RU2522110C2 - Method of building i-beam fire protection - Google Patents

Abstract

FIELD: fire safety equipment.

SUBSTANCE: invention relates to the field of fire safety of buildings and relates to the method of structural fire protection of the steel beam of the building. The steel I-beam which is attached to the steel rolled profiles of channel and a pair of corners, is equipped with mounting nuts and set screws with countersunk heads and a threaded pointed end. The elements of the facesheet are attached close to the I-beam shelves, the elements of the slabby facing are close to the wall of the I-beam. The fireproof facing element thickness is preliminary determined, taking into account the thermophysical properties of its materials and the heating conditions in a fire.

EFFECT: improving reliability of fastening the elements of large size facing, increase in the fire resistance limit of steel beam, reducing the risk of collapse of the beam in the initial stage of fire.

11 cl, 3 dwg

Description

The invention relates to the field of fire safety of buildings and structures (hereinafter referred to as buildings) and relates to a method of constructive fire protection of a steel supporting rod of a beam, made in the form of a beam I-beam, using large-sized sheet, plate and roll cladding.

Unprotected steel structures of a building when exposed to fire in a fire quickly (after 15 ÷ 20 min) lose their bearing capacity, collapse themselves and contribute to the collapse of other building structures, which leads to significant material losses.

A known method of fire protection of an I-beam of a building, the lining of which is represented in the form of two shells made of hollow ceramic stone, closely laid to the wall and the lower shelf of the I-beam / Roitman M.Ya. Fire prevention in the construction industry / VIPPSH, RIO. - M., 1975, - 525 s .; (Ch.5 Fire protection of metal structures; §5.2. Improving the fire resistance of steel structures; Fig.5.2, p.116-117) /.

The reasons that impede the achievement of the technical result indicated below when using the known method of I-beam fire protection include the fact that in the known method the cladding elements are made of heavy material - ceramic stone with a density of 1200 ÷ 1400 kg / m ³ , this significantly increases the mass of fire-retardant cladding, the presence of internal voids (25 ÷ 30%) in ceramic stone favors the rapid heating of the cladding to critical heating temperatures of the steel beam and the lowering of the fire resistance by 20 ÷ 25%; the building industry does not produce a cladding in the form of ceramic stone shells; therefore, it is neither industrial nor economical.

There is a method of fire protection of an I-beam of a building, in which a fireproof lining of large sheets and plates is installed on a bearing in the form of a gap of at least 25 mm between the fireproof lining and the faces of the protected steel supporting rod; the fireproof cladding frame is made in the form of a frame consisting of steel longitudinal and transverse elements with a height of 40 ÷ 75 mm; the steel elements of the frame are fastened to each other by self-tapping screws 5 × 25 ÷ 5 × 45 / Romanenkov I.G., Levitas F.A. Fire protection of building structures. - M .: Stroyizdat, 1991 .-- 320 p .; (Chap. 4 Structural fire protection methods; Sec. 4.2 Large-sized sheet, plate and roll cladding; Fig. 8, p.131-133) /.

The reasons that impede the achievement of the technical result indicated below when using the known method of fire protection of an I-beam of a building include the fact that a significant number of carcass elements are used in the known method and, as a result, the metal consumption for the manufacture of a carcass for fireproof cladding is increased; when designing voids and gaps between the wall and the flanges of the I-beam and the plates of the protective lining, they take increased dimensions of the cross section of the lined beam (the cross-sectional area increases by 40 ÷ 45%; the consumption of lining materials - by 30 ÷ 35%); the design limit of fire resistance of the fireproof column is reduced by 25 ÷ 30%; reliability of fastening of elements of large-sized sheet and plate cladding is reduced; the corrosion resistance of the steel supporting rod and the maintainability of the fire retardant lining are reduced (if it is possible to obtain end-to-end spalls).

The closest technical solution to the invention in terms of features is a method of fire protection of an I-beam of a building, in which a steel supporting rod with anchors on its side faces is used, a frame made of C-shaped profiles, consisting of longitudinal elements with bends along the edges of the shelves and transverse elements, lining of sheet materials, which is attached at a ratio of 40 ÷ 50 mm with the formation of gaps between the shelves of the I-beam (the area of empty space between the shelves and the wall of the I-beam No. 20 and the elements of the faces Application flame retardancy in the cross section of the column of the total area is 80 ÷ 85%) /a.s. SU 887755, MKI-3 E04B 1/94, Building unit of the building / Yu.V. Pokrovsky, V.V. Fedorov, M.M.Karbachinsky and others; declared 02.21.80; publ. 12/12/81; Bull. No. 45 /, and which is taken as a prototype.

For reasons that impede the achievement of the following technical result when using the known method of fire protection of an I-beam of a building adopted as a prototype, the known method uses a significant number of carcass elements and, as a result, increases the metal consumption for the manufacture of a carcass for fireproof cladding; when designing voids and gaps between the wall and the flanges of the I-beam and the plates of the protective cladding, the dimensions of the cross section of the lined beam are increased (the cross-sectional area increases by 75 ÷ 90%; the consumption of facing materials - by 65 ÷ 70%); the design limit of fire resistance of the fireproof beam is reduced by 30 ÷ 35%; reliability of fastening of elements of large-sized sheet and plate cladding is reduced; the corrosion resistance of the steel supporting rod and the maintainability of the fire retardant lining are reduced (if it is possible to obtain mechanical damage and through spalls); it is not justified to determine the design thickness of the elements of the sheet of fire-retardant cladding of the steel supporting rod of the beam, depending on the degree of fire resistance of the building, the heating conditions of the I-beam and the thermal diffusion index of the cladding materials.

The invention consists in the following. The problem to which the claimed invention is directed, is to increase the fire resistance and operational reliability of the fireproof I-beam of the building, as well as to improve the fire-technical and economic indicators of steel structures of buildings.

EFFECT: increased reliability of fastening of elements of a large-sized sheet and plate fireproof lining of an I-beam and frame elements for it; reduction in the number of frame elements for fire retardant cladding; weight reduction of metal and facing materials; a decrease in the cross-sectional area of the fire-protected I-beam by 30 ÷ 55%; increasing the fire resistance of a steel beam with a supporting rod in the form of a beam I-beam by 25 ÷ 30%; increased safety during fire fighting and rescue and recovery operations; reduction of possible fire losses; improving the reliability of the fireproof beam during normal operation of the building and in a fire; simplification of the installation of frame elements and fire protection of the lining of the I-beam; increasing the rigidity of the joining beam with sheets and plates of the cladding and the resistance of the fire retardant cladding to mechanical stress; increasing the corrosion resistance of the steel beam and the maintainability of fire retardant cladding in case of local mechanical damage; reducing the complexity of mounting frame elements and fire retardant cladding elements; reduction in welding and wet construction processes.

The specified technical result when using the invention is achieved by the fact that in the known method of fire protection of an I-beam of a building, in which a sheet cladding is attached to the frame with steel reinforcing members of the beam, the feature is that the steel supporting rod is made in the form of a beam to which reinforcing elements of steel rolling profiles are fastened with holes with cut internal threads, in which set screws with countersunk heads are placed with a pointed and screwed-in pointed end, reinforcing elements of the beam I-beam are attached from below to the compressed and stretched shelves of the beam I-beam, to which elements of sheet and plate fire-retardant cladding are attached tightly with set screws; the thickness of the cladding elements is determined taking into account the thermal diffusion of its materials, the heating conditions of the beam and the standard limit of fire resistance of the building beam.

The reinforcement elements of the beam I-beam, located below the compressed and stretched shelves of the I-beam, are made in the form of two pairs of steel corners. The reinforcing element located at the bottom of the extended shelf of the beam I-beam is made in the form of a steel channel. The lining of the beam I-beam is performed in the form of a complex lining, including sheet and plate fire-retardant lining. The reinforcing elements of the beam I-beam are used as a frame for fastening the elements of the fire retardant lining. The thickness of the slab fire retardant cladding take at least the height of the shelves of the steel channel. The reinforcing elements are connected to the flanges of the I-beam by intermittent key welds of length l _w ≥50 mm with a pitch of dowels U ₁ ≤80 · r _min in the extended shelf and U ₂ ≤40 · r _min in the compressed shelf; here r _min is the radius of inertia of the angle and channel reinforcement, mm. Threaded holes in the frame elements for the set screws perform выполняют6 ÷ 20 mm in increments of 500 ÷ 1000 mm.

The thickness of the fire retardant cladding elements - δ _{o, mp} , mm, is determined by the exponential function (1):

$${\delta }_{o,mp}=0.7\cdot C\cdot D^{0.8}{}_{ar}/m_o,\left(\mathrm{one}\right)$$

where C is the degree of fire protection of the beam, cm;

D _ar is an indicator of thermal diffusion of the cladding material, mm ² / min;

m _o - an indicator of the heating conditions of the beam I-beam (0.5 ÷ 1).

The value of the fire protection limit of a single layer of the cladding - τ _{u, s} , min, is calculated by the exponential function (2):

$${\tau }_{u,co}=65\cdot m_{o\mathrm{one}}\cdot {\left({\delta }_{co}/D_{co}\right)}^{1.41},\left(2\right)$$

where m _o1 is an indicator of the heating conditions of the cladding layer (0.5 ÷ 1);

δ _co - the thickness of a single layer of fire retardant cladding, mm;

D _co - an indicator of thermal diffusion of the cladding layer, mm ² / min.

Fire protection of the I-beam of the building is carried out at positive and negative air temperatures.

The causal relationship between the totality of the features and the technical result of the invention is as follows: the use of the proposed method of fire protection of the I-beam of the building provides simplicity and reliability of fastening the elements of large-sized cladding and frame elements for it through the use of set screws with countersunk head with a long screwed pointed end and hard connection (welding) of the fixing nut to the shelves of the beam I-beam; a reduction in the mass of metal for the manufacture of carcass elements of the fire-retardant cladding is performed by reducing the number of carcass elements; reduction of the cross-sectional area of the fire-protected I-beam by 75 ÷ 95% due to the lack of void space between the steel supporting rod and the lining; increasing the fire resistance of a steel beam with a supporting rod in the form of a beam I-beam by 25 ÷ 35% due to the filling of the void space inside the cross section of the column; increasing the safety during extinguishing during emergency rescue and restoration operations, as well as reducing losses from a fire, is possible due to an increase in the fire resistance limits of the building's supporting structures; improving the reliability of the fire-protected beam during normal operation of the building and in fire conditions is possible due to increased rigidity in contact with the beam of I-beams with sheets and cladding plates, as well as designing the thickness of the cladding elements according to the proposed calculation method, depending on the fire resistance of the building, thermal diffusion of cladding materials and heating conditions of a beam I-beam in case of fire.

Figure 1 shows a cross section of a fire-protected I-beam with a contact connection of the elements of sheet and plate cladding to a steel supporting rod:

1 - beam I-beam; 2 - anti-corrosion layer; 3 - sheet fireproof lining; 4 - plate fireproof lining (for the wall of the I-beam); 5 - plate fireproof lining (for the lower flange of the I-beam); 6 - equal-shelf corner (on the upper flange of the I-beam, with a hole in the flange of the corner for the screw); 7 - unequal corner (on the lower flange of the I-beam, with a hole in the flange of the corner for the screw); 8 - weld (key, intermittent); 9 - set screws (with countersunk head with a screwed-in pointed end and a straight slot); 10 - fiberglass (plaster); 11 - adhesive layer (mortar); 12 - floor slab.

Figure 2 shows a cross-sectional diagram of a beam I-beam reinforced with equal-angled corners attached to the upper and lower shelves of the I-beam.

Figure 3 shows a cross section of a beam I-beam reinforced with equal-angled corners and a steel channel attached to the lower shelf of the I-beam: 13 - channel reinforcement (with holes in the shelves for screws), legend 1, 6 ÷ 9 and 12 are given in the description to figure 1).

Information confirming the possibility of applying the invention to obtain the above technical result

During the reconstruction of the university’s academic building, the project provides for fireproof steel beams from a rolling profile. Fire and technical characteristics of the building and its supporting beams: functional fire hazard class - F 4.2; degree of fire resistance - I (first); class of constructive fire hazard - СО (not fire hazardous); number of floors - 6; standard limit of fire resistance of the supporting beam F _u.n = 120 min (Table 21, Federal Law of the Russian Federation No. 123-2009); steel supporting rod - beam I-beam No. 20 B-1, the height of the I-beam h = 200 mm; shelf width b = 200 mm, wall thickness d = 6.5 mm; shelf thickness δ _s = 10 mm; the cross-sectional area of the I-beam A = 28.5 cm ² .

Fire protection of the lower flange of the I-beam - Rockwool mineral wool products M-50 mats; fire protection of the I-wall - mats M-50 with a thickness of δ _o , mm = b / 2 = 200/2 = 100 mm; plus sheet fireproof lining - refractory drywall sheet (GKLO) with a thickness of δ ₁ = 12.5 mm.

The required thickness of the elements of the fire retardant lining - δ _{o, mp} , mm, steel beam I-beam is determined by the exponential equation (1):

$${\delta }_{o.mp}=0.7\cdot C\cdot D^{0.8}{}_{ar}/m_o,$$

where C is the degree of fire protection of the beam, cm;

D _ar is an indicator of thermal diffusion of the cladding material, mm ² / min;

m _o - an indicator of the heating conditions of the beam I-beam (0.5 ÷ 1).

The degree of fire protection of a steel beam I-beam is calculated by the logarithmic equation (3):

$$C=In({\tau }_{uo}/48\cdot {\left(\mathrm{one}-J_{\sigma s}\right)}^3),\left(3\right)$$

when the intensity of power stresses J _σs = J _H = 0,625,

$$C=In(0.4\cdot {\tau }_{uo});\left(\mathrm{four}\right)$$

where C is the degree of fire protection of the beam, cm;

τ _uo - fire protection limit of cladding elements, min;

In is the natural logarithm.

The value of the limit of fire protection of the cladding is calculated by the algebraic formula (5):

$${\tau }_{uo}=F_{u,n}-{\tau }_{us};(5)$$

where F _{u, n} is the standard limit of fire resistance of the supporting beam, min;

τ _us - fire resistance of an I-beam without fire protection, min.

Example. Given: steel supporting rod - beam I-beam from rolling profile No. 20 B-1; standard limit of fire resistance of load-bearing beams for a building of I (first) degree of fire resistance F _{u, n} = 120 min (Table 21 of the Federal Law No. 123-2009); fire resistance of an I-beam without fire protection τz _us = 20 min; lining of the lower flange of the I-beam - rockwool M-50 mineral mats; thermal diffusion index - D _Roc = 68.8 mm ² / min; an indicator of the heating conditions of the I-wall m ₀₂ = 0.5; fire retardant wall cladding of the beam I-beam - refractory plasterboard sheets (GKLO), thermal diffusion index - D _GKLO = 20 mm ² / min; an indicator of the heating conditions of the I-beam shelves m ₀₁ = 0.75; plus mats from mineral wool M-50 with a thickness of δ _o , mm = b / 2 = 200/2 = 100 mm.

Determine the thickness of the elements of sheet and plate cladding.

Decision.

1) The limit of fire protection of the cladding is calculated by the algebraic formula (5):

. $${\tau }_{\text{u}}{}_{\text{î}}\text{-}={\text{F}}_{\text{u}\text{, n}}\text{-}{\tau }_{\text{us}}=\text{120-15}=\text{105 min}$$

.

2) The degree of fire protection of the beam I-beam complex lining (with J _σ = 0.625) is calculated by the logarithmic function (4):

С = In (0.4 · τ _uo ) = In (0.4 · 105) = In42 = 3.74 cm.

3) The required thickness of the fire-retardant cladding for the lower flange of the beam with Rockwool mineral wool in the form of M-50 mats (with an indicator of heating conditions m ₀₁ = 0.75) is determined by the exponential equation (1):

δ _mp , _mm = 0.7 · C · ^0.8 _mm / m ₀₂ = 0.7 · 3.74 · 68.8 ^0.8 / 0.75 = 103 mm> b / 2 = 200/2 =

= 100 mm; accepted δ _Roc = 100 mm.

4) The fire protection limit of the mat M-50 with a thickness of δ ₀ , _mm = 100 mm for the wall of the I-beam is determined by the exponential equation (2):

τ _{u, mm} = 65 · m ₀₂ · (δ ₀ , _mm / D _mm ) ^1.41 = 65 · 0.5 · (100 / 68.82) ^1.41 = 55 mm.

5) The total fire protection limit for the wall of the I-beam is:

Στ _uo = τ _u , _mm + τ _us = 55 + 15 = 70 min.

6) The required fire protection limit of the sheet cladding for the wall of the I-beam is τ _{uo, 2} = F _{u, n} -Στ _u = 120-70 = 50 min.

7) The degree of fire protection of the walls of the I-beam of the sheet cladding is calculated by the logarithmic function (4):

С = In (0.4 · τ _{uo, 2} ) = In (0.4 · 0) = 3.

8) The required thickness of the sheet of fire-retardant cladding for the wall of the beam I-beam refractory plasterboard sheets (with m ₀₁ = 1,0) is calculated by the exponential equation (1):

δ _{mp, GKLO} = 0.7 · C · D ^0.8 _GKLO / m ₀₁ = 0.7 · 3 · 20 ^0.8 / 1 = 23 mm.

9) The number of layers of wall cladding of the beam I-beam of refractory plasterboard sheets (thickness δ ₁ = 12.5 mm each sheet) is equal to:

n _GKLO = δ _{mp, GKLO} / δ ₁ = 23 / 12.5 = 1.84; accepted n _GKLO = 2 sheets on each side of the I-wall.

The structure of work on the fire protection method of an I-beam of a building includes: preparing the surface of a beam I-beam 1 and applying an anti-corrosion layer 2; selection of materials for fire retardant cladding; calculation of the thickness of the cladding elements; manufacturing elements of sheet fire retardant cladding 3, plate fire retardant cladding for wall 4 and plate fire retardant cladding for lower shelf 5; installation of reinforcement corners 6, 7 on the shelves of the beam I-beam 1; installation of the elements of sheet fire retardant cladding 3 and fixing them with set screws 9; applying an adhesive layer 11 to the surface of the wall and the shelves of the beam I-beam 1 and gluing to them the elements of the plate fire-retardant cladding for the wall 4 and the plate fire-retardant cladding for the lower shelf 5; screwing each set screw 9 with a countersunk head and with a pointed end into the elements of the plate cladding 4 and 5 to a depth of l _k > 0.2 · h (here h is the height of the column I-beam 1); coating the surface of the elements of fire retardant cladding with fiberglass 10 (if necessary).

The proposed method for the fire protection device of an I-beam of a building was used in the reconstruction of the educational building No. 2 of the SASAS (Samara, 2010/12).

Claims (11)

1. A method of fire protection of an I-beam of a building, in which a sheet cladding is attached to the frame using steel beam reinforcing elements to strengthen the beam, characterized in that the steel bearing rod is made in the form of a beam, to which reinforcement elements are made of steel rolling profiles with holes with a threaded internal thread, in which set screws with a countersunk head and a screwed-in pointed end are placed, reinforcing elements of the beam I-beam are attached from below with a compressed and astyanutoy I-beam flanges of the beam to which are attached close setscrews elements and the sheet of plate fireproof lining; the thickness of the cladding elements is determined taking into account the thermal diffusion of its materials, the heating conditions of the beam and the standard limit of fire resistance of the building beam. 2. The method according to claim 1, characterized in that the reinforcing elements of the beam I-beam, located below the compressed and extended shelves of the I-beam, are made in the form of two pairs of steel corners. 3. The method according to claim 1, characterized in that the reinforcing element located below the stretched shelf of the beam I-beam is made in the form of a steel channel. 4. The method according to claim 1, characterized in that the lining of the beam I-beam is made in the form of a complex lining, including sheet and plate fire retardant lining. 5. The method according to claim 1, characterized in that the reinforcing elements of the beam I-beam are used as a frame for fastening the elements of the fire retardant lining. 6. The method according to PP.1 and 3, characterized in that the thickness of the plate fire retardant cladding take at least the height of the shelves of the steel channel. 7. The method according to claim 1, characterized in that the reinforcing elements are connected to the flanges of the I-beam by intermittent key welds of a length l _w ≥50 mm with a pitch of dowels U ₁ ≤80 · r _min in the extended shelf and U ₂ ≤40 · r _min in a compressed shelf; here r _min is the radius of inertia of the angle and channel reinforcement, mm. 8. The method according to claim 1, characterized in that the threaded holes in the frame elements for the set screws perform ⌀6 ÷ 20 mm in increments of 500 ÷ 1000 mm. 9. The method according to claim 1, characterized in that the thickness of the elements of the fire retardant lining - δ _{o, mp} , mm, is determined by the exponential function (1):
δ _{o, mp} = 0.7 · C · D ^0.8 _ar / m _o ,
where C is the degree of fire protection of the beam, cm;
D _ar is an indicator of thermal diffusion of the cladding material, mm ² / min;
m _o - an indicator of the heating conditions of the beam I-beam (0.5 ÷ 1). 10. The method according to claim 1, characterized in that the value of the fire protection limit of an individual layer of the facing τ _{u, s} , min, is calculated by the exponential function (2):
τ _{u, co} = 65 m _o1 (δ _co / D _co ) ^1.41 ,
where m _o1 is an indicator of the heating conditions of the cladding layer (0.5 ÷ 1);
δ _co - the thickness of a single layer of fire retardant cladding, mm;
D _co - an indicator of thermal diffusion of the cladding layer, mm ² / min. 11. The method according to claim 1, characterized in that the fire protection of the I-beam of the building is carried out at positive and negative air temperatures.

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