RU2639209C1 - Method of determining fire safety characteristics of elements and materials of complex facing of steel beam with corrugated wall - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: method for determining the fire safety characteristics of elements and materials of the complex facing of a steel beam with a corrugated wall includes determining the type of rolled steel, the steel grade and the geometrical characteristics of the welded I-beam of the steel beam; identification of the number of sides of the cross-section of the steel beam exposed to heat under fire conditions; finding the reduced metal thickness of the welded I-beam elements and the intensity of force stresses in the metal; establishing the indices of thermal diffusion of the insulation coating of facing materials; determining the required fire protection degree of the welded I-beam elements; finding the required fire resistance of the steel beams of the building. First, the element of the welded I-beam, weakest in the static and thermal sense, is revealed: the corrugated wall, the lower and the upper flanges; a reference point in the section of the welded I-beam element is found, the type of the reference material and the materials corresponding to it that make up the complex facing are determined; the index of the heating conditions of the reference point is determined, the dimensions of the bent profile for the welded I-beam shelves in the form of a channel and the angle for the steel beam are chosen, then the reduced thickness of the metal of the welded I-beam element is calculated with the gain. Determining the required fire protection degree for the elements of the welded I-beam of the steel beam with the corrugated wall, the optimal geometric and fire safety characteristics of the elements and materials for the complex fire protection of the welded I-beam of the steel beam are found.

EFFECT: invention allows to increase the accuracy of the choice of the geometric dimensions of the elements of the welded I-beam of the steel beam with a corrugated wall and the materials of its complex facing, optimal for fire resistance and sufficient for fire safety, to reduce the consumption of steel and large-sized sheet and plate materials of the facing, to increase the resource-saving in the process of carrying out the fire protection facing of a welded I-beam of a steel beam with a corrugated wall.

7 cl, 5 dwg, 1 tbl

Description

The invention relates to the field of fire safety of buildings and structures (hereinafter referred to as buildings) and relates to a method for determining the structural fire protection of a steel supporting rod of a beam with a corrugated wall made in the form of a composite welded I-beam using large-sized sheet, plate and roll cladding (coating).

Unprotected steel beams with a corrugated wall when exposed to fire in a building fire quickly (after 5 ÷ 20 min) lose their bearing capacity, collapse themselves and contribute to the collapse of other building structures, which leads to significant material losses.

The closest technical solution to the invention by the totality of features is a method for determining the fire-technical characteristics of the elements and materials of a complex cladding of a steel beam of a building, including determining the type of rolled steel and the geometric characteristics of the steel supporting rod of the steel beam, the type of steel profile for the complex cladding frame; finding the intensity of power stresses in the metal; identification of the types of materials constituting a complex cladding, the establishment of indicators of thermal diffusion of cladding materials; determination of the degree of fire protection of a steel supporting rod of a steel beam with complex lining; finding the required fire resistance limit of a steel beam of a building / Patent No. 2522110 (2006.1), IPC Е04В 1/94. Fire protection method for an I-beam of a building / N.A. Ilyin, A.P. Shepelev, P.N. Slavkin, P.P. Ibatullin. Application SSASU 10.25.2012; publ. 04/27/2014 Bull No. 12 / [1] - taken as a prototype /.

For reasons that impede the achievement of the following technical result when using the known method for determining the fire-technical characteristics of the complex cladding of a steel beam of a building adopted as a prototype, the known method has a large error in determining the geometric dimensions of the steel elements of the complex cladding frame, as well as geometric and thermophysical characteristics of sheet and plate cladding.

The essence of the invention is to reduce the consumption of steel and large-sized sheet and plate materials of the cladding, increasing resource conservation in the process of fire retardant cladding of a welded I-beam of a steel beam with a corrugated wall.

The technical result is an increase in the accuracy of choosing the optimal fire resistance and geometric dimensions sufficient for fire safety of the elements of a welded I-beam of a steel beam with a corrugated wall and materials of its complex cladding.

The specified technical result when using the invention is achieved by the fact that in the known method for determining the fire-technical characteristics of the elements and materials of the complex cladding of a steel beam with a corrugated wall, which includes determining the type of rolled steel, steel grade and geometric characteristics of the welded I-beam of the steel beam, identifying the number of sides of the cross section steel beams exposed to heat in a fire; finding the reduced thickness of the metal of the elements of the welded I-beam of a steel beam and the intensity of power stresses in the metal; setting indicators of thermal diffusion of the insulation coating of cladding materials; determination of the required degree of fire protection of the elements of a welded I-beam of a steel beam; finding the required fire resistance limit of the steel beam of the building, the peculiarity is that first they reveal the weakest element in the static and thermal respects of the welded I-beam: the corrugated wall, lower and upper shelves, find the control point in the cross section of the welded I-element, reveal the type of the reference material and the corresponding materials that make up the complex cladding; identify the indicator of the heating conditions of the control point, select the dimensions of the bent profile for the shelves of the welded I-beam in the form of a channel and a corner of a steel beam, then calculate the reduced metal thickness - T _sr , mm - of the element of the welded I-beam with reinforcement, using equation (1)

where A _s is the area of the metal section of the element of the welded tee, mm ² ; P ₀ - perimeter of the heating element of the welded tee, mm;

resistance time - r _us , min - of an element of a welded I-beam without fire protection to the thermo-force action is calculated by the analytical expression (2)

where T _sr is the reduced thickness of the metal element of the welded I-beams, cm; J _σs is the intensity of power stresses in the element of the welded I-beams (0.1 ÷ 1.0);

the required degree of fire protection of an element of a welded double tee - C, cm - with a complex lining is calculated by the logarithmic equation (3)

where R _in - the required limit of fire resistance of the steel beam of the building, min, r _us - time of resistance to the thermal force of the element of the welded I-beam without taking into account its fire protection, min;

the required thickness of the cladding material - δ _Tr , mm - element of the welded I-beams is determined by the exponential equation (4)

where C is the required degree of fire protection of the welded double tee element; D _W - indicator of thermal diffusion of the material of the fire retardant lining, mm ² / min; m ₀ - indicator of the heating conditions of the control point of the element of the welded I-beams (0.5 ÷ 1.0);

reduced thickness - b _r , mm - of the complex lining of the welded I-beam element is calculated using equation (5)

where δ _et and δ _{r, mp} is the thickness of the layer of the reference material and the required thickness of the reduced complex cladding, mm; D _et and D _W - indicator of thermal diffusion of the reference and compared to the material of the lining, mm ² / min;

the thickness of the lining material of the element of the welded I-beams, compared with the reference material - δ _PL , mm - is calculated by the algebraic equation (6)

where δ _{r, mp} and δ _et - the thickness of the required reduced layer and the reference coating layer, mm; D _W and D _et - an indicator of thermal diffusion of the compared layer and the reference layer of the complex cladding, mm ² / min;

the structural thickness of the complex lining of the welded I-beam element - b _kp , mm - is determined by the expression (7)

where δ _et and δ _PL - layer thickness of the reference material of the cladding and the material compared with it, mm

The element of the welded I-beams, which is the least weak in the static and thermal respects, is the element of the welded I-beams: corrugated wall, lower and upper shelves, having the shortest resistance to thermo-force impact without taking into account its fire protection - r _{us, min} , min.

The control point in the cross section of the flange of a welded I-beam is defined as a directionally displaced point of placement of the average temperature of an element of a welded I-beam unevenly heated over the cross section.

When the flange of the welded tee is parallel to the x axis, the abscissa ( a _x ) and the ordinate ( a _y ) are determined respectively by equations (8) and (9)

where δ _x and δ _y are the thickness of the complex lining of the insulating coating of the flange of the welded I-beams, respectively, along the x and y axis, mm; and _x and a _y - the depth of the control point of the cross section of the flange of a welded I-beam along the x and y axis, mm; b is the width of the flange of the welded I-beam, mm; In - the width of the cross section of a lined steel beam with a corrugated wall, mm

A control point in the cross section of the corrugated wall of a welded I-beam with symmetrical double-sided heating is assigned in the middle of its cross section: ( a _x = d / 2, mm, here a _x is the depth of the control point along the x axis; d is the thickness of the corrugated wall, mm) .

The indicator of the heating conditions (m ₀ ) of the welded I-element with a three-way supply of heat to the control point of the cross-section of the welded I-element is determined by the analytical equation (10)

where a _y ; and _y1 and a _y2 are the ordinates of the control point of the cross section of the element of the welded tee, mm; δ _x is the thickness of the insulation coating along the x axis, mm

The indicator of the heating conditions (m ₀ ) of the welded I-element with two-sided asymmetric heat supply to the control point of the section of the welded I-element is determined by the power equation (11)

where a _y is the ordinate of the control point of the cross section of the welded I-beams, mm; δ _x is the thickness of the insulating coating of the welded I-beam element along the x axis, mm.

A causal relationship between the totality of features and the technical result of the invention is as follows:

using the proposed logarithmic equation to find the required degree of fire protection of the corrugated wall, lower and upper shelves of the welded I-beams allows to determine with lesser error the required thickness of the materials of the complex cladding of steel beam elements;

the use of the proposed analytical equation to find the directionally displaced (control) point of placement of the average temperature of a non-uniformly heated section of the corrugated wall, lower and upper shelves of the welded I-beam reduces the error in determining the fire-technical characteristics of the complex cladding of elements of a welded I-beam by 15 ÷ 20%;

determination of the time of resistance to the thermal force of the corrugated wall, lower and upper shelves of the welded I-beam using the proposed analytical equation allows with a lesser error to identify the least weak element of the steel beam in the conditions of a standard fire test;

the use of thermal diffusion indicators of the reference material and the material of the integrated cladding of welded I-beams for comparison with it allows us to more accurately and expressively determine the structural thickness of the cladding materials of the corrugated wall, lower and upper shelves of the steel beam;

express calculation of the value of the indicator of the heating conditions of the control point of the corrugated wall, lower and upper shelves of the welded I-beams is performed according to the proposed analytical equations for the case of two - and three-sided heat supply to the control point;

20–30% reduction in the consumption of materials for complex cladding due to a more accurate determination, which fully corresponds to the required thickness;

a decrease in the required amount of computer main memory when using the proposed algorithm for calculating the fire-technical characteristics of a complex steel beam cladding by 15–20 times, compared with the existing method of heat engineering calculation using nomograms for heating the cladding materials.

In FIG. 1, 2, 3 shows a diagram of a steel beam with a corrugated wall: section AA - longitudinal section (Fig. 1); section BB - cross section (Fig. 2); section B-B is a plan of a beam with a corrugated wall (Fig. 3), where the following designations are adopted: 1 - lower shelf, 2 - upper shelf; 3 - corrugated wall; h and b are the height and width of the welded I-beams; d is the thickness of the corrugated wall, mm; δ is the thickness of the flange of the welded tee, mm.

In FIG. 4 shows a welded I-beam, the shelves of which are equipped with bent steel channels - elements of the frame of the protective belt (heating the cross section of the beam from three sides): 1 - lower shelf; 2 - upper shelf; 3 - corrugated wall; 4 - channel of the lower shelf; 5 - channel of the upper shelf; 6 - weld; h ₁ × b ₁ × s ₁ - the height, width and thickness of the bent channel attached to the stretched shelf of the welded I-beam of a steel beam; h ₂ × b ₂ × s ₂ - the height, width and thickness of the bent channel attached to the compressed flange of a welded I-beam of a steel beam.

In FIG. 5 shows a fireproof welded I-beam of a steel beam (the shelves of which are equipped with bent steel channels: 4 - the channel of the lower shelf; 5 - the channel of the upper shelf; 7 - gypsum plasterboards; 8 - the mineral wool plate of the welded I-beam shelf; 9 - the mineral wool corrugated wall plate (heating - double-sided ); 10 - control points of the lower flange of the welded I-beam (three-sided heating); t _st ° C - direction of heat supply in the conditions of a standard test; g ₀ - linear test load on the supporting corrugated beam, kN; H × B - total height and width of steel beams with fire-retardant lining, mm; a _x and a _y are the depth of laying the control point of the cross section of the welded I-beam of the steel beam along the x and y axes, mm; δ _x is the thickness of the lining of the flange of the welded I-beam of the steel beam along the xy axis, mm).

Information confirming the possibility of applying the invention to obtain the specified technical result.

The building of the institution of higher education was reconstructed, where the project provides for steel beams with complex cladding. Fire and technical characteristics of the building and its supporting beams: functional fire hazard class - F 4.2; degree of fire resistance - 1 (first); class of constructive fire hazard - СО (not fire hazardous); number of floors - 6; standard limit of fire resistance of the supporting beam R _in = 120 min (table. 21, Federal Law of the Russian Federation No. 123-2012).

Example 1. Fireproof steel beam with a corrugated wall with a height of h _st = 1000 mm contains a steel supporting rod in the form of a composite welded I-beam: h × b × δ × d = 1060 × 450 × 30 × 2 mm; A _sm = 270 cm ² ; cross-sectional heating of the beam from three sides; temperature test standard test; heat supply to the control point of the cross-section of the flange of the welded double tee is two-sided; steel elements of the protective belt frame for the shelves of a welded I-beam - 2 bent channels for each shelf: h ₁ × b ₁ × s ₁ = 120 × 60 × 4 mm; A _s1 = 2 × 9 = 18 cm ² , the cross-sectional area of the shelves of the welded I-beam A _s = A _sm + A _s1 = 135 + 18 = 153 cm ² ; the intensity of power stresses in the metal of the lower shelf is equal to J _σs = J _he = 0.625; in the corrugated wall - J _σs = 0.1; the required fire resistance limit of the load-bearing beam is R _in = 120 min for a building of I (first) degree of fire resistance; integrated lining from the bottom of the lower flange of a welded I-beam of a steel beam: mineral wool plate P-100; γ = 100 kg / m ³ - thermal diffusion index D _W = 33.53 mm ² / min; two plasterboard sheets (reference material) with a thickness of δ _GCR = 2⋅12.5 = 25 mm; D _GCR = D _et = 19 mm ² / min, the coating material from the sides of the lower shelf is a mineral wool board P-100; an indicator of the heating conditions of the control point of the lower shelf m ₀ = 0.5; also, a compressed shelf - m ₀ = 1; the material of the corrugated wall lining is mineral wool plate P-100, the indicator of the conditions of two-sided heating is m _{o, g / s} = 0.5.

Determine the thickness of the layers of the complex lining of the shelves and the corrugated wall of the welded I-beam of the steel beam.

Decision

1. The reduced metal thickness of the lower flange of the welded I-beam of a steel beam with four-sided heat supply is calculated using equation (1)

T _sr = A _s / P ₀ = 153 / [2 (b + δ) -d] = 153 / [2 (45 + 3) -0,2] = 16 mm = 1.6 cm

, мин - вычисляют по аналитическому выражению (2)2. The resistance time to the thermal force of a standard test of the lower shelf of a steel beam without fire protection -

, min - calculated by the analytical expression (2)

3. The required degree of fire protection of the lower shelf with integrated cladding is calculated by the logarithmic equation (3)

4. The required thickness of the complex cladding, reduced to the reference material, is determined by the exponential equation (4)

5. The reduced thickness of the complex lining of the lower flange is calculated using equation (5)

b _r = δ _et + (δ _{r, tr} -δ _st ) ⋅D _et / D _W = 25 + (54-25) ⋅19 / 33.53 = 25 + 16.5 = 41.5 mm.

6. The required thickness of the mineral wool plate P-100 for facing the lower shelf is calculated according to equation (6)

δ _PL = (δ _{r, tr} -δ _et ) ⋅D _W / D _et = (57-25) ⋅33.53 / 19 = 56.5 mm;

δ _{pl, r} = δ _{r, tr} ⋅D _W / D _floor = 57⋅33.53 / 19 = 100.6 mm.

7. The structural thickness of the complex lining of the lower shelf is calculated from the expression (7)

8. The reduced thickness of the metal of the upper shelf with a one-sided supply of heat to the welded I-beam of a steel beam is calculated using equation (1)

, мин - вычисляют по выражению (2)9. The time of resistance to fire exposure of the upper shelf without fire protection -

, min - calculated by the expression (2)

10. The required degree of fire protection of the upper shelf is calculated by the logarithmic equation (3)

11. The required thickness of the lining of the upper shelf with a P-100 mineral wool slab (thermal diffusion index D _W = 33.53 mm ² / min, m ₀ = 1) is determined by equation (4)

12. The reduced metal thickness of the corrugated wall (with a symmetrical two-sided heat supply - m ₀ = 0.5) is calculated using equation (1)

T _{sr, g / s} = A _{s, st} / P _{0, st} = dh _st / 2⋅h _st = d / 2 = 0.212 = 0.1 cm.

13. The time of resistance to the fire effect of the corrugated wall without fire protection - r _rs , min - calculated by the expression (2)

r _{us, g / s} = 6⋅ {T _{sr, r / s} + 18.33⋅⎣ (1-J _σs ) ^1/2 -0.5⎦} = 6⋅ {0.1 + 18.33⋅ [ (1-0.1) ^1/2 -0.5} = 6⋅ (0.1 + 8.2) = 50 min.

14. The required degree of fire protection of the corrugated wall is calculated according to equation (3)

15. The required thickness of the lining of the corrugated wall with a mineral wool plate P-100, with m _{0, g / s} = 0.5; D _W = 33.53 mm ² / min, determined using equation (4)

δ _pl, ct = 07⋅C _{g / s} ⋅D _W ^0.8 / 0.5 = 0.7⋅3.33⋅33.53 ^0.8 / 0.5 = 77.5 mm.

The calculation results are summarized in the table.

The proposed method for determining the fire-technical characteristics of the complex cladding of a steel beam of a building was applied during the reconstruction of the educational building No. 2 of the SASAS (Samara, 2012/15).

Information sources

1. Patent No. 2522110 (2006.1), IPC Е04В 1/94. Fire protection method for an I-beam of a building / N.A. Ilyin, A.P. Shepelev, P.N. Slavkin, P.P. Ibatullin, application. SSASU 10.25.2012; publ. 04/27/2014 Bul. No. 12.

Claims (35)

1. The method of determining the fire-technical characteristics of the elements and materials of the complex cladding of a steel beam with a corrugated wall, including determining the type of rolled steel, steel grade and geometric characteristics of a welded I-beam of a steel beam; identification of the number of sides of the cross section of a steel beam exposed to heat in a fire; finding the reduced thickness of the metal elements of the welded I-beams and the intensity of power stresses in the metal; setting indicators of thermal diffusion of the insulation coating of cladding materials; determination of the required degree of fire protection of welded I-beam elements; finding the required fire resistance limit of the steel beam of the building, characterized in that first they reveal the weakest in static and thermal respects element of the welded I-beams: corrugated wall, lower and upper shelves, find a control point in the cross section of the element of the welded I-beams, reveal the type of the reference material and the materials corresponding to it constituting a complex cladding; identify the indicator of the heating conditions of the control point, select the dimensions of the bent profile for the shelves of the welded I-beam in the form of a channel and an angle for a steel beam, then calculate the reduced metal thickness - T _sr , mm - of the element of the welded I-beam with reinforcement, using equation (1) T _sr = A _s / P ₀ ; where A _s is the area of the metal section of the element of the welded tee, mm ² ; P ₀ - perimeter of the heating element of the welded tee, mm; resistance time - r _us , min - of an element of a welded I-beam without fire protection to the thermo-force action is calculated by the analytical expression (2)

where T _sr is the reduced thickness of the metal element of the welded I-beams, cm; J _σs is the intensity of power stresses in the element of the welded I-beams (0.1 ÷ 1.0); the required degree of fire protection of an element of a welded double tee - C, cm - with a complex lining is calculated by the logarithmic equation (3) C = ln⋅ [0.4⋅ (R _in -r _us )]; where R _in - the required fire resistance of the steel beam of the building, min, r _us is the time of resistance to the thermal force effect of the element of the welded I-beam without taking into account its fire protection, min; the required thickness of the cladding material - δ _Tr , mm - element of the welded I-beams is determined by the exponential equation (4) δ _mp = 0,7⋅C⋅D _Mo ^0,8 / m _0; where C is the required degree of fire protection of the welded double tee element; D _W - indicator of thermal diffusion of the material of the fire retardant lining, mm ² / min; m ₀ - indicator of the heating conditions of the control point of the element of the welded I-beams (0.5 ÷ 1.0); reduced thickness - b _r , mm - of the complex lining of the welded I-beam element is calculated using equation (5) b _r = δ _et + (δ _{r, tr} -δ _et ) ⋅D _et / D _W ; where δ _et and δ _{r, mp} is the thickness of the layer of the reference material and the required thickness of the reduced complex cladding, mm; D _et and D _W - indicator of thermal diffusion of the reference and compared to the material of the lining, mm ² / min; the thickness of the lining material of the element of the welded I-beams, compared with the reference material - δ _PL , mm - is calculated by the algebraic equation (6) δ _PL = (δ _{r, tr} −δ _et ) ⋅D _W / D _et ; where δ _{r, mp} and δ _et - the thickness of the required reduced layer and the reference coating layer, mm; D _W and D _et - an indicator of thermal diffusion of the compared layer and the reference layer of the complex cladding, mm ² / min; the structural thickness of the complex lining of the welded I-beam element - b _kp , mm - is determined by the expression (7) b _kn = δ _et + δ _PL ; where δ _et and δ _PL - layer thickness of the reference material of the cladding and the material compared with it, mm 2. The method according to p. 1, characterized in that the element of the welded I-beams being the least weak in the static and thermal respects is the element of the welded I-beams: corrugated wall, lower and upper flanges, having the shortest resistance to thermal force, r _{us, min} , min - excluding its fire protection. 3. The method according to p. 1, characterized in that the control point in the cross section of the flange of a welded I-beam is defined as a directionally-displaced point of placement of the average temperature of an element of a welded I-beam unevenly heated over the section. 4. The method according to p. 1, characterized in that when the location of the flange of the welded I-beams parallel to the x axis, the abscissa (a _x ) and the ordinate (a _y ) are determined respectively by equations (8) and (9)

and _y = δ _y ; where δ _x and δ _y are the thickness of the complex lining of the insulating coating of the flange of the welded I-beams, respectively, along the x and y axis, mm; and _x and a _y - the depth of the control point of the cross section of the welded I-beams along the x and y axis, mm; b is the width of the flange of the welded I-beam, mm; B is the width of the section of the lined steel beam, mm, with a corrugated wall. 5. The method according to p. 1, characterized in that the control point in the cross section of the corrugated wall of the welded I-beam with symmetrical double-sided heating is assigned in the middle of the cross section: a _x = d / 2, mm, here a _x is the depth of the control point axis x, d - corrugated wall thickness, mm. 6. The method according to p. 1, characterized in that the indicator of the heating conditions (m ₀ ) of the welded I-member with three-way heat supply to the control point of the section is determined by the analytical equation (10) m ₀ = (a _y1 / δ _x ) ^0.5 / [1.5+ (a _y1 / a _y2 ) ⁴ ]; where a_y1 and but_y2 - ordinates of the control point of the cross-section of the element of the welded tee, mm; δ_x - the thickness of the insulation coating of the welded I-beam element along the x axis, mm. 7. The method according to p. 1, characterized in that the indicator of the heating conditions (m ₀ ) with two-sided asymmetric heat supply to the control point of the cross-section of the welded I-element is determined by equation (11) m ₀ = 0.5⋅ (a _y / δ _x ) ^0.5 ; where a _y is the ordinate of the control point of the cross section of the element of the welded I-beams, mm; δ _x is the thickness of the insulating coating of the welded I-beam element along the x axis, mm.

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