(except for support sections)
(40)
Here M, M x And M y – absolute values of bending moments;
c 1 – coefficient determined by formulas (42) and (43);
c x And c y – coefficients accepted according to table. 66.
Calculation in the support section of beams (with M = 0; M x= 0 and M y= 0) should be performed according to the formula
In the presence of a zone of pure bending in formulas (39) and (40) instead of the coefficients c 1, c x And with y should be taken accordingly:
from 1m = 0,5(1+c); c xm = 0,5(1+c x); with ym = 0,5(1+c y).
With simultaneous action in the moment section M and shear force Q coefficient from 1 should be determined using the formulas:
at t £0.5 R s c 1 = c; (42)
at 0.5 R s t £0.9 R s c 1 = 1,05b c , (43)
Where 
(44)
Here With – coefficient accepted according to the table. 66;
t And h – wall thickness and height, respectively;
a – coefficient equal to a = 0.7 for an I-section bent in the plane of the wall; a = 0 – for other types of sections;
from 1 – coefficient taken to be no less than one and no more than a coefficient With.
In order to optimize beams when calculating them taking into account the requirements of paragraphs. 5.20, 7.5, 7.24 and 13.1 coefficient values With, c x And with y in formulas (39) and (40) it is allowed to take less than the values given in table. 66, but not less than 1.0.
If the wall is weakened by bolt holes, the shear stress values t should be multiplied by the coefficient determined by formula (30).
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| Title of the document | SNiP II-23-81*. Design standards. Steel structures |
| Start date | 01.01.1982 |
| Acceptance date | 14.08.1981 |
| Cancellation date | 01.01.2013 |
| Status | Inactive |
| new document | DBN V.2.6-163:2010 cream divisions 15*-19, DSTU B V.2.6-194:2013 regarding sections 15*-19 |
| To replace | SNiP I-V.12-62, SNiP II-I.9-62, SN 247-63, SN 299-64, SN 316-65, SN 341-65, SN 347-66, SN 363-66, SN 376 -67 |
| Document type | SNiP (Building Norms and Rules) |
| Document code | II-23-81* |
| Developer | |
| Receiving authority | Central Research Institute of Building Structures named after. V. A. Kucherenko (TsNIISK named after V. A. Kucherenko) |
This document does not contain references to other regulatory documents.
SNiP II-23-81II-23-81*
GOSSTROY USSR
BUILDING REGULATIONS
SNiPII-23-81*
DESIGN STANDARDS
PARTII
Steel structures
CHAPTER 23
MOSCOW 1990
Approved
Decree of the USSR State Construction Committee
dated August 14, 1981.
№ 144
DEVELOPED BY TsNIISK im. Kucherenko with the participation of TsNIIproektstalkonstruktsii of the USSR State Construction Committee, MISI named after. V.V. Kuibyshev of the USSR Ministry of Higher Education, the Energosetproekt Institute and the Mosgidrostal Design Bureau of the USSR Ministry of Energy.
These standards were developed as a development of GOST 27751-88 “Reliability of building structures and foundations. Basic provisions for calculations" and ST SEV 3972-83 "Reliability of building structures and foundations. Steel structures. Basic provisions for calculation."
With the entry into force of these building codes and regulations, the following become invalid:
SNiP II-V.3-72 “Steel structures. Design standards";
changes to SNiP II-B.3-72 “Steel structures. Design standards” approved by the resolutions of the USSR State Construction Committee:
SNiP II-I.9-62 “Power transmission lines with voltage above 1 kV. Design standards" (section "Design of steel structures for overhead power transmission line supports");
changes to SNiP II-I.9-62 “Power transmission lines with voltage above 1 kV. Design standards”, approved by the Decree of the USSR State Construction Committee dated April 10, 1975;
“Guidelines for the design of metal structures of antenna structures of communication facilities” (SN 376-67).
Amendments were made to SNiP II-23-81*, approved by resolutions of the USSR State Construction Committee No. 120 of July 25, 1984, No. 218 of December 11, 1985, No. 69 of December 29, 1986, No. 132 of July 8, 1988. , No. 121 of July 12, 1989
The main letter designations are given in *.
Sections, paragraphs, tables, formulas, appendices and captions to drawings to which changes have been made are marked in these building codes and regulations with an asterisk.
Editors - engineers F. M. Shlemin, IN. P. Poddubny
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DEVELOPED BY TsNIISK im. Kucherenko with the participation of TsNIIproektstalkonstruktsii of the USSR State Construction Committee, MISI named after. V.V. Kuibyshev of the USSR Ministry of Higher Education, the Energosetproekt Institute and the Mosgidrostal Design Bureau of the USSR Ministry of Energy.
These standards were developed as a development of GOST 27751-88 “Reliability of building structures and foundations. Basic provisions for calculations" and ST SEV 3972-83 "Reliability of building structures and foundations. Steel structures. Basic provisions for calculation."
With the entry into force of these building codes and regulations, the following become invalid:
- SNiP II-V.3-72 “Steel structures. Design standards";
- changes to SNiP II-B.3-72 “Steel structures. Design standards” approved by the resolutions of the USSR State Construction Committee:
No. 150 of September 12, 1975;
No. 94 of June 24, 1976;
No. 211 of October 31, 1978;
No. 250 of December 27, 1978;
No. 2 of January 25, 1980;
No. 104 of July 14, 1980;
No. 130 of July 31, 1981; - SNiP II-I.9-62 “Power transmission lines with voltage above 1 kV. Design standards" (section "Design of steel structures for overhead power transmission line supports");
- changes to SNiP II-I.9-62 “Power transmission lines with voltage above 1 kV. Design standards”, approved by the Decree of the USSR State Construction Committee dated April 10, 1975;
- “Guidelines for the design of metal structures of antenna structures of communication facilities” (SN 376-67).
Amendments were made to SNiP II-23-81*, approved by resolutions of the USSR State Construction Committee No. 120 of July 25, 1984, No. 218 of December 11, 1985, No. 69 of December 29, 1986, No. 132 of July 8, 1988. , No. 121 of July 12, 1989
The main letter designations are given in the appendix. 9*.
Sections, paragraphs, tables, formulas, appendices and captions to drawings to which changes have been made are marked in these building codes and regulations with an asterisk.
Editors - engineers F.M. Shlemin, V.P. Poddubny (Gosstroy USSR), Doctor of Engineering. science prof. V.A. Baldin, Ph.D. tech. Sciences G.E. Velsky (TsNIISK Gosstroy USSR), engineer. EAT. Bukharin (“Energosetproekt” Ministry of Energy of the USSR), engineer. N.V. Shevelev (SKB Mosgidrostal, Ministry of Energy of the USSR).
When using a regulatory document, one should take into account the approved changes to building codes and regulations and state standards published in the journal “Bulletin of Construction Equipment”, “Collection of Amendments to Construction Codes and Rules” of the USSR State Construction Committee and the information index “USSR State Standards” of the USSR State Standard.
1. General Provisions
2. Materials for structures and connections
3. Design characteristics of materials and connections
4*. Taking into account operating conditions and purpose of structures
5. Calculation of steel structure elements for axial forces and bending
6. Design lengths and maximum flexibility of steel structure elements
7. Checking the stability of walls and waist sheets of bending and compressed elements
8. Calculation of sheet structures
9. Calculation of elements of steel structures for endurance
10. Strength calculation of steel structure elements taking into account brittle fracture
11. Calculation of connections of steel structures
12. General requirements for the design of steel structures
13. Additional requirements for the design of industrial buildings and structures
14. Additional requirements for the design of residential and public buildings and structures
15*. Additional requirements for the design of overhead power line supports, structures of open switchgears and transport contact lines
Designations adopted in table. 50*:
a) shaped steel with a thickness of up to 11 mm, and upon agreement with the manufacturer - up to 20 mm; sheet - all thicknesses;
b) the requirement to limit the carbon equivalent according to GOST 27772-88 for thicknesses over 20 mm;
c) the requirement to limit the carbon equivalent according to GOST 27772-88 for all thicknesses;
d) for region II 4, for unheated buildings and structures operated at outdoor temperatures, use rolled products with a thickness of no more than 10 mm;
e) with a rolled product thickness of no more than 11 mm, category 3 steel may be used;
f) except for the supports of overhead lines, outdoor switchgear and KS;
g) rolled products up to 10 mm thick and taking into account the requirements of section. 10;
i) except for region II 4 for unheated buildings and structures operated at outside air temperature.
The "+" sign means that this steel should be used; the sign “—” means that this steel should not be used in the specified climatic region.
Notes: 1. The requirements of this table do not apply to steel structures of special structures: main and process pipelines, special-purpose tanks, casings of blast furnaces and air heaters, etc. Steels for these structures are established by the relevant SNiP or other regulatory documents.
2. The requirements of this table apply to sheet metal with a thickness of 2 mm and shaped steel with a thickness of 4 mm in accordance with GOST 27772-88, long products (round, square, strip) in accordance with TU 14-1-3023-80, GOST 380-71* * (since 1990 GOST 535-88) and GOST 19281-73*. The specified steel categories refer to rolled products with a thickness of at least 5 mm. For thicknesses less than 5 mm, the steels listed in the table are used without requirements for impact strength.
For structures of all groups, except for group 1 and supports of overhead lines and outdoor switchgear, in all climatic regions except I 1, it is allowed to use rolled products with a thickness of less than 5 mm from steel C235 in accordance with GOST 27772-88.
3. Climatic areas of construction are established in accordance with GOST 16350-80 "Climate of the USSR. Zoning and statistical parameters of climatic factors for technical purposes." The calculated temperatures indicated in the head of the table in brackets correspond to the outside air temperature of the corresponding area, which is taken to be the average temperature of the coldest five-day period in accordance with the instructions of SNiP for construction climatology and geophysics.
4. Structures that are directly exposed to dynamic, vibration or moving loads include structures or their elements that are subject to endurance calculations or calculated taking into account dynamic coefficients.
5. With an appropriate feasibility study, steels S345, S375, S440, S590, S590K, 16G2AF can be ordered as steels with increased corrosion resistance (with copper) - S345D, S375D, S440D, S590D, S590KD, 16G2AFD.
6. The use of heat-strengthened shaped bars made from steel S345T and S375T by rolling heating, supplied according to GOST 27772-88 as steel S345 and S375, is not allowed in structures that are subject to metallization or plastic deformation during manufacture at temperatures above 700°C.
7. Seamless hot-deformed pipes in accordance with GOST 8731-87 may be used only for elements of special supports of large transitions of power lines with a height of more than 60 m, for antenna communication structures and other special structures, and the following steel grades should be used:
in all climatic regions, except I 1, I 2, II 2 and II 3, grade 20 according to GOST 8731-87, but with an additional requirement for impact strength at a temperature of minus 20°C of at least 30 J/cm² (3 kgs×m/ cm²);
in climatic regions I 2, II 2 and II 3 - grade 09G2S according to GOST 8731-87, but with an additional requirement for impact strength at a temperature of minus 40°C of at least 40 J/cm² (4 kgf×m/cm²) for wall thickness up to 9 mm and 35 J/cm² (3.5 kgf×m/cm²) with a wall thickness of 10 mm or more.
It is not allowed to use seamless hot-deformed pipes made from ingots marked with the letter “L” that have not been tested by non-destructive methods.
8. Long products (round, square, strip) according to TU 14-1-3023-80, GOST 380-71* (since 1990 GOST 535-88) and GOST 19281-73* are subject to the same requirements as for shaped rolled products of the same thickness according to GOST 27772-88. The correspondence of steel grades according to TU 14-1-3023-80, GOST 380-71*, GOST 19281-73* and GOST 19282-73* to steels according to GOST 27772-88 should be determined from the table. 51, b.