Gross sectional area. General provisions

4.5. The estimated length of the elements should be determined by multiplying their free length by a factor

according to paragraphs 4.21 and 6.25.

4.6. Composite elements on pliable joints, supported by the entire cross section, should be calculated for strength and stability according to formulas (5) and (6), while also being determined as the total areas of all branches. The flexibility of the constituent elements should be determined taking into account the compliance of the joints according to the formula

(11)

		flexibility of the entire element relative to the axis (Fig. 2), calculated from the effective length without compliance;
			flexibility of a separate branch relative to the axis I - I (see Fig. 2), calculated from the estimated length of the branch; with less than seven thicknesses () branches take =0;
			coefficient of reduction of flexibility, determined by the formula

(12)

		width and height of the cross section of the element, cm;
			the estimated number of seams in the element, determined by the number of seams over which the mutual shift of the elements is summed up (in Fig. 2, a - 4 seams, in Fig. 2, b - 5 seams);
			estimated length of the element, m;
			the estimated number of cuts of bonds in one seam per 1 m of the element (for several seams with a different number of cuts, the average number of cuts for all seams should be taken);
			the coefficient of compliance of the joints, which should be determined by the formulas of Table 12.

When determining the diameter of nails, no more than 0.1 of the thickness of the connected elements should be taken. If the size of the pinched ends of the nails is less than 4, then the cuts in the seams adjacent to them are not taken into account in the calculation. The value of joints on steel cylindrical dowels should be determined by the thickness of the thinner of the connected elements.

Rice. 2. Components

a - with gaskets; b - without gaskets

Table 12

Connection type	Coefficient at
	central compression	bending compression


2. Steel cylindrical pins:
a) the diameter of the thickness of the connected elements
b) diameter > thickness of connected elements
3. Oak cylindrical dowels
4. Oak lamellar dowels

Note: The diameters of nails and dowels, the thickness of the elements, the width and thickness of the lamellar dowels should be taken in cm.

When determining the diameter of oak cylindrical dowels, no more than 0.25 of the thickness of the thinner of the connected elements should be taken.

Ties in the seams should be spaced evenly along the length of the element. In hinged rectilinear elements, it is allowed to put connections in the middle quarters of the length in half the amount, introducing into the calculation according to formula (12) the value taken for the extreme quarters of the length of the element.

The flexibility of a composite element calculated by formula (11) should be taken no more than the flexibility of individual branches, determined by the formula

(13)

		the sum of the gross moments of inertia of the cross sections of individual branches relative to their own axes parallel to the axis (see Fig. 2);
			gross sectional area of the element;
			Estimated element length.

The flexibility of a composite element relative to the axis passing through the centers of gravity of the sections of all branches (the axis in Fig. 2) should be determined as for a solid element, i.e. without taking into account the compliance of the bonds, if the branches are loaded evenly. In the case of unevenly loaded branches, paragraph 4.7 should be followed.

If the branches of a composite element have a different cross section, then the calculated flexibility of the branch in formula (11) should be taken equal to:

(14)

the definition is given in Fig.2.

4.7. Composite elements on pliable joints, some of the branches of which are not supported at the ends, can be calculated for strength and stability according to formulas (5), (6) subject to the following conditions:

a) the cross-sectional area of \u200b\u200bthe element and should be determined by the cross section of the supported branches;

b) the flexibility of the element relative to the axis (see Fig. 2) is determined by the formula (11); in this case, the moment of inertia is taken taking into account all branches, and the area - only supported ones;

c) when determining the flexibility relative to the axis (see Fig. 2), the moment of inertia should be determined by the formula

moments of inertia of the cross sections of supported and unsupported branches, respectively.

4.8. The calculation for the stability of centrally compressed elements of a section with a variable height should be performed according to the formula

		gross cross-sectional area with maximum dimensions;
		coefficient taking into account the variability of the section height, determined according to Table 1, Appendix 4 (for elements of a constant section);
		buckling coefficient determined according to item 4.3 for flexibility corresponding to the section with maximum dimensions.

Bending elements

4.9. Calculation of bending elements, secured against buckling of the flat form of deformation (see clauses 4.14 and 4.15), for strength under normal stresses should be carried out according to the formula

		calculated bending moment;
		design resistance to bending;
		design modulus of the element's cross section. For solid members for bending components on yielding joints, the calculated modulus of modulus should be taken equal to the net modulus multiplied by the factor ; values for elements composed of identical layers are given in Table 13. When determining the weakening of the sections, located on the section of the element with a length of up to 200 mm, they are taken combined in one section.

Table 13

Coefficient notation	Number of layers per element	The value of the coefficients for the calculation of bending components during spans, m








Note. For intermediate values of the span and the number of layers, the coefficients are determined by interpolation.

4.10. Calculation of bending elements for shearing strength should be performed according to the formula

		design shear force;
		static gross moment of the shifted part of the cross section of the element relative to the neutral axis;
		gross moment of inertia of the cross section of the element relative to the neutral axis;
		calculated width of the section of the element;
		design resistance to shearing in bending.

4.11. The number of cuts , evenly spaced in each seam of a composite element in a section with an unambiguous diagram of transverse forces, must satisfy the condition

(19)

		the calculated bearing capacity of the connection in this seam;
		bending moments in the initial and final sections of the section under consideration.

Note. If there are bonds of different bearing capacity in the seam, but

identical in nature of work (for example, dowels and nails), bearing

their abilities should be summed up.

4.12. The calculation of elements of a solid section for strength in oblique bending should be carried out according to the formula

(20)

	components of the calculated bending moment for the main axes of the section and
	section modulus netto about the main axes of the section and

4.13. Glued curvilinear elements that are bent by a moment that reduces their curvature should be checked for radial tensile stresses according to the formula

(21)

		normal stress in the extreme fiber of the stretched zone;
		normal stress in the intermediate fiber of the section for which the radial tensile stresses are determined;
		the distance between the extreme and considered fibers;
		the radius of curvature of the line passing through the center of gravity of the diagram of normal tensile stresses, enclosed between the extreme and considered fibers;
		calculated wood tensile strength across the fibers, taken according to clause 7 of Table 3.

4.14. Calculation for the stability of the flat form of deformation of bent elements of rectangular section should be carried out according to the formula

		maximum bending moment in the section under consideration
		maximum gross modulus in the area under consideration

The coefficient for bending elements of rectangular cross section, hinged against displacement from the bending plane and fixed against rotation around the longitudinal axis in the reference sections, should be determined by the formula

		the distance between the support sections of the element, and when fixing the compressed edge of the element at intermediate points from displacement from the bending plane - the distance between these points;
		cross section width;
		the maximum height of the cross section on the site;
		coefficient depending on the shape of the curve of bending moments in the section, determined according to tables 2, 3, appendix 4 of these standards.

When calculating bending moments with a height linearly changing along the length and a constant width of the cross section, which do not have fastenings from the plane along the edge stretched from the moment, or with the coefficient according to the formula (23) should be multiplied by an additional coefficient. The values are given in Table 2, Appendix 4. At =1.

When reinforcing from the bending plane at intermediate points of the stretched edge of the element in the section, the coefficient determined by formula (23) should be multiplied by the coefficient:

:= (24)

		the central angle in radians that defines the section of the element of circular shape (for rectilinear elements);
		the number of intermediate reinforced (with the same step) points of the stretched edge on the section (for the value should be taken equal to 1).

4.15. Checking the stability of the flat form of deformation of bending elements of an I-beam or box-shaped cross-section should be carried out in cases where

width of the compressed belt of the cross section.

The calculation should be made according to the formula

		coefficient of longitudinal bending from the plane of bending of the compressed chord of the element, determined according to clause 4.3;
		design compressive strength;
		gross modulus of the cross section; in the case of plywood walls, the reduced modulus of resistance in the bending plane of the element.

Elements subjected to axial force with bending

4.16. Calculation of eccentric-tensioned and tension-bent elements should be made according to the formula

(27)

4.17. Calculation for the strength of eccentrically compressed and compressed-bent elements should be made according to the formula

(28)

Notes: 1. For hinged elements with symmetrical diagrams

bending moments sinusoidal, parabolic, polygonal

and close to them outlines, as well as for console elements should

determine by formula

			coefficient varying from 1 to 0, taking into account the additional moment from the longitudinal force due to the deflection of the element, determined by the formula
		bending moment in the design section without taking into account the additional moment from the longitudinal force;
		coefficient determined by formula (8) p.4.3.

2. In cases where bending moment diagrams in hinged elements have a triangular or rectangular shape, the coefficient according to formula (30) should be multiplied by the correction factor:

(31)

3. With an asymmetric loading of hinged elements, the magnitude of the bending moment should be determined by the formula

(32)

		bending moments in the calculated section of the element from the symmetrical and skew-symmetric components of the load;
		coefficients determined by formula (30) at slenderness values corresponding to symmetrical and oblique buckling forms.

4. For elements of a section variable in height, the area in formula (30) should be taken for the maximum section in height, and the coefficient should be multiplied by the coefficient taken from Table 1, Appendix 4.

5. When the ratio of stresses from bending to stresses from compression is less than 0.1, the compressively-bent elements should also be checked for stability according to formula (6) without taking into account the bending moment.

4.18. The calculation for the stability of the flat form of deformation of the compressed-bent elements should be carried out according to the formula

(33)

		gross area with the maximum dimensions of the section of the element on the site ;

		for elements without fixing the stretched zone from the deformation plane and for elements having such fixings;
		buckling coefficient determined by formula (8) for the flexibility of the section of the element with the estimated length from the plane of deformation;
		coefficient determined by formula (23).

If there are fastenings in the element in the area from the deformation plane on the side of the edge stretched from the moment, the coefficient should be multiplied by the coefficient determined by the formula (24), and the coefficient - by the coefficient by the formula

(34)

When calculating elements of a section with a variable height that do not have fastenings from the plane along an edge stretched from the moment or at , the coefficients and determined by formulas (8) and (23) should be additionally multiplied, respectively, by the coefficients and given in Tables 1 and 2 appendix .four. At

4.19. In composite compressed-bent elements, the stability of the most stressed branch should be checked, if its estimated length exceeds seven branch thicknesses, according to the formula

(35)

The stability of a compressively-bent composite element from the bending plane should be checked using formula (6) without taking into account the bending moment.

4.20. The number of bond cuts , evenly spaced in each seam of a compressed-bent composite element in a section with an unambiguous diagram of transverse forces when a compressive force is applied over the entire section, must satisfy the condition

where the coefficient is taken from Table 1, Appendix 4.

	gross static moment of the shifted part of the cross section relative to the neutral axis; with hinged ends, as well as with hinged fastening at intermediate points of the element - 1; with one hinged and the other pinched end - 0.8; with one pinched and other free loaded end - 2.2; with both pinched ends - 0.65. In the case of a longitudinal load distributed evenly along the length of the element, the coefficient should be taken equal to: with both hinged ends - 0.73; with one pinched and the other free end - 1.2. The estimated length of intersecting elements connected to each other at the intersection should be taken equal to: when checking stability in the plane of structures - the distance from the center of the node to the point of intersection of the elements; when checking stability from the plane of the structure: a) in case of intersection of two compressed elements - the full length of the element;	Name of structural elements	Ultimate Flexibility

1. Compressed chords, support braces and truss support posts, columns
2. Other compressed elements of trusses and other through structures
3. Compressed link elements
4. Stretched truss belts in the vertical plane
5. Other tension elements of trusses and other through structures
For overhead power lines

The value should be taken at least 0.5;

c) in the case of intersection of a compressed element with a stretched element of equal magnitude - the greatest length of the compressed element, measured from the center of the node to the point of intersection of the elements.

If the intersecting elements have a composite section, then the corresponding slenderness values determined by formula (11) should be substituted into formula (37).

4.22. The flexibility of the elements and their individual branches in wooden structures should not exceed the values \u200b\u200bspecified in Table 14.

Features of the calculation of glued elements

plywood with wood

4.23. The calculation of glued elements made of plywood with wood should be carried out according to the reduced cross-section method.

4.24. The strength of the stretched plywood sheathing of slabs (Fig. 3) and panels should be checked according to the formula

moment of section modulus reduced to plywood, which should be determined in accordance with the instructions of clause 4.25.

4.25. The reduced modulus of the cross section of glued plywood boards with wood should be determined by the formula

distance from the center of gravity of the reduced section to the outer edge of the skin;

Fig.3. Cross section of glued plywood and wood boards

static moment of the shifted part of the reduced section relative to the neutral axis;

design chipping resistance of wood along the fibers or plywood along the fibers of the outer layers;

the calculated section width, which should be taken equal to the total width of the frame ribs.

BUT- gross sectional area;

A bn- net bolt cross-sectional area;

A d- sectional area of the brace;

A f- sectional area of the shelf (belt);

A n- net sectional area;

Aw- sectional area of the wall;

Awf- cross-sectional area for fillet weld metal;

Awz- cross-sectional area for the metal of the fusion boundary;

E- elastic modulus;

F- strength;

G- shear modulus;

Jb- moment of inertia of the branch section;

J m; Jd- moments of inertia of the sections of the belt and the brace of the truss;

Js- the moment of inertia of the section of the rib, strap;

Jsl- moment of inertia of the section of the longitudinal rib;

J t- moment of inertia of torsion of the beam, rail;

J x; Jy- moments of inertia of the gross section about the axes, respectively x-x and y-y;

Jxn; Jyn- the same, net sections;

M- moment, bending moment;

Mx; M y- moments about the axes, respectively x-x and y-y;

N- longitudinal force;

N ad- additional effort;

Nbm- longitudinal force from the moment in the branch of the column;

Q- transverse force, shear force;

Qfic- conditional transverse force for connecting elements;

Qs- conditional transverse force attributable to the system of slats located in the same plane;

Rba- design tensile strength of foundation bolts;

Rbh- design tensile strength of high-strength bolts;

Rbp- design resistance to collapse of bolted joints;

Rbs- design shear strength of bolts;

Rbt- design tensile strength of bolts;

R bun- normative resistance of steel bolts, taken equal to the tensile strength σ in according to state standards and specifications for bolts;

Rbv- design tensile strength of U-bolts;

Rcd- design resistance to diametrical compression of the rollers (with free contact in structures with limited mobility);

R dh- design tensile strength of high-strength wire;

Rlp- calculated resistance to local collapse in cylindrical hinges (trunnions) with tight contact;

Rp- design resistance of steel to crushing of the end surface (if there is a fit);

Rs- design resistance of steel to shear;

Rth- design tensile strength of steel in the direction of the rolled thickness;

R u- design resistance of steel to tension, compression, bending in terms of temporary resistance;

Run- steel tensile strength taken equal to the minimum value σ in according to state standards and specifications for steel;

Rwf- design resistance of fillet welds to a cut (conditional) for the weld metal;

Rwu- design resistance of butt welded joints to compression, tension, bending in terms of tensile strength;

R wun- normative resistance of the weld metal in terms of temporary resistance;

Rws- design shear resistance of butt welded joints;

Rwy- design resistance of butt welded joints to compression, tension and bending in terms of yield strength;

Rwz- design resistance of fillet welds to a cut (conditional) for the metal of the fusion boundary;

Ry- design resistance of steel to tension, compression, bending at the yield strength;

Ryn- the yield strength of steel, taken equal to the value of the yield strength σ t according to state standards and specifications for steel;

S- static moment of the shifted part of the gross section relative to the neutral axis;

W x; W y- moments of resistance of the gross section relative to the axes, respectively x-x and y-y;

Wxn; Wyn- moments of resistance of the net section relative to the axes, respectively x-x and y-y;

b- width;

bef- estimated width;

bf- width of the shelf (belt);

b h- width of the protruding part of the rib, overhang;

c; c x; c y- coefficients for calculating the strength, taking into account the development of plastic deformations during bending about the axes, respectively x-x, y-y;

e- force eccentricity;

h- height;

hef- estimated wall height;

hw- wall height;

i- radius of inertia of the section;

imin- the smallest radius of inertia of the section;

i x; i y are the radii of inertia of the section relative to the axes, respectively x-x and y-y;

kf- leg fillet weld;

l- length, span;

lc- the length of the rack, column, spacers;

ld- brace length;

lef- estimated, conditional length;

lm- length of the truss belt panel or column;

ls- strap length;

l w- length of the weld;

l x; l y- estimated lengths of the element in planes perpendicular to the axes, respectively x-x and y-y;

m- relative eccentricity ( m = eA / Wc);

mef- reduced relative eccentricity ( mef = mη);

r- radius;

t- thickness;

t f- thickness of the shelf (belt);

tw- wall thickness;

β f and βz- coefficients for calculating the fillet weld, respectively, for the weld metal and for the metal of the fusion boundary;

γb- coefficient of connection operation conditions;

γ c- coefficient of working conditions;

γn- reliability coefficient for the intended purpose;

γ m- reliability coefficient for the material;

u- reliability factor in calculations of temporary resistance;

η - coefficient of influence of the section shape;

λ - flexibility ( λ = lef / i);

conditional flexibility();

λ ef- reduced flexibility of the rod through section;

Conditional reduced flexibility of a bar through section ( );

Conditional wall flexibility ( );

The greatest conditional flexibility of the wall;

λ x; λ y- design slenderness of the element in planes perpendicular to the axes, respectively x-x and y-y;

v- coefficient of transverse deformation of steel (Poisson);

σ loc- local tension;

σ x; y- normal stresses parallel to the axes, respectively x-x and y-y;

τxy- shear stress;

φ (X, y) - buckling coefficient;

φb- coefficient of reduction of design resistances in the bending-torsional form of buckling of beams;

φe- coefficient of reduction of design resistances at eccentric compression.

1. General Provisions. 2 2. Materials for structures and connections. 3 3. Design characteristics of materials and compounds. 4 4*. Accounting for working conditions and purpose of structures. 6 5. Calculation of elements of steel structures for axial forces and bending. 7 Centrally tensioned and centrally compressed members.. 7 Bending members.. 11 Members subjected to axial force with bending.. 15 Bearings. 19 6. Estimated lengths and ultimate flexibility of steel structure elements. 19 Estimated lengths of elements of flat trusses and connections. 19 Estimated lengths of elements of spatial lattice structures. 21 Estimated lengths of elements of structural structures. 23 Estimated lengths of columns (pillars) 23 Ultimate flexibility of compressed elements. 25 Ultimate flexibility of tension elements. 25 7. Checking the stability of the walls and waist sheets of bending and compressed elements. 26 Beam webs. 26 Walls of centrally eccentrically compressed and compressed-bent elements. 32 Belt sheets (shelves) of centrally-, eccentrically-compressed, compressed-bent and bent elements. 34 8. Calculation of sheet structures. 35 Strength calculation. 35 Calculation for sustainability. 37 Basic requirements for the calculation of metal membrane structures. 39 9. Calculation of elements of steel structures for endurance. 39 10. Calculation of elements of steel structures for strength, taking into account brittle fracture. 40 11. Calculation of connections of steel structures. 40 Welded joints. 40 Bolted connections. 42 Connections on high-strength bolts. 43 Connections with milled ends. 44 Belt connections in composite beams. 44 12. General requirements for the design of steel structures. 45 Fundamentals. 45 Welded joints. 46 Bolted connections and connections on high-strength bolts. 46 13. Additional requirements for the design of industrial buildings and structures. 48 Relative deflections and deviations of structures. 48 Distances between expansion joints. 48 Trusses and structural slabs. 48 Columns.. 49 Connections. 49 Beams. 49 Crane beams. 50 Sheet structures. 51 Mounting fasteners. 52 14. Additional requirements for the design of residential and public buildings and structures. 52 Frame buildings. 52 Hanging covers. 52 15*. Additional requirements for the design of supports for overhead power lines, structures of open switchgear and lines of contact networks of transport. 53 16. Additional requirements for the design of structures of antenna structures (ac) for communication up to 500 m high. . 55 17. Additional requirements for the design of river hydraulic structures. 58 18. Additional requirements for the design of beams with a flexible web. 59 19. Additional requirements for the design of beams with perforated web. 60 20*. Additional requirements for the design of structures of buildings and structures during reconstruction. 61 Appendix 1. Materials for steel structures and their design resistances. 64 Appendix 2. Materials for joints of steel structures and their design resistances. 68 Appendix 3. Physical characteristics of materials. 71 Appendix 4*. Service factors for a stretched single angle bolted on by a single flange. 72 Appendix 5. Coefficients for calculating the strength of steel structure elements, taking into account the development of plastic deformations. 72 Appendix 6. Coefficients for calculating the stability of centrally-, eccentrically-compressed and compressed-bent elements. 73 Appendix 7*. Odds φb for calculating beams for stability. 82 Appendix 8. Tables for calculating elements for endurance and taking into account brittle fracture. 85 Appendix 8, a. Determination of metal properties. 88 Appendix 9*. Basic letter designations of quantities. 89

The West-Siberian Metallurgical Plant has mastered the production of shaped steel (equal-shelf angles, channels, I-beams) with a flange thickness of up to 10 mm inclusive according to TU 14-11-302-94 “Shaped steel C345 from carbon steel modified with niobium”, developed by the plant, JSC “ Ural Institute of Metals” and approved by TsNIISK named after A.I. Kucherenko.

Glavtekhnormirovaniye informs that shaped steel from S345 steel of categories 1 and 3 according to TU 14-11-302-94 can be used in accordance with SNiP II-23-81 "Steel structures" (Table 50) in the same structures for which rolled products from steel С345 of categories 1 and 3 in accordance with GOST 27772-88.

Head of Glavtechnormirovaniya V.V. Tishchenko

Introduction

The metallurgical industry has mastered the production of rolled products for building steel structures and economically alloyed steel C315. Hardening, as a rule, is achieved by microalloying low-carbon calm steel with any of the elements: titanium, niobium, vanadium, or nitrides. Alloying can be combined with controlled rolling or heat treatment.

The achieved volumes of production of sheets and shaped profiles from the new C315 steel make it possible to fully satisfy the needs of construction in rolled products with strength characteristics and cold resistance close to the standards for low-alloy steel according to GOST 27772-88.

1. Normative documentation for rental

At present, a series of specifications for rolled products from steel C315 has been developed.

TU 14-102-132-92 "Rolled shaped steel S315". The holder of the original and the manufacturer of rolled products are the Nizhny Tagil Iron and Steel Works, the assortment is channel bars according to GOST 8240, equal-shelf angle profiles, unequal-shelf angle profiles, ordinary I-beams and with parallel flange edges.

TU 14-1-5140-92 “Rolled products for building steel structures. General technical conditions". The holder of the original is TSNIICHM, the manufacturer of rolled products is the Nizhny Tagil Iron and Steel Works, the assortment is I-beams according to GOST 26020, TU 14-2-427-80.

TU 14-104-133-92 "High-strength rolled products for building steel structures". The holder of the original and the manufacturer of the rolled products is the Orsk-Khalilovsky Metallurgical Plant, the assortment is a sheet with a thickness of 6 to 50 mm.

TU 14-1-5143-92 "Rolled sheet and coil products with increased strength and cold resistance". The holder of the original is TSNIICHM, the manufacturer of rolled products is the Novo-Lipetsk Iron and Steel Works, the assortment is rolled sheets according to GOST 19903 with a thickness of up to 14 mm inclusive.

TU 14-105-554-92 "Sheet products of increased strength and cold resistance". The holder of the original and the manufacturer of the rolled products are the Cherepovets Metallurgical Plant, the assortment is rolled sheets according to GOST 19903 with a thickness of up to 12 mm inclusive.

2. General provisions

2.1. Rolled steel C315 is advisable to use instead of rolled steel from low-carbon steel C255, C285 according to GOST 27772-88 for groups of structures according to SNiP II-23-8I, the use of which in climatic areas of construction with a design temperature of minus 40 ° C is not allowed. In this case, it is necessary to use the increased strength of rolled steel C315.

3. Materials for structures

3.1. Rolled steel S315 is supplied in four categories depending on the requirements for impact bending tests (categories are taken the same with rolled steel S345 according to GOST 27772-88).

3.2. Rolled steel C315 can be used in structures, guided by the data in Table. one.

Table 1

* With a rolled thickness of not more than 10 mm.

4. Design characteristics of rolled products and joints

4.1. Regulatory and design resistances of rolled steel C315 are taken in accordance with Table. 2.

table 2

Rolled thickness, mm	Normative resistance of rolled products, MPa (kgf / mm 2)	Design resistance of rolled products, MPa (kgf / mm 2)
	shaped	sheet, broadband universal	shaped
Ryn	Run	Ryn	Run	Ry	R u	Ry	R u
2-10	315 (32)	440 (45)	315 (32)	440 (45)	305 (3100)	430 (4400)	305 (3100)	430 (4400)
10-20	295 (30)	420 (43)	295 (30)	420 (43)	290 (2950)	410 (4200)	290 (2950)	410 (4200)
20-40	275 (28)	410 (42)	275 (28)	410 (42)	270 (2750)	400 (4100)	270 (2750)	400 (4100)
40-60	255 (26)	400 (41)	-	-	250 (2550)	390 (4000)	-	-

4.2. The design resistance of welded joints of rolled steel C315 for various types of joints and stressed joints should be determined according to SNiP II-23-81 * (clause 3.4, table 3).

4.3. The design resistance to collapse of elements connected by bolts should be determined according to SNiP II-23-81* (clause 3.5, table 5*).

5. Calculation of connections

5.1. Calculation of welded and bolted joints of rolled steel S315 is carried out in accordance with the requirements of SNiP II-23-81.

6. Fabrication of structures

6.1. In the manufacture of building structures from steel C315, the same technology should be used as for steel C255 and C285 according to GOST 27772-88.

6.2. Materials for welding rolled steel C315 should be taken in accordance with the requirements of SNiP II-23-81 * (Table 55 *) for rolled steel C255, C285 and C345 - according to GOST 27772-88, taking into account the design resistance of rolled steel C315 for different thicknesses .

On the use in the construction of high-strength plate rolled products according to TU 14-104-133-92

The Ministry of Construction of Russia sent a letter No. 13-227 dated November 11, 1992 to the ministries and departments of the Russian Federation, state construction of the republics within the Russian Federation, design and research institutes with the following content.

The Orsk-Khalilovsky Metallurgical Plant has mastered the production of thick-plate rolled products with a thickness of 6-50 mm according to the specifications of TU 14-104-133-92 "High-strength rolled products for building steel structures", developed by the plant, ITMT TsNIIchermet and TsNIISK them. Kucherenko.

Due to microalloying of low-carbon calm steel with titanium or vanadium (or both) with the possible use of heat treatment and controlled rolling modes, the plant obtained a new highly efficient type of rolled metal from steels S315 and S345E, the properties of which are not inferior to those of rolled products from low-alloy steels according to GOST 27772-88 . The method of microalloying, the type of heat treatment and rolling conditions are chosen by the manufacturer. Rolled products are supplied in four categories depending on the impact test requirements adopted in GOST 27772-88 and SNiP II-23-81*, as well as in the German standard DIN 17100 (on samples with a sharp notch). The category and type of impact bending test is indicated by the consumer in the order for rolled metal products.

The Ministry of Construction of Russia informs that rolled steel S345E according to TU 14-104-133-92 can be used along with and instead of rolled steel S345 according to GOST 27772-88 in structures designed according to SNiP II-23-81 * "Steel structures", without recalculation of sections of elements and their connections. The scope, normative and design resistance of rolled steel S315 according to TU 14-104-133-92, as well as the materials used for welding, design resistance of welded joints and collapse of elements connected by bolts, should be taken according to the recommendations of TsNIISK im. Kucherenko, published below.

The Nizhny Tagil Iron and Steel Works has mastered the production of shaped steel - channels according to GOST 8240, angles according to GOST 8509 and GOST 8510, I-beams according to GOST 8239, GOST 19425, TU 14-2-427-80, wide flange I-beams according to GOST 26020 according to specifications TU 14-1 -5140-82 "Rolled shaped increased strength for building steel structures", developed by the plant, TsNIIchermet them. Bardin and TsNIISK them. Kucherenko.

Due to the rational selection of the chemical composition of low-carbon steel, microalloying and saturation of it with nitrides and carbonitrides with grain refinement during the rolling process, the plant obtained a highly efficient type of rolled products from steels C315, C345 and C375, the properties of which are not inferior to those of rolled products from low-alloy steels according to GOST 27772.

Rolled products are supplied in four categories depending on the impact test requirements adopted in GOST 27772-88 and SNiP II-23-81*, as well as in the German standard DIN 17100 (on samples with a sharp notch). The category and type of impact bending test is indicated by the consumer in the order for rolled metal products.

Gosstroy of Russia informs that rolled products from steel S345 and S375 according to TU 14-1-5140-92 can be used along with and instead of rolled steel from steel S345 and S375 according to GOST 27772-88 in structures designed according to SNiP II-23-81 * "Steel structures”, without recalculation of the sections of elements and their connections. The scope, normative and design resistances of rolled steel S315 according to TU 14-1-3140-92, as well as the materials used for welding, design resistances of welded joints, crushing of elements connected by bolts, should be taken according to the “Recommendations” of TsNIISK them. Kucherenko, which were published in the Bulletin of Construction Equipment No. 1, 1993.

Deputy Chairman V.A. Alekseev

Use Poddubny V.P.

GENERAL PROVISIONS

1.1. These standards should 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 of 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, tanks for special purposes, structures of buildings subjected to seismic, intense temperature effects or 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 should be observed that reflect the features of the operation of these structures, provided for by the relevant regulatory documents approved or agreed by the Gosstroy of the USSR.

1.2. When designing steel structures, the norms of SNiP for the protection of building structures against corrosion and fire safety standards for the design of buildings and structures should be observed. An increase in 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 and hinder ventilation. Closed profiles must be sealed.

1.3*. When designing steel structures, you should:

choose the optimal schemes of structures and sections of elements in technical and economic terms;

apply economical rolled profiles and efficient steels;

apply for buildings and structures, as a rule, unified standard or standard designs;

apply progressive structures (spatial systems of standard elements; structures that combine load-bearing and enclosing functions; prestressed, cable-stayed, thin-sheet and combined structures made of different steels);

provide for the manufacturability of the manufacture and installation of structures;

apply designs that ensure the least laboriousness of their manufacture, transportation and installation;

provide, as a rule, in-line production of structures and their conveyor or large-block installation;

provide for the use of factory connections of progressive types (automatic and semi-automatic welding, flange connections, with milled ends, on bolts, including high-strength ones, etc.);

provide, as a rule, mounting connections on bolts, including high-strength ones; welded field 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 the working (KM) and detailing (KMD) drawings of steel structures and in the documentation for ordering materials.

Depending on the features of the structures and their components, it is necessary to indicate the continuity class in accordance with GOST 27772-88 when ordering steel.

1.6*. Steel structures and their calculation must meet the requirements of GOST 27751-88 “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 the calculation.

1.7. Design schemes and the basic prerequisites for the calculation should reflect the actual operating conditions of steel structures.

Steel structures should, as a rule, be calculated as single spatial systems.

When dividing unified spatial systems into separate flat structures, one should take into account the interaction of elements with each other and with the base.

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. The design of steel structures should, as a rule, be performed 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 is allowed to be carried out according to a deformed scheme, taking into account the effect of movements of structures under load.

1.9. Elements of steel structures must have minimum sections that meet the requirements of these standards, taking into account the assortment for rolled products and pipes. In the composite sections established by calculation, the understress should not exceed 5%.

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4.1. The calculation of centrally tensioned elements should be carried out according to the formula

where N is the calculated longitudinal force;

R p is the calculated tensile strength of wood along the fibers;

F nt is the net cross-sectional area of the element.

When determining F Attenuation points located in a section up to 200 mm long should be taken combined in one section.

4.2. The calculation of centrally compressed elements of a constant solid section should be made according to the formulas:

a) strength

b) stability

where R c - design resistance of wood to compression along the fibers;

j is the buckling coefficient determined in accordance with clause 4.3;

F nt is the net cross-sectional area of the element;

F race - the calculated cross-sectional area of the element, taken equal to:

in the absence of weakening or weakening in dangerous sections that do not extend to the edges (Fig. 1, a), if the attenuation area does not exceed 25% E br, E calc = F br where F br - gross sectional area; for weakenings that do not extend to the edges, if the weakening area exceeds 25% F br, F races = 4/3 F nt; with symmetrical weakening that goes to the edges (Fig. 1, b), F races = F nt.

4.3. Buckling coefficient j should be determined by formulas (7) and (8);

with element flexibility l £ 70

; (7)

with element flexibility l > 70

where coefficient a = 0.8 for wood and a = 1 for plywood;

coefficient A = 3000 for wood and A = 2500 for plywood.

4.4. The flexibility of solid section elements is determined by the formula

where l o is the estimated length of the element;

r is the radius of gyration of the section of the element with the maximum gross dimensions, respectively, relative to the axes X and At.

4.5. Estimated element length l o should be determined by multiplying its free length l by the coefficient m 0

l o= l m 0 (10)

according to paragraphs. 4.21 and 6.25.

4.6. Composite elements on compliant joints, supported by the entire cross section, should be calculated for strength and stability according to formulas (5) and (6), while F nt and F races are defined as the total areas of all branches. The flexibility of the constituent elements l should be determined taking into account the compliance of the joints according to the formula

, (11)

where l y is the flexibility of the entire element relative to the axis At(Fig. 2), calculated from the estimated length of the element l o excluding compliance;

l 1 is the flexibility of a separate branch relative to the I–I axis (see Fig. 2), calculated from the estimated length of the branch l one ; at l 1 less than seven thicknesses ( h 1) branches are accepted l 1 = 0;

m y is the coefficient of reduction of flexibility, determined by the formula

, (12)

where b and h- width and height of the cross section of the element, cm:

n w is the calculated number of seams in the element, determined by the number of seams over which the mutual shift of the elements is summed up (in Fig. 2, a- 4 seams, in fig. 2, b- 5 stitches);

l o is the estimated length of the element, m;

n c - the estimated number of cuts of bonds in one seam per 1 m of the element (for several seams with a different number of cuts, the average number of cuts for all seams should be taken);

k c is the coefficient of ductility of the joints, which should be determined by the formulas of Table. 12.

Table 12

Note. Diameters of nails and dowels d, element thickness a, width b pl and thickness d of plate dowels should be taken in cm.

When determining k with the diameter of the nails should be taken no more than 0.1 of the thickness of the connected elements. If the size of pinched nail ends is less than 4 d, then the sections in the seams adjacent to them are not taken into account in the calculation. Meaning k from joints on steel cylindrical dowels should be determined by thickness a thinner of the connected elements.

When determining k with a diameter of oak cylindrical dowels, no more than 0.25 of the thickness of the thinner of the connected elements should be taken.

Ties in the seams should be spaced evenly along the length of the element. In hinged-supported rectilinear elements, it is allowed to put connections in the middle quarters of the length in half the amount, introducing into the calculation according to the formula (12) the value n s, adopted for the extreme quarters of the length of the element.

The flexibility of a composite element, calculated by formula (11), should be taken no more than the flexibility of l individual branches, determined by the formula

, (13)

where e I i br is the sum of the gross moments of inertia of the cross sections of individual branches relative to their own axes parallel to the axis At(see Fig. 2);

F br is the gross sectional area of the element;

l o is the estimated length of the element.

The flexibility of a composite element with respect to the axis passing through the centers of gravity of the sections of all branches (the axis X in fig. 2), should be determined as for a solid element, i.e., without taking into account the compliance of the bonds, if the branches are loaded evenly. In the case of unevenly loaded branches, paragraph 4.7 should be followed.

If the branches of the composite element have a different cross section, then the calculated flexibility l 1 of the branch in formula (11) should be taken equal to:

, (14)

definition l 1 is shown in fig. 2.

a) the cross-sectional area of the element F nt and F races should be determined by the cross section of supported branches;

b) the flexibility of the element relative to the axis At(see Fig. 2) is determined by formula (11); in this case, the moment of inertia is taken taking into account all branches, and the area is taken into account only supported ones;

c) when determining flexibility relative to the axis X(see Fig. 2) the moment of inertia should be determined by the formula

I = I o + 0.5 I but, (15)

where I oh and I but are the moments of inertia of the cross sections of the supported and unsupported branches, respectively.

4.8. The calculation for the stability of centrally compressed elements of a section with a variable height should be performed according to the formula

, (16)

where F max - gross cross-sectional area with maximum dimensions;

k and N- coefficient taking into account the variability of the section height, determined from Table. 1 app. 4 (for elements of constant section k and N = 1);

j is the buckling coefficient determined according to clause 4.3 for the flexibility corresponding to the section with the maximum dimensions.

Bending elements

4.9. Calculation of bending elements, secured against buckling of the flat form of deformation (see paragraphs 4.14 and 4.15), for strength under normal stresses should be carried out according to the formula

where M- calculated bending moment;

R and - design resistance to bending;

W ras - the calculated moment of resistance of the cross section of the element. For solid elements W races = W nt; for bending components on flexible joints, the design modulus should be taken equal to the net modulus W nt multiplied by the coefficient k w values k w for elements composed of identical layers are given in table. 13. When determining W NT weakening of the sections, located on the section of the element with a length of up to 200 mm, is taken combined in one section.

Table 13

Coefficient designation	Number of layers	The value of the coefficients for the calculation of bending components during spans, m
agents	in element				9 or more
		0,7	0,85	0,9	0,9
k w		0,6	0,8	0,85	0,9
		0,4	0,7	0,8	0,85
		0,45	0,65	0,75	0,8
k and		0,25	0,5	0,6	0,7
		0,07	0,2	0,3	0,4

Note. For intermediate values of the span and the number of layers, the coefficients are determined by interpolation.

4.10. Calculation of bending elements for shearing strength should be performed according to the formula

where Q- design transverse force;

S br is the gross static moment of the shifted part of the cross section of the element relative to the neutral axis;

I br is the gross moment of inertia of the cross section of the element relative to the neutral axis;

b ras - the calculated width of the section of the element;

R sk is the design resistance to shearing in bending.

4.11. Number of link slices n s, evenly spaced in each seam of a composite element in a section with an unambiguous diagram of transverse forces, must satisfy the condition

, (19)

where T- the calculated bearing capacity of the connection in this seam;

M BUT, M B - bending moments in the initial A and final B sections of the section under consideration.

Note. If there are bonds of different bearing capacity in the seam, but identical in nature of work (for example, dowels and nails), their bearing capacities should be summed up.

4.12. The calculation of elements of a solid section for strength in oblique bending should be carried out according to the formula

, (20)

where M x and M y - components of the calculated bending moment for the main axes of the section X and At;

W x and W y - net section modulus relative to the main axes of the section X and At.

4.13. Glued curved elements subject to moment bending M, which reduces their curvature, should be checked for radial tensile stresses according to the formula

, (21)

where s 0 is the normal stress in the outermost fiber of the stretched zone;

s i is the normal stress in the intermediate fiber of the section for which the radial tensile stresses are determined;

h i is the distance between the extreme and considered fibers;

r i is the radius of curvature of the line passing through the center of gravity of the part of the diagram of normal tensile stresses, enclosed between the extreme and considered fibers;

R p.90 - the calculated resistance of wood to stretching across the fibers, taken according to clause 7 of the table. 3.

4.14. Calculation for the stability of a flat form of deformation of bent elements of a rectangular constant section should be carried out according to the formula

where M- the maximum bending moment in the area under consideration l R;

W br is the maximum gross moment of resistance in the area under consideration l p .

The coefficient j M for bending elements of a rectangular constant cross section, hinged against displacement from the bending plane and fixed against rotation around the longitudinal axis in the reference sections, should be determined by the formula

, (23)

where l p is the distance between the support sections of the element, and when fixing the compressed edge of the element at intermediate points from displacement from the bending plane, the distance between these points;

b is the width of the cross section;

h- the maximum height of the cross section on the site l p;

k f - coefficient depending on the shape of the diagram of bending moments in the section l p , determined from the table. 2 app. 4 of these rules.

When calculating bending elements with a height linearly changing along the length and a constant width of the cross section, which do not have fastenings from the plane along the stretched from the moment M edge, or m < 4 коэффициент jM according to formula (23) should be multiplied by an additional coefficient k and M. Values k and M are given in table. 2 app. 4. When m³ 4 k and M = 1.

When reinforcing from the bending plane at intermediate points of the stretched edge of the element in the section l p coefficient j M determined by formula (23), should be multiplied by the coefficient k P M :

, (24)

where a p is the central angle in radians defining the area l p element of circular shape (for rectilinear elements a p = 0);

m- the number of reinforced (with the same step) points of the stretched edge on the section l p (when m³ 4, the value should be taken equal to 1).

4.15. Checking the stability of the flat form of deformation of bending elements of a constant I-beam or box-shaped cross-section should be carried out in cases where

l p ³ 7 b, (25)

where b is the width of the compressed belt of the cross section.

The calculation should be made according to the formula

where j is the coefficient of buckling from the bending plane of the compressed chord of the element, determined according to clause 4.3;

R c is the calculated compressive strength;

W br is the moment of resistance of the gross cross-section; in the case of plywood walls, the reduced modulus of resistance in the bending plane of the element.

Initially, metal, as the most durable material, served protective purposes - fences, gates, gratings. Then they began to use cast-iron poles and arches. The expanded growth of industrial production required the construction of structures with large spans, which stimulated the appearance of rolled beams and trusses. As a result, the metal frame became a key factor in the development of the architectural form, as it allowed the walls to be freed from the function of the supporting structure.

Central tension and central compression steel elements. Calculation of the strength of elements subject to central tension or compression by force N, should be done according to the formula

where is the calculated resistance of steel to tension, compression, bending in terms of yield strength; is the net cross-sectional area, i.e. area minus the weakening of the section; - coefficient of working conditions, taken according to the tables of SNIP N-23-81 * "Steel structures".

Example 3.1. A hole with a diameter of d= = 10 cm (Fig. 3.7). I-beam wall thickness - s- 5.2 mm, gross cross-sectional area - cm2.

It is required to determine the allowable load that can be applied along the longitudinal axis of the weakened I-beam. The design resistance began to take kg / cm2, and.

Solution

We calculate the net cross-sectional area:

where is the gross sectional area, i.e. the total cross-sectional area, excluding weakening, is taken in accordance with GOST 8239–89 "Hot-rolled steel I-beams".

Determine the allowable load:

Determining the absolute elongation of a centrally tensioned steel bar

For a bar with a stepwise change in cross-sectional area and normal force, the total elongation is calculated by algebraic summation of the elongations of each section:

where P - number of plots; i- lot number (i = 1, 2,..., P).

The elongation from the own weight of a rod of constant section is determined by the formula

where γ is the specific gravity of the rod material.

Sustainability calculation

Calculation for the stability of solid-walled elements subject to central compression by force N, should be performed according to the formula

where A is the gross sectional area; φ - coefficient of buckling, taken depending on the flexibility

Rice. 3.7.

and design resistance of steel according to the table in SNIP N-23–81 * "Steel structures"; μ is the length reduction factor; – minimum radius of gyration cross section; Flexibility λ of compressed or tensioned elements should not exceed the values given in SNIP "Steel structures".

The calculation of composite elements from angles, channels (Fig. 3.8), etc., connected closely or through gaskets, should be performed as solid-walled, provided that the largest clear distances in the areas between the welded strips or between the centers of the extreme bolts do not exceed for compressed elements and for stretched elements.

Rice. 3.8.

Bending steel elements

The calculation of beams bent in one of the main planes is performed according to the formula

where M - maximum bending moment; is the net section modulus.

The values of shear stresses τ in the middle of the bending elements must satisfy the condition

where Q- transverse force in section; - static moment of half the section relative to the main axis z;- axial moment of inertia; t– wall thickness; – design shear resistance of steel; - the yield strength of steel, adopted according to state standards and specifications for steel; - reliability factor for the material, adopted according to SNIP 11-23-81 * "Steel structures".

Example 3.2. It is required to select the cross section of a single-span steel beam loaded with a uniformly distributed load q= 16 kN/m, can length l= 4 m, , MPa. The cross section of the beam is rectangular with a height ratio h to width b beams equal to 3 ( h/b = 3).