Cross sequence area. Calculation of the steel column
Calculation of elements of wooden structuresaccording to the limit states of the first group
Centrally stretched and centrally compressed elements
6.1 Calcentally stretched elements should be made by the formula
where is the estimated longitudinal force;
Estimated wood resistance to stretching along the fibers;
The same, for wood from unidirectional veneer (5.7);
The cross-sectional area of \u200b\u200bthe net element.
When determining the attenuation, located on a plot of up to 200 mm long, one should be taken in one cross section.
6.2 Calcative solo-compressed electroplated solid section surrenders by formulas:
a) for strength
b) on stability
where - the calculated resistance of wood compression along the fibers;
The same, for wood from unidirectional veneer;
The coefficient of longitudinal bending, determined according to 6.3;
Nette-cross section area of \u200b\u200bthe element;
The estimated cross-sectional area of \u200b\u200bthe element, taken equal:
in the absence of weakens or weakens in hazardous sections that do not leave on the edges (Figure 1, but) if the area of \u200b\u200bweakens does not exceed 25%, where- the cross section of gross; with weakens not emerging on the edges if the area of \u200b\u200bweakening exceeds 25%; with symmetric weakens overlooking the edges (Figure 1, b.),.
but- not leaving on the edge; b.- emerging to the edge
Picture 1- weakening compressed elements
6.3 The coefficient of longitudinal will bended to determine by formulas:
with the flexibility of the element 70
with the flexibility of the element 70
where the coefficient is 0.8 for wood and1.0 for plywood;
the coefficient 3000 for wood and 2500 for plywood and wood from a unidirectional veneer.
6.4 The flexibility of solid section elements is determined by the formula
where - the estimated length of the element;
The radius of the inertia section of the element with the maximum gross dimensions relative to the axis.
6.5 The estimated length of elementary lines to determine the multiplication of its free length coefficient
according to 6.21.
6.6 Composite elements on pliable compounds, opened by the entire cross section, should be calculated on strength and stability according to formulas (8) and (9), with this detecting as the total area of \u200b\u200ball branches. Flexibility of composite elementaries to determine taking into account the compounds of the compounds by the formula
where - the flexibility of the entire element relative to the axis (Figure 2), calculated at the estimated length of the elementalization of adhesiveness;
* - the flexibility of the individual branch relative to the I - I axis (see Figure 2), calculated according to the calculated length of the branch; The more seven thicknesses () branches are accepted by C0 *;
The coefficient of bringing the flexibility determined by the formula
* Formula and explication to it correspond to the original. - Note database manufacturer.
where the width and height of the cross section of the element, see;
The calculated number of seams in the element determined by the number of seams, according to which the mutual shift of the elements is cashed (in Figure 2, but- 4 seam, in Figure 2, b.- 5 seams);
The estimated length of the element, m;
The calculated number of sections of links in one seam per 1 m of the element (with several seams with a different number of sections, the number of sections should be taken between all seams);
The coefficient of the compounds that should be determined by the formulas of the table 15.
but- with gaskets, b.- without pads
Figure 2.- Composite elements
Table 15.
|
Type of connencence |
The coefficient is |
|
|
central compression |
compression with bend |
|
|
1 nails, screws | ||
|
2 steel cylindrical brazen | ||
|
a) the thickness diameter of the connected elements | ||
|
b) the thickness diameter of the connected elements | ||
|
3 Intended rods from A240-A500 reinforcement | ||
|
4 oak cylindrical brazening | ||
|
5 oak lamellar brazen | ||
|
Note - Diameters of nails, screws, brazen and pasted rods, the thickness of the elements, the width of the thickness of the thicknesses should be taken in cm. |
||
When determining the diameter of nails, no more than 0.1 thickness of the connected elements should be taken. If the size of the attacked ends of nails is less, then the sections in the seams adjacent to them do not take into account. Exceptions on steel cylindrical impulses should be determined by the thickness of the most thin of the connected elements.
When determining the diameter of oak cylindrical copiers, no more than 0.25 thickness of the thinner of the connected elements should be taken.
Communication in the seams should be uniformly on the length of the element. In hinged-opened straight elements, it is allowed in the average quarters of the length of the length of communication in half quantities, in charge of the formula (12), the amount accepted for the extreme quarters of the length of the element.
The flexibility of the component element calculated by formula (11) should be taken no more than the flexibility of the individual branches determined by the formula:
where - the sum of the moments of the inertia of the gross cross sections of the individual branches relative to their own axes parallel to OCI (see Figure 2);
Cross section of the gross element;
The calculated length of the element.
The flexibility of the component element relative to the axis passing through the severity centers of all branches (axis in Figure 2) should be determined as for a one-piece element, i.e. Without taking into account the advantage of links, if the branches are loaded uniformly. In the case of uneven loaded branches, 6.7 should be guided.
If the branches of the component element have a different section, then the calculated flexibility of the branch in formula (11) should be taken equal
the definition is shown in Figure 2.
6.7 Composite elements on fuel connections, part of the branches of which are not operated at the ends, is allowed to calculate for strength and stability by formulas (5), (6) subject to the following conditions:
a) the cross-sectional area of \u200b\u200bthe element will be determined by the cross section of the opened branches;
b) the flexibility of the element relative to the axis (see Figure 2) is determined by formula (11); At the same time, the moment of inertia is adopted taking into account all the branches, and the area is only opened;
c) when determining flexibility relative to the axis (see Figure 2) the moment of inertia should be determined by the formula
where the moments of the inertia of the cross sections, respectively, the support and underdeveloped branches.
6.8 The calculation on the stability of the central-compressed elements of the variable in the height of the section should be performed by the formula
where - the cross-sectional area of \u200b\u200bgross with maximum dimensions;
Coefficient that takes into account the height variability of the section, determined by Table E.1 of Appendix E (for the elements of constant section1);
The coefficient of longitudinal bending, determined by 6.3 for flexibility corresponding to the cross section with the maximum dimensions.
4.1. Calculation of centrally stretched elements should be made by the formula
where N. - estimated longitudinal force;
R. P is the calculated wood resistance to stretching along the fibers;
F. NT - cross-sectional area of \u200b\u200bnet element.
When determining F. NT attenuation, located on a plot of up to 200 mm long, should be made in one section combined.
4.2. The calculation of the central-compressed elements of a permanent one-piece section should be made by formulas:
a) for strength
b) on stability
where R. C - calculated wood resistance to compression along the fibers;
j - the coefficient of longitudinal bending, determined in accordance with clause 4.3;
F. NT - net cross section of the element;
F. RAC - the calculated cross-sectional area of \u200b\u200bthe element taken equal:
in the absence of weakens or weakens in hazardous sections that do not leave on the edges (Fig. 1, but) if the area of \u200b\u200bweakens does not exceed 25% E. BR, E. calc \u003d F. Br, where F. Br - Cross cross section area; With weakens not leaving on the edges, if the area of \u200b\u200bweakening exceeds 25% F. BR, F. RAC \u003d 4/3. F. NT; with symmetric weakens overlooking the edges (Fig. 1, b.), F. Ras \u003d F. NT.
4.3. The longitudinal bend coefficient J should be determined by formulas (7) and (8);
with the flexibility of the element l £ 70
; (7)
with the flexibility of the element L\u003e 70
where is the coefficient a \u003d 0.8 for wood and a \u003d 1 for plywood;
the coefficient A \u003d 3000 for wood and a \u003d 2500 for plywood.
4.4. The flexibility of solid section elements is determined by the formula
where l. o - estimated length of the element;
r. - radius of inertia cross sections of the element with the maximum size of gross, respectively, relative to the axes H. and W..
4.5. Calculated length of element l. oh should determine the multiplication of its free length l. on the coefficient M 0
l. Oh \u003d. l.m 0 (10)
according to PP. 4.21 and 6.25.
4.6. Composite elements on pliable compounds, opened by all cross section, should be calculated on strength and stability according to formulas (5) and (6), while F. NT I. F. Rasually define as the total area of \u200b\u200ball branches. The flexibility of the component elements L should be determined taking into account the compounds of the compounds by the formula
, (11)
where L y is the flexibility of the entire element relative to the axis W. (Fig. 2) calculated by the estimated length of the element l. o without taking advantage;
l 1 - flexibility of a separate branch relative to the I - I axis (see Fig. 2), calculated in the calculated length of the branch l. one ; for l. 1 less than seven thicknesses ( h. 1) branches are accepted by l 1 \u003d 0;
m y - coefficient of flexibility determined by the formula
, (12)
where b. and h. - width and height of the cross section of the element, see:
n. W - the calculated amount of seams in the element determined by the number of seams, according to which the mutual shift of the elements is summed (in Fig. 2, but - 4 seam, in fig. 2, b. - 5 seams);
l. o - estimated length of the element, m;
n. C - the calculated number of sections of links in one seam per 1 m of the element (with several seams with a different number of slices, the number of slices should be taken between all seams);
k. C - the coefficient of the compounds, which should be determined by the formulas of the table. 12.
Table 12.
Note. Diameters of nails and copily d., thickness elements but, width B. Ploves and thickness D of lamellar copiers should be taken in cm.
When determining k. With the diameter of nails, no more than 0.1 thickness of the connected elements should be taken. If the size of the pinched ends of the nails is less than 4 d., Cuts in the seams adjacent to them do not take into account. Value k. From compounds on steel cylindrical impudations should be determined by thickness but Thinner of the connected elements.
When determining k. With the diameter of oak cylindrical copiers, no more than 0.25 thickness of the thinner of the connected elements should be taken.
Communication in the seams should be uniformly on the length of the element. In hinged-opened straightforward elements, it is allowed in the middle quarters of the length of the length of communication in half quantities, in charge of the formula (12) value n. with, accepted for extreme quarters of the length of the element.
The flexibility of the compound element calculated by formula (11) should be taken no more than the flexibility of L of individual branches determined by the formula
, (13)
where Å. I I. BR - sum of the moments of inertia gross cross sections of individual branches relative to their own axes parallel to the axis W. (see Fig. 2);
F. BR - cross section of the gross element;
l. O is the estimated length of the element.
The flexibility of the component element relative to the axis passing through the centers of severity of the sections of all branches (axis H. In fig. 2), it should be determined as for a one-piece element, that is, without taking into account the advantage of bonds, if the branches are loaded evenly. In the case of uneven loaded branches, paragraph 4.7 should be guided.
If the branches of the compound element have a different section, then the estimated flexibility of L 1 branches in formula (11) should be taken equal to:
, (14)
definition l. 1 is shown in Fig. 2.
4.7. Composite elements on fuel connections, part of the branches of which are not operated at the ends, is allowed to calculate for strength and stability by formulas (5), (6) subject to the following conditions:
a) cross-sectional area element F. NT I. F. races should be determined by the cross section of the opened branches;
b) the flexibility of the element relative to the axis W. (see Fig. 2) is determined by formula (11); At the same time, the moment of inertia is adopted taking into account all the branches, and the area is only opened;
c) when determining flexibility relative to the axis H. (see Fig. 2) The moment of inertia should be determined by the formula
I. = I. O + 0.5. I. But, (15)
where I. About I. I. But the moments of the inertia of the cross sections, respectively, the support and underdeveloped branches.
4.8. The calculation on the stability of the central-compressed elements of the variable in the height of the section should be performed by the formula
, (16)
where F. Max - Cross cross section area with maximum dimensions;
k. J. N. - coefficient, taking into account the altitude of the section, determined by table. 1 arr. 4 (for constant sections k. J. N. = 1);
j is the coefficient of longitudinal bending, determined by clause 4.3 for flexibility corresponding to the cross section with the maximum dimensions.
Bend elements
4.9. Calculation of bending elements provided on the loss of stability of a flat deformation form (see paragraphs. 4.14 and 4.15), for strength on normal voltages should be made by the formula
where M. - Estimated bending moment;
R. and - the estimated resistance of bending;
W. RAC - the estimated moment of resistance of the cross section of the element. For one-piece elements W. Ras \u003d W. NT; For bending components on fuel connections, the estimated amount of resistance should be taken to an equal torque of the net resistance W. NT multiplied by the coefficient k. w; Values k. w for elements made up of the same layers are shown in Table. 13. When determining W. NT attenuation of sections, located on the element section of up to 200 mm long, is taken by combined in one section.
Table 13.
| The designation of the coefficient | Number of layers | The value of the coefficients for calculating the bent component elements in flights, m | |||
| Fitizients | 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. J. | 0,25 | 0,5 | 0,6 | 0,7 | |
| 0,07 | 0,2 | 0,3 | 0,4 |
Note. For intermediate values \u200b\u200bof the value of the span and the number of layers, the coefficients are determined by interpolation.
4.10. Calculation of bending elements on the durability of rocking should be carried out by the formula
where Q. - calculated transverse force;
S. Br - static moment of gross shift part of the cross section of the element relative to the neutral axis;
I. BR is the moment of inertia gross cross section of the element relative to the neutral axis;
b. calculation width of the section of the element;
R. SC - calculated resistance to the crevice during bending.
4.11. Number of sections of connections n. C, uniformly placed in each seam of the composite element on a plot with unambiguous line of transverse forces, must satisfy the condition
, (19)
where T. - the calculated carrying capacity of communication in this seam;
M. BUT, M. B - bending moments in the initial A and finite in the sections of the section under consideration.
Note. If there are connections in the seam of bonds of different bearing ability, but the same by the nature of the work (for example, aging and nails), the bearing abilities should be summed.
4.12. Calculation of elements of one piece for strength in oblique bending should be made by the formula
, (20)
where M. X I. M. y - components of the estimated bending moment for the main axes of section H. and W.;
W. X I. W. U - moments of the resistance of the cross section of the net relative to the main axes of section H. and W..
4.13. Glued curvilinear elements bends M.reducing their curvature, should be checked for radial tensile stresses by the formula
, (21)
where S 0 is a normal voltage in the extreme fiber stretched zone;
s. I. - normal voltage in the intermediate fiber section, for which radial tensile stresses are determined;
h I. - the distance between the extreme and considered fibers;
r I. - the radius of the curvature of the line passing through the center of gravity of the part of the plot of normal tensile stresses concluded between the extreme and considered fibers;
R. P.90 is the calculated wood resistance to stretching across the fibers taken according to clause 7 tab. 3.
4.14. Calculation of the stability of a flat form of deformation of bending elements of the rectangular constant section should be made by the formula
where M. - Maximum bending moment on the site under consideration l. R;
W. BR - the maximum moment of brutate resistance on the site under consideration l. p.
The coefficient J M for the bending elements of the rectangular constant cross section, hinged-fixed from the offset from the bending plane and fixed from rotation around the longitudinal axis in the support sections, should be determined by the formula
, (23)
where l. P is the distance between the supporting sections of the element, and when fixing the compressed edge of the element at intermediate points from the displacement from the bend plane - the distance between these points;
b. - the width of the cross section;
h. - Maximum height of the cross section on the site l. P;
k. F - coefficient depending on the shape of the fusion of bending moments on the site l. P, defined by table. 2 arr. 4 of these standards.
When calculating bending elements with a linearly changing in length of height and constant width of cross-section, not having fasteners from a plane stretched from moment M. edge, or when m. < 4 коэффициент j M. By formula (23) should be multiplied by an additional coefficient k. J. M. . Values k. J. M. Led in Table. 2 arr. 4. Ply m.³ 4. k. J. M. = 1.
When reinforcing from the bending plane at intermediate points of the stretched edge of the element on the site l. P The coefficient J. M. defined by formula (23), should be multiplied by the coefficient k. P M. :
, (24)
where a p is a central angle in radians determining the site l. p element of the circular outline (for straight elements a p \u003d 0);
m. - the number of reinforced (with the same step) points of the stretched edge on the site l. P (for m. ³ 4 The magnitude should be taken equal to 1).
4.15. Checking the stability of a flat form of deformation of the bending elements of a permanent dual-level or box cross sections should be made in cases where
l. P ³ 7. b., (25)
where b. - width of a compressed cross-sectional belt.
Calculation should be made by the formula
where j is the coefficient of longitudinal bending from the bending plane of the compressed belt of the element, defined by clause 4.3;
R. C - calculated compression resistance;
W. BR is the moment of brutate cross-section resistance; In the case of plywood walls - the present time of resistance in the bending plane of the element.
Initially, the metal as the most durable material served as protective goals - fences, gates, grilles. Then they began to use cast iron poles and arches. Advanced growth of industrial production required the construction of structures with large spans, which stimulated the appearance of rolling beams and farms. As a result, the metal frame has become a key factor in the development of architectural form, as it allowed to free the walls from the function of the supporting structure.
Central-stretched and centrally compressed steel elements. The calculation of the strength of elements subject to central stretching or compression by force N, should be performed by the formula
where - the calculated resistance has become stretching, compression, bending along the yield strength; - Net cross section area, i.e. The area minus the weakening of the section; - the coefficient of working conditions received by tables SNiP H-23-81 * "Steel structures".
Example 3.1. In the wall of the steel heateur number 20 cut the hole with a diameter d. \u003d \u003d 10 cm (Fig. 3.7). Wall thickness of the heap - s - 5.2 mm, cross-sectional area gross - cm2.
It is required to determine the allowable load, which can be applied along the longitudinal axis of the weakened duct. The calculated resistance began to take kg / cm2, and.
Decision
We calculate the area of \u200b\u200bthe Net cross section:
where is the cross section of gross, i.e. The area of \u200b\u200bthe total cross section is excluding the weakens, it is accepted according to GOST 8239-89 "Steel hot-rolled 2.
Determine the allowable load:
Determination of the absolute elongation of the central-stretched steel rod
For a rod with a stepped change in cross-sectional area and a normal force, the total lengthening is elongated by algebraic summation of the elongation of each site:
where p - number of sections; i. - Plot number (I \u003d. 1, 2,..., p).
The elongation of its own weight of the constant cross section is determined by the formula
where γ is the proportion of the material of the rod.
Calculation of stability
Calculation of the stability of solid-trimmed elements subject to central compression by force N.should be carried out by the formula
where a is the cross section of gross; φ - the coefficient of longitudinal bending taken depending on flexibility
Fig. 3.7.
and the design resistance of Stalipo Table in SNIP H-23-81 * "Steel Structures"; μ is the coefficient of bringing length; - minimal radius of inertia cross-section; The flexibility of λ compressed or stretched elements should not exceed the values \u200b\u200bshown in the "steel structures".
Calculation of composite elements from the corners, channels (Fig. 3.8), etc., connected closely or through gaskets, should be performed as soloshy, provided that the largest distance in the light on the sections between the welded planks or between the centers of the extreme bolts are not exceeded for compressed Elements and for stretched elements.
Fig. 3.8.
Bend steel elements
The calculation of bends in one of the main planes of beams is performed by the formula
where M - Maximum bending moment; - The moment of the resistance of the Net cross section.
The values \u200b\u200bof tangent stresses τ in the middle of the bending elements must satisfy the condition
where Q - transverse force in the cross section; - Static moment of half of the section relative to the main axis z; - axial moment of inertia; t. - wall thickness; - the calculated resistance has become a shift; - the yield strength of steel, adopted on state standards and technical conditions for steel; - The coefficient of reliability by material taken by SNIP 11-23-81 * "Steel structures".
Example 3.2. It is necessary to choose the cross section of a single-span steel beam loaded uniformly distributed load q. \u003d 16 kN / m, bank length l.\u003d 4 m,, MPa. The cross section of the beam is rectangular with a height attitude h. To width b. beams equal to 3 ( h / B \u003d 3).
BUT - Cross cross section area;
A BN. - Net bolt cross section;
A D. - section cross section;
A F. - cross section of the shelf (belt);
A N. - Net cross section area;
A W. - area cross section of the wall;
A WF. - cross-sectional area of \u200b\u200bthe corner seam;
A wz. - cross-sectional area of \u200b\u200bfusion border;
E. - elastic modulus;
F. - force;
G. - shift module;
J B -moment of inertia of the section of the branch;
J M.; J D. - moments of inertia cross sections of the belt and split farm;
J S. - the moment of inertia of the cross section of the rib, the planks;
J SL. - the moment of inertia section of the longitudinal rib;
J T. - the moment of inertia of the twisting beam, rail;
J X.; J y. - moments of inertia cross sections of gross relative to the axes, respectively x-X. and y-Y.;
J XN.; J yn. - the same, net cross sections;
M. - moment, bending moment;
M X.; M Y. - moments relative to the axes, respectively x-X. and y-Y.;
N. - longitudinal force;
N AD. - additional effort;
N BM. - longitudinal power from the moment in the branch of the column;
Q. - transverse force, shear force;
Q FIC - conventional transverse force for connecting elements;
Q S. - Conditional transverse force incident to the system of planks located in the same plane;
R Ba. - the estimated resistance to the stretching of the foundation bolts;
R BH - calculated resistance to the stretching of high-strength bolts;
R BP. - the calculated resistance of the crumpled of bolted compounds;
R BS. - the calculated resistance of the bolt cut;
R Bt. - the calculated resistance of the bolts of stretching;
R Bun. - Regulatory resistance of steel bolts taken equal to temporary resistance Σ B. According to state standards and technical conditions on the bolts;
R bv - the calculated resistance to the stretching of U-shaped bolts;
R CD. - calculated resistance to the diametrical compression of rinks (with free touch in constructions with limited mobility);
R Dh. - calculated resistance to high-strength wire stretching;
R LP. - the estimated resistance to the local crumpled in cylindrical hinges (pinches) with tight touch;
R P. - the calculated resistance was grounding the end surface (in the presence of fit);
R S. - the calculated resistance has become a shift;
R TH. - the estimated resistance to the stretching of steel in the direction of the thickness of the rolled;
R U. - the calculated resistance has become stretching, compression, bending by temporary resistance;
R un - Temporary resistance have become a discontinuity taken equal to the minimum value Σ B. According to state standards and technical specifications;
R WF. - the estimated resistance of the angular seams of the cut (conditional) for metal seam;
R Wu. - the calculated resistance of the butt welded joints compression, stretching, bending by temporary resistance;
R WUN. - regulatory resistance of the seam metal on temporary resistance;
R WS. - the calculated resistance of the butt welded shift connections;
R WY. - calculated resistance of butt welded joints compression, stretching and bending over the yield strength;
R wz. - the calculated resistance of the angular sutures of the cut (conditional) on the metal of the fusion boundary;
R y. - the calculated resistance has become stretching, compression, bending over the yield strength;
R yn -the yield strength of steel, taken equal to the value of the yield strength σ t according to state standards and technical conditions for steel;
S. - the static moment of the shift part of the cross section of gross relative to the neutral axis;
W X.; W y. - moments of the resistance of the cross section of gross relative to the axes, respectively x-X. and y-y;
W XN.; W yn.- moments of the resistance of the cross section of the net relative to the axes, respectively x-X. and y-Y.;
b. - width;
b EF. - calculated width;
bf. - width of the shelf (belt);
b H. - width of the protruding part of the rib, sweep;
c.; c X.; c y. - coefficients for calculating strength taking into account the development of plastic deformations during bending relative to the axes, respectively x - X, Y-Y;
e. - Eccentricity of power;
h. - height;
h EF. - the estimated height of the wall;
h W. - height of the wall;
i. - radius of inertia section;
i min - the smallest radius of the inertia of the section;
i X.; i y. - radii inertia section relative to the axes, respectively x-X.and y-Y.;
k F. - catat of angular seam;
l. - Length, span;
l C. - Stand length, columns, struts;
l D. - the length of the color;
l EF - calculated, conditional length;
l M. - Farm or column belt panel length;
l S. - Length of the plank;
l W. - the length of the weld;
l X.; l u - the calculated lengths of the element in the planes perpendicular to the axes, respectively x-X.and y-Y.;
m -relative eccentricity ( m. = eA. / W C.);
m EF. - presented relative eccentricity ( m EF. = mη.);
r. - radius;
t. - thickness;
t F. - Shelf thickness (belt);
t W. - wall thickness;
β F. and β Z. - coefficients for calculating the angular seam, respectively, on the metal of the seam and the metal of the fusion boundary;
Γ B. - coefficient of operating conditions;
Γ C. - coefficient of working conditions;
Γ N. - the reliability coefficient for its intended purpose;
γ M. - reliability coefficient by material;
Γ U. - the reliability coefficient in the calculations on temporary resistance;
η - the coefficient of influence of the section of the section;
λ - flexibility ( λ = l EF / i.);
Conditional flexibility ();
λ EF. - the reduced flexibility of the cross-section rod;
Conditional listed flexibility of the cross-sectional rod ( 
);
Conditional wall flexibility ( 
);
The greatest conditional flexibility of the wall;
λ X.; λ y. - the estimated flexibility of the element in the planes perpendicular to the axes, respectively x-X and Y-Y;
v. - the coefficient of the transverse deformation of the steel (Poisson);
Σ LOC. - local stress;
Σ X.; Σ y. - normal stresses parallel to the axes, respectively x-X.and y-y;
τ XY. - tangent stress;
φ (h., y.) - the coefficient of longitudinal bending;
φ B. - the coefficient of reducing the calculated resistance in the flexible-twisting form of loss of stability of beams;
φ E. - The coefficient of reducing the calculated resistance during an off-centrular compression.
| 1. General Provisions. 2 2. Materials for structures and connections. 3 3. Estimated characteristics of materials and compounds. 4 4 *. Accounting for working and design conditions. 6 5. Calculation of elements of steel structures on axial forces and bending. 7 Central-stretched and centrally compressed elements .. 7 Bending items .. 11 Elements subject to axial force with bend .. 15 Support parts. 19 6. Estimated lengths and limit flexibility of elements of steel structures. 19 Estimated lengths of elements of flat farms and connections. 19 Estimated lengths of elements of spatial lattice structures. 21 Estimated lengths of structural structural elements. 23 Estimated column lengths (racks) 23 limit flexibility of compressed elements. 25 Limit flexibility of stretched elements. 25 7. Check the stability of walls and waist sheets of bends and compressed elements. 26 walls of beams. 26 walls of centrally hidden and compressed and compressed-bending elements. 32 Belt sheets (shelves) of Central, Essentrennically compressed, compressed-bending and bending elements. 34 8. Calculation of leaf structures. 35 Calculation for strength. 35 Calculation for stability. 37 Basic requirements for calculating metal membrane structures. 39 9. Calculation of elements of steel structures on endurance. 39 10. Calculation of elements of steel structures for strength taking into account fragile destruction. 40 11. Calculation of steel structures. 40 Welded connections. 40 bolt connections. 42 compounds on high-strength bolts. 43 compounds with milled ends. 44 Belt connections in composite beams. 44 12. General requirements for the design of steel structures. 45 Basic provisions. 45 Welded connections. 46 Bolted compounds and compounds on high-strength bolts. 46 13. Additional requirements for the design of production buildings and structures. 48 Relative deflection and design deviations. 48 distances between temperature seams. 48 farms and structural coatings. 48 columns .. 49 communications. 49 beams. 49 crane beams. 50 leaf structures. 51 mounting mounts. 52 14. Additional requirements for the design of residential and public buildings and structures. 52 Frame buildings. 52 Hanging coatings. 52 15 *. Additional requirements for the design of supports of power lines of power, designs of open distribution devices and lines of contact networks of transport. 53 16. Additional requirements for designing the structures of the antenna structures (AC) of communication with a height of up to 500 m. . 55 17. Additional requirements for the design of river hydraulic structures. 58 18. Additional requirements for designing beams with a flexible wall. 59 19. Additional requirements for designing beams with perforated wall. 60 20 *. Additional requirements for designing structures of buildings and structures during reconstruction. 61 Appendix 1. Materials for steel structures and their calculated resistance. 64 Appendix 2. Materials for steel structures and their calculated resistance. 68 Appendix 3. Physical characteristics of materials. 71 Appendix 4 *. The coefficients of working conditions for a stretched single corner attached by one shelf bolts. 72 Appendix 5. Coefficients for calculating the strength of elements of steel structures, taking into account the development of plastic deformations. 72 Appendix 6. The coefficients for calculating the stability of the central, non-center-compressed and compressed-bending elements. 73 Appendix 7 *. Factors φ B. To calculate the beams for stability. 82 Appendix 8. Tables for calculating elements on endurance and taking into account fragile destruction. 85 Appendix 8, a. Determination of metal properties. 88 Appendix 9 *. Basic letter denotes values. 89. |
The West Siberian Metallurgical Combine was mastered by the production of shaped rolled steel (corners of equalization, chawllers, ducts) with a thickness of the shelf to 10 mm inclusively by TU 14-11-302-94 "Hire of the shaped C345 from carbon steel modified niobium, developed by the combine, JSC" Ural Institute of Metals "and agreed by CNII. Kucherenko.
The headsethnorming reports that the shaped rolling from steel C345 Categories 1 and 3 for 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 provided Rental of steel C345 Categories 1 and 3 according to GOST 27772-88.
Head of the headsethnorming V.V. Tishchenko
Introduction
The metallurgical industry was mastered by the production of hire for construction metal structures and economically doped steel C315. Strengthening, as a rule, is achieved by microallion of low-carbon calm, one of the elements: titanium, niobium, vanadium or nitrides. Alloying can be combined with rolling or heat treatment.
The achieved volume production volumes and shaped profiles from new steel C315 make it possible to fully satisfy the needs of construction at the box office with strength characteristics and cold resistance close to the standards for low-alloy steel according to GOST 27772-88.
1. Rental regulatory documentation
Currently, a series of technical specifications for hire from steel C315 has been developed.
TU 14-102-132-92 "Rolled shaped from steel C315". The Handler and Hire Manufacturer - the Nizhne-Tagil Metallurgical Combine, the sorting - channels according to GOST 8240, the equal angular profiles, non-equilibrium corner profiles, ordinary and with parallel edges of the shelves.
TU 14-1-5140-92 "Rental for building steel structures. General specifications. " Handler - Tsniychm, Rolled Manufacturer - Nizhne-Tagil Metallurgical Combine, Assortment - Lowaves according to GOST 26020, TU 14-2-427-80.
TU 14-104-133-92 "Hire of high strength for building steel structures". Handler and rental manufacturer - Orsko-Khalilovsky Metallurgical Combine, a sorting sheet with a thickness of 6 to 50 mm.
TU 14-1-5143-92 "Rent a sheet and rolled increased strength and cold resistance." Holder of the original - Tsniychm, Rolled Manufacturer - New Lipetsk Metallurgical Combine, Sortiment - Sheet Rental according to GOST 19903 thickness up to 14 mm inclusive.
TU 14-105-554-92 "Sheet Rental of high strength and cold resistance". Holder of the script and manufacturer of rolled products - Cherepovets Metallurgical plant, a range of rental according to GOST 19903 thickness up to 12 mm inclusive.
2. General provisions
2.1. Rental of steel C315 It is advisable to apply instead of rolled from low-carbon steel C255, C285 according to GOST 27772-88 for groups of structures on SNIP II-23-8I, the use of which in climatic areas of construction with the settlement temperature minus 40 ° C is not allowed. In this case, it is necessary to use the increased rolled strength from steel C315.
3. Materials for designs
3.1. Rental of steel C315 Comes four categories, depending on the tests for impact bending tests (categories are adopted the same with rolled from steel C345 according to GOST 27772-88).
3.2. Rental of steel C315 can be used in constructions, guided by the data Table. one.
Table 1
* With rolled thickness not more than 10 mm.
4. Calculation characteristics of rolled and compounds
4.1. Regulatory and calculated rolled resistance from steel C315 are accepted in accordance with Table. 2.
table 2
| Rolled thickness, mm | Regulatory resistance of rolled, MPa (kgf / mm 2) | Estimated rolling resistance, MPa (kgf / mm 2) | ||||||
| shaped | Sheet, broadband universal | shaped | ||||||
| R yn. | R un | R yn. | R un | R y. | R U. | R y. | 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 calculated resistance of welded joints of steel C315 steel for various types of compounds and stress compounds should be determined by SNIP II-23-81 * (p. 3.4, Table 3).
4.3. Estimated resistance to crumpled elements connected by bolts should be determined by SNIP II-23-81 * (p. 3.5, Table 5 *).
5. Calculation of compounds
5.1. The calculation of welded and bolted joints of steel C315 is performed in accordance with the requirements of SNiP II-23-81.
6. Production 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 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, given the calculated resistance of rolled steel C315 for different thicknesses .
On the application in the construction of a thickness of the high strength of the total strength on TU 14-104-133-92
Minstroy Russia sent ministries and departments of the Russian Federation, the republics of the republics in the Russian Federation, project and research institutes No. 13-227 of November 11, 1992 of the following content.
The Orsko-Khalilovsky Metallurgical Combine was mastered by the production of thick-walled rolled steel with a thickness of 6-50 mm for the technical conditions of TU 14-104-133-92 "Hire of increased strength for building steel structures", developed by the plant, ITMT Tsnichelete and CNII. Kucherenko.
Combine due to micro-linking of low-carbon calm steel titanium or vanadium (or other) with possible use of heat treatment and controlled rolling modes A new highly efficient type of metal from Steel C315 and C345E was obtained, whose properties are not inferior to the rental rates from low-alloy steel according to GOST 27772-88 . Method of microlation, the type of heat treatment and rolling modes chooses the manufacturer. The rental comes four categories, depending on the requirements for impact bending test, adopted in GOST 27772-88 and SNIP II-23-81 *, as well as in the FRG DIN 17100 standard (on samples with a sharp cut). The category and type of impact testing is indicated by the consumer in the order for metal rolling.
MinStroy Russia reports that the rental of steel C345E according to TU 14-104-133-92 can be applied along and instead of rolled from steel C345 according to GOST 27772-88 in designs planned by SNIP II-23-81 * "Steel structures", without recalculation of the sections of the elements and their compounds. Scope, regulatory and calculated rolling resistances from steel C315 for TU 14-104-133-92, as well as used materials for welding, calculated resistances of welded joints and crumpled elements connected by bolts should be taken on the recommendations of the CNII. Kucherenko, published below.
The Nizhnyagil Metallurgical Combine was mastered by the production of the shaped rolled steel - channels according to GOST 8240, the corners according to GOST 8509 and GOST 8510, in accordance with GOST 8239, GOST 19425, TU 14-2-427-80, broad-bars in accordance with GOST 26020 for the technical conditions of TU 14-1 -5140-82 "Hire of shaped high strength for building steel structures", developed by the plant, TsNNIFERMEM them. Bardina and Tsnieisk them. Kucherenko.
The combine due to the rational selection of the chemical composition of small-carbon steel, microlation and saturation with its nitrides and carbonitrides with grain grinding during the rolling process, a highly efficient type of rolled steel from Steel C315, C345 and C375 was obtained, the properties of which are not inferior to the rental rates from low-alloyed steels according to GOST 27772.
The rental comes four categories, depending on the requirements for the impact bending test, adopted in GOST 27772-88 and SNiP II-23-81 *, as well as in the standard of the FRG DIN 17100 (on samples with a sharp cut). The category and type of impact testing is indicated by the consumer in the order for metal rolling.
Gosstroy Russia reports that the rental of steel C345 and C375 according to TU 14-1-5140-92 can be applied along and instead of the rolled steel from steel C345 and C375 according to GOST 27772-88 in structures planned by SNIP II-23-81 * "Steel Designs ", without recalculation of the sections of the elements and their connections. Scope, regulatory and calculated rolling resistances from steel C315 for TU 14-1-3140-92, as well as used materials for welding, calculated resistances of welded joints, crumpled elements connected by bolts should be taken according to the "Recommendations" of CNII. Kucherenko, who were published in the magazine "Bulletin of Construction Equipment" No. 1 for 1993
Deputy Chairman V.A. Alekseev
Span. Poddubny V.P.
General provisions
1.1. These standards should be observed in the design of steel building structures of buildings and structures of various purposes.
Norms do not apply to the design of steel structures of bridges, transport tunnels and pipes under mighty.
When designing steel structures under special operating conditions (for example, designs of domain furnaces, main and technological pipelines, special purpose tanks, construction constructions that are subjected to seismic, intensive temperature effects or impacts of aggressive media, constructions of marine hydraulic structures), constructions of unique buildings and Constructions, as well as special types of structures (for example, pre-tense, spatial, hanging), additional requirements should be observed, reflecting the peculiarities of the work of these structures provided for by the relevant regulatory documents approved or agreed by the USSR State Building.
1.2. When designing steel structures, it is necessary to observe the standards for the protection of building structures from corrosion and fireproof standards for designing buildings and structures. An increase in the thickness of the rolled and walls of pipes to protect the structures from corrosion and increase the limit of fire resistance of the structures is not allowed.
All designs must be available for observation, cleaning, color, and also should not delay moisture and impede ventilating. Closed profiles must be sealed.
1.3 *. When designing pregnant structures:
choose the optimal in the feasibility scheme of structures and cross section of elements;
apply economical rental profiles and efficient steel;
apply for buildings and structures, as a rule, unified typical or standard structures;
apply progressive structures (spatial systems from standard elements; constructions that combine carrier and enclosing functions; precompanied, guy, thin-leaf and combined structures from different steels);
provide for the manufacturability of manufacturing and installation of structures;
apply structures that ensure the smallest labor intensity of their manufacture, transportation and installation;
provide, as a rule, the production of structures and their conveyor or large-boring installation;
provide the use of factory compounds of progressive types (automatic and semi-automatic welding, flange compounds, with millillated ends, on bolts, including high-strength, etc.);
envisage, as a rule, mounting compounds on bolts, including high-strength; Welded mounting connections are allowed with the appropriate substantiation;
perform the requirements of state standards on the design of the corresponding species.
1.4. When designing buildings and structures, it is necessary to take constructive schemes that ensure strength, stability and spatial immutability of buildings and structures in general, as well as their individual elements during transportation, installation and operation.
1.5 *. Steel and materials of compounds, restrictions on the use of Steel C345T and C375T, as well as additional requirements for the steel supplied, provided for by state standards and CEA standards or technical conditions should be indicated in the working (KM) and detailed (KMD) steel structures and in the documentation for Order materials.
Depending on the features of the structures and their nodes, it is necessary when ordering began to indicate the smaller class according to GOST 27772-88.
1.6 *. Steel structures and their calculation should satisfy the requirements of GOST 27751-88 "Reliability of building structures and grounds. The main provisions for the calculation "and ST SEV 3972-83" The reliability of building structures and grounds. Steel designs. Basic provisions for the calculation. "
1.7. The calculated schemes and the main prerequisites should reflect the actual working conditions for steel structures.
Steel structures should, as a rule, calculate both single spatial systems.
When dividing single spatial systems into separate flat designs, the interaction of elements between themselves should be taken into account with the base.
The choice of calculation schemes, as well as methods for calculating steel structures, must be made with regard to the effective use of computers.
1.8. The calculation of steel structures should, as a rule, be carried out with regard to the inelastic deformations of steel.
For statically indefinable structures, the method of calculating which, taking into account the inelastic deformations, the steel is not developed, the calculated efforts (bending and torque, longitudinal and transverse forces) should be determined under the assumption of elastic deformations of steel on an undeformed scheme.
With the appropriate technical and economic justification, the calculation is allowed to produce according to a deformed scheme, which takes into account the effect of movements of structures under load.
1.9. Elements of steel structures should have minimal sections that meet the requirements of these standards, taking into account the sorting for hire and pipes. In composite sections established by the calculation, the inepalion should not exceed 5%.
4.5. The calculated length of the elements should be determined by multiplying their free length to the coefficient
according to PP.4.21 and 6.25.
4.6. Composite elements on pliable compounds, opened by all cross section, should be calculated on strength and stability according to formulas (5) and (6), while determining both the total area of \u200b\u200ball branches. The flexibility of composite elements should be determined taking into account the compounds of the compounds by the formula
(11)
|
the flexibility of the entire element relative to the axis (Fig. 2), calculated at the calculated length without taking into account the fattyness; |
|||
|
the flexibility of the individual branch relative to the I - I axis (see cris.2), calculated according to the calculated length of the branch; With less than seven thicknesses (), the branches take \u003d 0; |
|||
|
the coefficient of bringing the flexibility determined by the formula |
|||
(12)
|
the width and height of the cross section of the element, see; |
|||
|
the calculated amount of seams in the element determined by the number of seams, according to which the mutual shift of the elements is cashed (in Fig. 2, A - 4 of the seam, in Fig. 2, b - 5 seams); |
|||
|
the estimated length of the element, m; |
|||
|
the calculated number of sections of bonds in one seam per 1 m of the element (with several seams with a different number of sections, the number of sections should be taken between all seams); |
|||
|
the coefficient of adequacy of the compounds to be determined by the formulas of Table 12. |
|||
When determining the diameter of nails, no more than 0.1 thickness of the connected elements should be taken. If the size of the pinched ends of the nails is less than 4, then the sections in the seams adjacent to them do not take into account. The value of compounds on steel cylindrical impudations should be determined by the thickness of a thinner of the connected elements.
Fig. 2. Composite elements
a - with gaskets; B - without gaskets
Table 12.
|
Type of connections |
The coefficient is |
|
|
central compression |
compression with bend |
|
|
2. Steel cylindrical braided: |
||
|
a) the thickness diameter of the connected elements |
||
|
b) diameter\u003e thickness of connected elements |
||
|
3. Oak cylindrical brazening |
||
|
4. Oak lamellar brazen |
||
|
Note: The diameters of nails and copilyons, the thickness of the elements, the width and thickness of the plate coppiers should be taken in cm. |
||
When determining the diameter of oak cylindrical copiers, no more than 0.25 thickness of the thinner of the connected elements should be taken.
Communication in the seams should be uniformly on the length of the element. In hinged-opened straight elements, it is allowed in the average quarters of the length of the length of communication in half quantities, in charge of the formula (12), the amount accepted for the extreme quarters of the length of the element.
The flexibility of the component element calculated by formula (11) should be taken no more than the flexibility of the individual branches determined by the formula
(13)
|
the sum of the moments of the inertia of the gross cross sections of individual branches with respect to their own axes parallel to the axis (see crus.2); |
|||
|
cross section of the gross element; |
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|
the calculated length of the element. |
|||
The flexibility of the composite element relative to the axis passing through the severity centers of the sections of all branches (axis in Fig.2), should be defined as for a one-piece element, i.e. Without taking into account the advantage of links, if the branches are loaded uniformly. In the case of uneven loaded branches, paragraph 4.7 should be guided.
If the branches of the component element have a different section, then the estimated flexibility of the branch in formula (11) should be taken equal to:
(14)
the definition is shown in Fig. 2.
4.7. Composite elements on fuel connections, part of the branches of which are not operated at the ends, is allowed to calculate for strength and stability by 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 opened branches;
b) the flexibility of the element relative to the axis (see cris.2) is determined by the formula (11); At the same time, the moment of inertia is adopted taking into account all the branches, and the area is only opened;
c) when determining flexibility relative to the axis (see cris.2), the moment of inertia should be determined by the formula
|
moments of inertia of cross-sections, respectively, the support and underdeveloped branches. |
4.8. The calculation on the stability of the central-compressed elements of the variable in the height of the section should be performed by the formula
|
cross cross section area with maximum dimensions; |
||
|
the coefficient that takes into account the altitude of the height of the section, determined by Table 1, Appendix 4 (for the elements of a constant section); |
||
|
the coefficient of longitudinal bending, determined by claim 4.3 for flexibility corresponding to the cross section with the maximum dimensions. |
||
Bend elements
4.9. Calculation of bending elements provided on the loss of stability of a flat deformation form (see PP.4.14 and 4.15), for strength on normal voltages should be made by the formula
|
estimated bending moment; |
||
|
calculated resistance of bending; |
||
|
the estimated moment of the resistance of the cross section of the element. For one-piece elements for the bent component elements on the supple compounds, the estimated time of resistance should be made to an equal torque of the net resistance multiplied by the coefficient; Values \u200b\u200bfor elements made up of the same layers are shown in Table. 13. When determining the weakening of the sections, located on the element section of up to 200 mm long, are taken by combined in one section. |
||
Table 13.
|
Designation of coefficients |
The number of layers in the element |
The value of the coefficients for calculating the bent component elements in flights, m |
|||
|
Note. For intermediate values \u200b\u200bof the value of the span and the number of layers, the coefficients are determined by interpolation. |
|||||
4.10. Calculation of bending elements on the durability of rocking should be carried out by the formula
|
estimated transverse force; |
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|
the static moment of gross shifted part of the cross section of the element relative to the neutral axis; |
||
|
the moment of inertia of the gross cross section of the element relative to the neutral axis; |
||
|
the calculated width of the section of the element; |
||
|
calculated resistance to the crevice during bending. |
||
4.11. The number of sections that are evenly arranged in each seam of the composite element on a plot with unambiguous line of transverse forces must satisfy the condition
(19)
|
calculated carrier communication ability in this seam; |
||
|
bending moments in the initial and finite sections of the section under consideration. |
||
Note. In the presence in the seam of links of different bearing ability, but
the same by nature of the work (for example, brazing and nails) carriers
the abilities should be summed.
4.12. Calculation of elements of one piece for strength in oblique bending should be made by the formula
(20)
|
components of the calculated bending moment for the main axes of section and |
|
|
the moments of the resistance of the cross section of the net relative to the main axes of the cross section and |
4.13. The glued curvilinear elements bended by a moment that reduces their curvature should be checked for radial tensile stresses by the formula
(21)
|
normal voltage in the extreme fiber stretched zone; |
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|
normal voltage in the intermediate fiber section for which radial tensile stresses are determined; |
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|
the distance between the extreme and the fibers under consideration; |
||
|
the radius of the curvature of the line passing through the center of gravity of the plot of normal stretching stresses concluded between the extreme and considered fibers; |
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|
the calculated wood resistance to stretching across the fibers received according to claim 7 Table 3. |
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4.14. Calculation of the stability of a flat form of deformation of the bending elements of the rectangular section should be made by the formula
|
maximum bending moment on the site under consideration |
||
|
the maximum moment of brutate resistance on the site under consideration |
||
The coefficient for the bent elements of the rectangular cross section, hingedly fixed from the offset from the bending plane and fixed from rotation around the longitudinal axis in the reference sections, should be determined by the formula
|
the distance between the supporting sections of the element, and when fixing the compressed edge of the element at intermediate points from the displacement from the bend plane - the distance between these points; |
||
|
cross-section width; |
||
|
maximum cross section height on the site; |
||
|
the coefficient depending on the form of the bends of bending moments on the site defined by Table 2, 3 of Appendix 4 of these standards. |
||
When calculating bent moments with a linearly changing in length of height and a constant cross-sectional width, which does not have fastenings from the plane for a stretched edge, or with the coefficient by formula (23), multiplied to an additional factor, the values \u200b\u200bare shown in Table 2. At \u003d 1.
When reinforcing the bending plane at intermediate points of the stretched edge of the element on the area of \u200b\u200bthe coefficient defined by formula (23), the coefficient should be multiplied by the coefficient:
:= 
(24)
|
central angle in radians, determining the section of the circular outlines (for rectilinear elements); |
||
|
the number of intermediates reinforced (with the same step) points of the stretched edge on the site (with an amount of equal to 1). |
||
4.15. Checking the stability of a flat form of deformation of bending elements of foreign or box cross sections should be performed in cases where
|
the width of the concise belt of the cross section. |
Calculation should be made by the formula
|
the coefficient of longitudinal bending from the bending plane of a compressed belt of an element, determined by claim 4.3; |
||
|
estimated compression resistance; |
||
|
the moment of resistance of the gross cross section; In the case of plywood walls - the present time of resistance in the bending plane of the element. |
||
Elements subject to axial force with bend
4.16. The calculation of non-center-stretched and stretched bending elements should be made by the formula
(27)
4.17. Calculation of the strength of the extracently compressed and compressed-bending elements should be made by the formula
(28)
Notes: 1. For hinged-opened elements with symmetric eporas
bending moments of sinusoidal, parabolic, polygonal
and close to them outlines, as well as for console elements it follows
determine the formula
|
the coefficient varying from 1 to 0, which takes into account the additional moment from the longitudinal force due to the deflection of the element determined by the formula |
||||
|
bending moment in the estimated section without taking into account the additional moment of longitudinal force; |
||||
|
the coefficient determined by formula (8) p.4.3. |
||||
2. In cases where, in the hinged-operated elements of the fusion of bending moments, have a triangular or rectangular outline, the coefficient of formula (30) should be multiplied by the correction factor:
(31)
3. With the asymmetrical loading of the hinged-opened elements, the bending moment value should be determined by the formula
(32)
|
bending moments in the estimated section of the element from the symmetric and cosimmetric components of the load; |
||
|
the coefficients determined by formula (30) with the magnitudes of the flexibility corresponding to the symmetric and co-symmetric forms of longitudinal bending. |
||
4. For the elements of the variable in the height of section, the area in the formula (30) should be taken to maximize in the height of the section, and the coefficient should be multiplied by the coefficient received by Table 1.
5. With the ratio of the bend to stresses from compression less than 0.1, the combat-bending elements should also be checked for stability by formula (6) without taking into account the bending moment.
4.18. Calculation of the stability of a flat form of deformation of compressed-bending elements should be made by 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; |
||
|
the coefficient of longitudinal bending, determined by formula (8) for the flexibility of the element of the element of the estimated length from the deformation plane; |
||
|
the coefficient determined by the formula (23). |
||
In the presence in the element on the plot of fixtures from the deformation plane from the side stretched from the edge of the edge, the coefficient should be multiplied by the coefficient of formula (24), and the coefficient - the coefficient by the formula
(34)
When calculating the elements of the variable in the height of section, not having fasteners from the plane for a stretched edge or with coefficients and determined by formulas (8) and (23), it should be further multiplied by the coefficients and shown in Table 1 and 2 .four. For
4.19. In composite compressed-bending elements, the stability of the most intense branch should be checked if the calculated length of it exceeds seven thickness of the branch, according to the formula
(35)
The stability of the compressed-bending component element from the bend plane should be checked by formula (6) without taking into account the bending moment.
4.20. The number of sections of links that are evenly placed in each seam of the compressed-bending component in a plot with unambiguous laying of transverse forces when the compressive force is applied throughout the cross section must satisfy the condition
|
the static moment of gross shifted part of the cross section relative to the neutral axis; with hinged-fixed ends, as well as with a hinge fixation in the intermediate points of the element - 1; with one articulated and fixed and other pinched late - 0.8; with one pinched and other free loaded end - 2.2; in both attacked ends - 0.65. In the case of distributed evenly along the length of the element of the longitudinal load, the coefficient should be taken equal to: in both hinge and fixed ends - 0.73; with one pinched and other free end - 1.2. The calculated length of intersecting elements interconnected at the intersection site should be taken equal to: when checking stability in the plane of structures - the distance from the center of the node to the intersection point of the elements; when checking the stability from the design plane: a) in the case of intersection of two compressed elements - the total length of the element; |
Name of structural elements |
Limit flexibility |
||
|
1. Compressed belt, references and reference racks Farms, columns |
||||
|
2. Other squeezed elements of farms and other cross-cutting structures |
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|
3. Compressed link elements |
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|
4. Stretched farm belts in the vertical plane |
||||
|
5. Other stretched elements of farms and other cross-cutting structures |
||||
|
For support air lines | where the coefficient is accepted in Table 1.
The amount should be taken at least 0.5;
c) In the case of intersection of a compressed element with a stretched equal in the magnitude of the force - the largest length of the compressed element measured from the center of the node to the intersection point of the elements.
If intersecting elements have a composite section, then in formula (37), appropriate flexibility values \u200b\u200bdetermined by formula (11) should be substituted.
4.22. The flexibility of the elements and their individual branches in wooden structures should not exceed the values \u200b\u200bindicated in Table. 14.
Features of calculation of glued elements
from plywood with wood
4.23. The calculation of glued elements from plywood with wood should be performed according to the method of the transverse cross section.
4.24. The strength of stretched plywood plates (Fig. 3) and panels should be checked by the formula
the moment of resistance of the cross section shown in plywood, which should be determined in accordance with the indications of clause 4.25.
4.25. The present time of the resistance of the transverse section of glued slabs from plywood with wood should be determined by the formula
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distance from the center of gravity of the centered section to the outer face of the trim; |
Fig.3. Cross section of glued plates from plywood and wood
the static moment of the shift part of the given section relative to the neutral axis;
estimated resistance to the rocking of wood along the fibers or plywood along the fibers of the outer layers;
the calculated width of the section, which should be taken equal to the total width of the ribs of the frame.