RU2517313C1 - Fireproof double-tee beam of building - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: steel beam double tee, to which steel rolled profiles are fixed from a bar and a pair of angles, is equipped with fastening nuts and setting screws with hidden heads and a screwed-in sharpened end. The elements of the sheet lining are fixed tightly to the shelves of the beam double tee, elements of the tile lining - tightly to the double tee wall. Thickness of the elements of the fireproof lining is preliminarily defined with account of thermal properties of its materials and conditions of heating during fire.

EFFECT: increased reliability of fixation of elements of large-size lining, increased limit of steel beam fire resistance, reduced risk of beam damage in initial stage of fire.

8 cl, 3 dwg

Description

The invention relates to the field of fire safety of buildings and structures (hereinafter referred to as buildings). In particular, it can be used in the design and manufacture of structural fire protection of a steel beam supporting rod, 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.

The design of a fire-protected I-beam of a building is known, the lining of which is presented 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 / VIPPS, Editorial and Publishing Department. - 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) / [1].

The reasons that impede the achievement of the technical result indicated below when using the known design of a fire-protected I-beam include the fact that in the known design 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 a ceramic stone favors the rapid heating of the cladding to critical temperatures of heating a steel beam I-beam and a decrease in the fire limit capacity by 20 ÷ 25%; the building industry does not produce ceramic cladding cladding products; therefore, it is neither industrial nor economical.

A known design of a fire-protected I-beam of a building, containing a steel I-beam and fire-retardant cladding from large-sized sheets and plates mounted on a rel — the gap between the fire-retardant cladding and the faces of the protected steel supporting rod is adopted at least 25 mm; 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 were fastened to each other by self-tapping screws 5 × 25 ÷ 5 × 45 / Romanenkov I.G., Levites F.A. Fire protection of building structures. - M .: Stroyizdat, 1991 .-- 320 p. (Chapter 4 Structural methods of fire protection; Sec. 4.2 - Large-sized sheet, plate and roll cladding; Fig. 8, p.131-133) / [2].

The reasons that impede the achievement of the technical result indicated below when using the known design of the fireproof beam of the building include the fact that a significant number of frame elements are used in the known design and, as a result, the metal consumption for the manufacture of the frame 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 cladding, the cross-sectional dimensions of the lined beam increase (the cross-sectional area increases by 40–45%; the consumption of cladding 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 fireproof lining are reduced (if it is possible to obtain mechanical damage and through spalls).

The closest technical solution to the invention in terms of features is the construction of a fire-protected I-beam of a building, containing a steel supporting rod with anchors on its side faces, a frame made of C-shaped profiles, consisting of longitudinal elements with bends along the edges of the shelves and transverse elements, cladding 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 are facing ki flame retardancy in the cross section of the column is _empty A = 650 cm ²⁾ /A.s. SU 887755, MKI-3 Е04В 1/94. The building unit of the building / Yu.V. Pokrovsky, V.V. Fedorov, M.M.Karabochinsky and others; declared 02.21.80; publ. 12/12/81; Bull. No. 45 / [3] - taken as a prototype.

The reasons that impede the achievement of the technical result indicated below when using the known construction of a fireproof I-beam of a building include the fact that a significant number of carcass elements are used in the known construction 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 cladding, the cross-sectional dimensions of the lined beam increase (the cross-sectional area increases by 30–40%; the consumption of cladding materials by 30–35%); the design limit of fire resistance of the fireproof beam 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 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 reinforcing elements of a beam I-beam for it; reduction in the number of reinforcing elements of the beam for the flame retardant lining; 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 reinforcing elements of the beam I-beam 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 the reinforcement elements of the beam and the elements of fire retardant lining; reduction in welding and wet construction processes.

The specified technical result when using the invention is achieved by the fact that in the known construction of the fireproof I-beam of the building containing the supporting rod, reinforcing elements of the beam I-beam and sheet cladding, the feature is that the steel supporting rod is made in the form of a beam I-beam, to which reinforcing elements of steel rolling profiles with holes with threaded internal thread, in which are set screws with countersunk head and screwed-in pointed Tzom, strengthening elements are attached below the compressed and stretched flange beam I-beam to which the set screws are fastened into a dense sheet elements and the flame-retardant of plate lining; the thickness of the cladding elements is determined taking into account the thermal diffusion of its materials, the heating conditions of the beam I-beam and the standard limit of fire resistance of the building beam.

Other features is that the reinforcement elements of the beam I-beam, located below the compressed and stretched shelves of the beam I-beam, are made in the form of two pairs of steel corners. The reinforcement element of the beam I-beam, located at the bottom of the extended shelf of the beam I-beam, is made in the form of a steel channel. The thickness of the flame retardant cladding is accepted not less than the height of the shelves of the steel channel. The reinforcing elements of the beam I-beam are connected to the shelves of the beam 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 inertia of a corner or channel, cm). The threaded holes in the reinforcing elements of the beam I-beam for the set screws are made ⌀ 6 ÷ 20 mm in increments of 500 ÷ 1000 mm.

The thickness of the elements of the fire retardant lining -δ _{о, mp} , mm, is determined by the exponential equation (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, calculated by the exponential equation (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.

The causal relationship between the totality of the features and the technical result of the invention is as follows: the use of the proposed design of a fire-protected I-beam of the building provides the 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 a 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), designations pos. 1, 6 - 9 and 12 are given in the description of 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 (non-fire hazardous); number of floors - 6; standard limit of fire resistance of the supporting beam F _{u, mp} = 120 min (Table 21, Federal Law of the Russian Federation No. 123-2009); steel supporting rod - beam I-beam No. 20B-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 products, mats M-50; fire protection of the I-wall - mats M-50 with a thickness of δ _о , 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 _{о, mp} , mm, steel beam I-beam is determined by the exponential equation (I):

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

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

D _ar - 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 (0.25 ÷ 1).

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

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

(3) at the intensity of power stresses J _σs = 0.625,

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

where C is the degree of fire protection of the beam I-beam;

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):

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

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

τ _us is the fire resistance limit of the beam with no flame retardant lining, min.

Example: given: steel supporting rod - beam I-beam from a 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 Federal Law No. 123-2009); the fire resistance of the beam without a flame retardant facing τ _us = 20 min; lining of the lower flange of the I-beam - M-50 mineral wool mats, Rockwool products; 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):

τ _uo = F _{u, n} -τ _us = 120-15 = 105 min.

2) The degree of fire protection of the beam I-beam with complex lining (with J _σs = 0.625) was calculated according to the exponential equation (4):

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

3) The required thickness of the slab fire retardant cladding for the bottom

shelves of a beam I-beam with Rockwool mineral wool products 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 · D ^0.8 _mm / m ₀₂ = 0.7 · 3.74 · 68.8 ^0.8 / 0.75 = 103 mm> b / 2 = 200/2 = 100 mm, taken δ _Roc = 100 mm.

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

τ _{u, mm} = 65 · m ₀₂ · (δ _{o, 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:

∑τ _u = 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} -∑τ _u = 120-70 = 50 min.

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

C = In (0.4 · τ _uo , ₂ ) = In (0.4 · 05) = 3.

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

t _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 the fire protection device of the I-beam of the building includes: preparing the surface of the 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; manufacture of elements of sheet fireproof cladding - 3 and plate fireproof cladding for the wall - 4 and plate fireproof cladding for the lower shelf - 5; installation of reinforcement angles on the shelves of the beam I-beam - 1; installation of elements of sheet fire retardant cladding - 3 and fastening them with set screws - 9; applying an adhesive layer - 11 to the surface of the wall and 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 in each set screw - 9 with a countersunk head and with a pointed end into the elements of plate cladding - 4 and 5 to a depth of l _to ≥0.2 · h (here h is the height of the column I-beam - 1); coating the surface of the elements of fire-retardant plate cladding for the wall - 4 and plate fire-retardant cladding for the lower shelf - 5 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).

Information sources

1. Roytman M.Ya. Fire prevention in the construction industry / VIPPSH, RIO. - M., 1975 .-- 525 p. (Ch.5 Fire protection of metal structures; §5.2. Improving the fire resistance of steel structures; Fig.5.2 (6), p.116-117).

2. Romanenkov I.G., Levites F.A. Fire protection of building structures. - M .: Stroyizdat, 1991. - 320 p. (Chap. 4 Structural methods of fire protection; Sec. 4.2. - Large-sized sheet, plate and roll cladding; Fig. 8, pp. 131-133).

3. A.S. SU No. 887755, MKI-3 Е04В 1/94, Building unit of the building / Yu.V. Pokrovsky, V.V. Fedorov, M.M.Karabochinsky and others; declared 02.21.80; publ. 12/07/81, Bull. No. 45.

Claims (8)

1. Fire-protected I-beam of a building containing a steel supporting rod, reinforcing elements of the beam I-beam and sheet cladding attached to the beam frame, characterized in that the steel supporting rod is made in the form of a beam, to which reinforcing elements are made of steel rolling profiles with holes with threaded internal thread, in which are set screws with countersunk head and screwed-in pointed end, reinforcing elements are attached to the bottom of the compressed and extended ball shelves full-time I-beam, to which the installation screws are attached closely to the elements of sheet and plate fire-retardant lining; the thickness of the cladding elements is determined taking into account the thermal diffusion of its materials, the heating conditions of the beam I-beam and the standard limit of fire resistance of the building beam. 2. Fireproof beam according to claim 1, characterized in that the reinforcing elements of the beam I-beams located below the compressed and stretched shelves of the beam I-beams are made in the form of two pairs of steel corners. 3. The fireproof beam according to claim 1, characterized in that the reinforcing member of the beam I-beam, located below the extended shelf of the beam I-beam, is made in the form of a steel channel. 4. Fireproof beam according to claims 1 and 3, characterized in that the thickness of the fire-retardant plate cladding is adopted not less than the height of the shelves of the steel channel. 5. Fireproof beam according to claim 1, characterized in that the reinforcing elements of the beam I-beam are connected to the shelves of the beam I-beam by intermittent key welds with a length of 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 a corner or channel, see 6. Fireproof beam according to claim 1, characterized in that the threaded holes in the reinforcing elements of the beam I-beams for the set screws are made ⌀ 6 ÷ 20 mm in increments of 500 ÷ 1000 mm. 7. Fireproof beam according to claim 1, characterized in that the thickness of the elements of the fireproof lining - δ _{о, mp} , mm, is determined by the exponential equation (1):

,
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). 8. Fireproof beam according to claim 1, characterized in that the value of the fire protection limit of a single layer of the cladding is τ _{u, s} , min, calculated by the exponential equation (2):

,
where m ₀₁ 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.

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