A guide for determining the limits of fire resistance of building structures. Fire resistance of metal structures

The essence of the calculation method

The purpose of the calculation is the definition of the time after which the building structure under standard temperature conditions will lose (will exhaust) its load-bearing or thermal insulation capacity (1 and 3 limit states of structures for fire resistance), that is, before the time of the onset of P f.

The onset time (P f) for the second limiting state of the structure in terms of fire resistance cannot yet be calculated.

According to the 3 limit state of the structure for fire resistance, internal walls, partitions, and ceilings are calculated.

Considering that individual structures are both load-bearing and fencing, they are calculated according to 1 and 3 limit states for fire resistance, for example: structures of internal load-bearing walls, floors.

The same applies to the determination of the fire resistance of structures and according to the reference manual, technical information ("To help the GPN inspector") and, naturally, by the method of full-scale fire tests.

In the general case, the method for calculating the fire resistance of a load-bearing building structure consists of from heat engineering and static parts (enclosing - only from heat engineering).

Heat engineering part calculation methodology provides for the determination of temperature changes (during exposure to standard temperature conditions) as at any point along the thickness of the structure, as well as its surfaces.

Based on the results of such a calculation, it is possible to determine not only the indicated temperature values, but also the heating time of the enclosing structure to the limiting temperatures (140 ° C + t n), that is, the time of the onset of its fire resistance limit according to the 3 limiting state of the structure in terms of fire resistance.

Static part the methodology provides for the calculation of the change in bearing capacity (by strength, amount of deformation) heated structure during a standard fire test.

Calculation schemes

When calculating the fire resistance of a structure, the following design schemes are usually used:

The 1st design scheme (Fig. 3.1) is used when the fire resistance limit of the structure occurs as a result of the loss of its heat-insulating ability (3rd limit state for fire resistance). The calculation on it is reduced to solving only the heat engineering part of the fire resistance problem.

Rice. 3.1. The first calculation scheme. a - vertical fence; b - horizontal fence.

The 2nd design scheme (Fig. 3.2) is used when the fire resistance of the structure occurs as a result of the loss of its bearing capacity (when heated above the critical temperature - t cr of metal structures or working reinforcement of a reinforced concrete structure).

Rice. 3.2. The second calculation scheme. a - lined metal column; b - frame metal wall; в - reinforced concrete wall; d - reinforced concrete beam.

Critical - temperature - t cr bearing metal structure or working reinforcement of a bent reinforced concrete structure - the temperature of its heating, at which the yield point of the metal, decreasing, reaches the value of the standard (working) stress from the standard (working) load on the structure, respectively.

Its numerical value depends on the composition (stamps) metal, processing technology of the product and the size of the normative (worker - the one that operates in the constructed building) load on the structure. The slower the metal's yield point decreases during heating and the lower the value of the external load on the structure, the higher the value of t cr, i.e., the higher the P f of the structure.

There are structures, in particular, wooden ones, the destruction of which in a fire occurs as a result of a decrease in their cross-sectional area to a critical value - F cr when wood is charred.

As a result of this, the voltage value is s from the external load in the remaining (working) part of the cross-section of the structure increases, and when this value reaches the value of the standard resistance - R nt wood (corrected for temperature value) the structure collapses, because its fire resistance limit occurs (loss of bearing capacity), i.e., P f. For this case, 3 design scheme is used.

Calculation of the actual limit of fire resistance of the structure according to 3rd design scheme is reduced to determining the time point of the standard design fire resistance test, upon reaching which (at a known wood charring rate - n l) cross-sectional area - S structure (its bearing part) will decrease to a critical value.

Rice. 3.3. Third calculation scheme. a - wooden beam; b - reinforced concrete column.

According to this design scheme, also with a result sufficient for practical purposes, it is possible to calculate the actual fire resistance of the bearing reinforced concrete structure of the column, assuming that the standard resistance (tensile strength) of concrete heated above the critical temperature is equal to zero, and within the critical area of the "cross-section" is equal to the initial value - R n.

With the use of a computer appeared 4 design scheme, which provides, simultaneously with the solution of the thermotechnical part of the fire resistance problem, the calculation and changes in the bearing capacity of the structure before its loss (i.e., before the onset of P f of the structure according to the first limiting state of fire resistance - Fig. 3.5), when:

N t N n; or M t = M n. (3.1)

where N t; M t is the bearing capacity of the heated structure, N; H × m;

N n; M n - standard load (moment from the standard load on the structure) N, N × m.

According to this design scheme, the temperature is calculated using a PC at each point of the computational grid (Figure 3.5), superimposed on the cross-section of the structure, at design time intervals (good convergence of the calculation results with the results of full-scale fire tests - with a counting step D t £ 0.1 min).

Simultaneously with the calculation of the temperature at each point of the computational grid, the PC also calculates the strength of the material at these points - at the same times - at the corresponding temperatures (that is, it solves the static part of the fire resistance problem). At the same time, the PC sums up the strength indicators of the construction materials at the points of the computational grid and thus determines the total bearing capacity, that is, the bearing capacity of the structure as a whole at a given point in time for the standard fire resistance test of the structure.

Based on the results of such calculations, a graph of changes in the bearing capacity of the structure from the time of the fire test (Figure 3.4) is built manually (or using a PC), according to which the actual fire resistance of the structure is determined.

Rice. 3.4. Change (decrease) in the bearing capacity of a structure (for example, a column) to the standard load when it is heated under conditions of full-scale fire tests.

Thus, 2 and 3 design schemes are special cases of the 4th.

As already mentioned, building structures that perform both the supporting and enclosing functions are calculated according to the 1st and 3rd limiting states of the structure in terms of fire resistance. In this case, the 1st calculation scheme, as well as the 2nd, are used, respectively. An example of such a design is ribbed w / b a floor slab, for which, according to the first design scheme, the time of the onset of the third limiting state of the structure in terms of fire resistance is calculated - when the shelf warms up. Then the time of the onset of the 1st limiting state of the structure in terms of fire resistance is calculated - as a result of heating the working reinforcement of the slab to - t cr - according to the 2nd design diagram - until the destruction of the slab due to a decrease in its bearing capacity (working reinforcement in ribs) before the normative (working) load.

Due to the insufficiency of the results of experimental and theoretical studies, the following basic assumptions are usually introduced into the methodology for calculating the limits of fire resistance of structures:

1) a separate structure is subjected to the calculation - without taking into account its connections (articulation) with other structures;

2) a vertical rod structure during a fire (full-scale fire test) warms up evenly over the entire height;

3) there is no heat leakage along the ends of the structure;

4) thermal stresses in the structure, resulting from its uneven heating (due to a change in the deformative properties of materials and various values of the thermal expansion of the layers of the material), absent.

Art. Lecturer of the Department of PBZiASP

Art. Lieutenant of the internal service G.L. Shidlovsky

”______” _______________ 201_ year

Similar information.

. .

Limitfire resistance of the structure- the time interval from the start of fire exposure under standard test conditions to the onset of one of the limit states normalized for a given design.

For load-bearing steel structures, the limiting state is the bearing capacity, that is, the indicator R.

Although metal (steel) structures are made of non-combustible materials, the actual fire resistance is on average 15 minutes. This is due to a fairly rapid decrease in the strength and deformation characteristics of the metal at elevated temperatures during a fire. The heating intensity of the MC depends on a number of factors, which include the nature of the heating of the structures and the methods of their protection.

There are several temperature regimes of fire:

Standard fire;

Tunnel fire mode;

Hydrocarbon fire mode;

External fire modes, etc.

When determining the limits of fire resistance, a standard temperature regime is created, characterized by the following relationship

where T- temperature in the furnace corresponding to the time t, deg C;

That- the temperature in the furnace before the start of the thermal effect (taken equal to the ambient temperature), deg. WITH;

t- time calculated from the beginning of the test, min.

The temperature regime of a hydrocarbon fire is expressed by the following relationship

The onset of the fire resistance limit of metal structures occurs as a result of loss of strength or due to loss of stability of the structures themselves or their elements. Both cases correspond to a certain heating temperature of the metal, which is called critical, i.e. at which the formation of a plastic hinge occurs.

Calculation of the fire resistance limit is reduced to solving two problems:static and heat engineering.

The static problem is aimed at determining the bearing capacity of structures taking into account changes in metal properties at high temperatures, i.e. determining the critical temperature at the time of the onset of the limiting state in case of fire.

As a result of solving the heat engineering problem, the time of heating the metal from the start of the fire until reaching the critical temperature in the design section is determined, i.e. the solution of this problem allows you to determine the actual limit of fire resistance of the structure.

The fundamentals of modern calculation of the fire resistance of steel structures are presented in the book "Fire resistance of building structures" * I.L. Mosalkov, G.F. Plyusnina, A. Yu. Frolov Moscow, 2001 Special equipment), where section 3 on pages 105-179 is devoted to the calculation of the fire resistance of steel structures.

The method for calculating the limits of fire resistance of steel structures with fire retardant coatings is set out in the VNIIPO Methodological Recommendations "Fire protection means for steel structures. Calculation and expert method for determining the fire resistance limit of load-bearing metal structures with thin-layer fire-retardant coatings".

The result of the calculation is a conclusion about the actual limit of fire resistance of the structure, including taking into account solutions for its fire protection.

To solve a heat engineering problem, i.e. tasks in which it is necessary to determine the heating time of the structure to the critical temperature, it is necessary to know the calculated loading scheme, the reduced thickness of the metal structure, the number of heated sides, steel grade, cross-sections (moment resistance), as well as the heat-shielding properties of fire retardant coatings.

The effectiveness of fire protection means for steel structures is determined in accordance with GOST R 53295-2009 "Fire protection means for steel structures. General requirements. Method for determining fire protection efficiency". Unfortunately, this standard cannot be used to determine the limits of fire resistance, this is directly written in clause 1 "Scope":" Real the standard does not cover the definition limitsfire resistance of building structures with fire protection ".

The fact is that according to GOST, as a result of tests, the time for warming up the structure to a conditionally critical temperature of 500C is established, while the calculated critical temperature depends on the "safety factor" of the structure and its value can be either less than 500C or more.

Abroad, fire protection means are tested for fire retardant efficiency upon reaching a critical temperature of 250C, 300C, 350C, 400C, 450C, 500C, 550C, 600C, 650C, 700C, 750C.

The required fire resistance limits are established by Art. 87 and Table No. 21 of the Technical Regulations on Fire Safety Requirements.

The degree of fire resistance is determined in accordance with the requirements of SP 2.13130.2012 "Fire protection systems. Ensuring fire resistance of protected objects".

In accordance with the requirements of clause 5.4.3 SP 2.13130.2012 .... allowed use unprotected steel structures, regardless of their actual fire resistance limit, except for cases when the fire resistance limit of at least one of the supporting structure elements (structural elements of trusses, beams, columns, etc.) is less than R 8 according to the test results. Here, the actual fire resistance limit is determined by calculation.

In addition, the same paragraph restricts the use of thin-layer fire-retardant coatings (fire-retardant paints) for load-bearing structures with a reduced metal thickness of 5.8 mm or less in buildings of I and II degrees of fire resistance.

Load-bearing steel structures are, in most cases, elements of the frame-tie frame of the building, the stability of which depends both on the fire resistance limit of the load-bearing columns and on the elements of the covering, beams and ties.

In accordance with the requirements of clause 5.4.2 SP 2.13130.2012 "The load-bearing elements of buildings include load-bearing walls, columns, braces, stiffening diaphragms, trusses, elements of floors and non-attic roofings (beams, crossbars, slabs, decks), if they are involved in providing a general sustainability and the geometric invariability of the building in the event of a fire. Information about the supporting structures that are not involved in providing the overall sustainabilityand the geometric immutability of the building, are given by the design organization in the technical documentation for the building".

Thus, all elements of the frame-tie frame of the building must have a fire resistance limit for the largest of them.

TsNIISK them. Kucherenko of the USSR State Construction Committee

to determine the limits of fire resistance of structures, the limits of the spread of fire over structures and groups

flammability of materials

(kSNiP II-2-80)

Moscow 1985

ORDER OF LABOR RED BANNER CENTRAL RESEARCH INSTITUTE OF BUILDING CONSTRUCTIONS them. V. A. KUCHERENKO SCHNIISK nm. Kucherenko) GOSSTROYA USSR

FOR DETERMINING THE LIMITS OF FIRE RESISTANCE OF A STRUCTURE,

LIMITS OF SPREADING OF FIRE ON STRUCTURES AND GROUPS

FLAMMABILITY OF MATERIALS (TO SNiP I-2-80)

Approved by

A guide for determining the limits of fire resistance of structures, the limits of the spread of fire on structures and groups of flammability of materials (to SNiP II-2-80) / TsNIISK nm. Kucherenko.- M .: Stroyizdat, 1985.-56 p.

Developed for SNiP 11-2-80 "Fire safety standards for the design of buildings and structures." Provides reference data on the limits of fire resistance and fire propagation on building structures made of reinforced concrete, metal, wood, asbestos cement, plastics and other building materials, as well as data on the flammability groups of building materials.

For engineering and technical workers of design, construction organizations and bodies of state fire supervision.

Tab. 15, fig. 3.

3206000000-615 047(01)-85

Instruction-norm. (I issue - 62-84

FOREWORD

This Manual was developed for SNiP 11-2-80 "Fire safety standards for the design of buildings and structures." It contains data on the standardized indicators of fire resistance and fire hazard of building structures and materials.

Sec. I of the manual was developed by TsNIISK them. Kucherenko (Doctor of Technical Sciences, Prof. I. G. Romanenkov, Candidate of Technical Sciences V. N. Siegern-Korn). Sec. 2 developed by TsNIISK them. Kucherenko (Doctor of Technical Sciences I. G. Romanenkov, Candidates of Technical Sciences V. N. Siegern-Korn, L. N. Bruskova, G. M. Kirpichenkov, V. A. Orlov, V. V. Sorokin, engineers A. V. Pestritsky, | V. Y. Yashin |); NIIZhB (Doctor of Technical Sciences V.V. Zhukov; Doctor of Technical Sciences, Prof. A.F. Milovanov; Candidate of Physical and Mathematical Sciences A.E. Segalov, Candidates of Technical Sciences. A. Gusev, V. V. Solomonov, V. M. Samoilenko; engineers V. F. Gulyaeva, T. N. Malkina); TsNIIEP them. Mezentseva (candidate of technical sciences L. M. Schmidt, engineer P. Ye. Zhavoronkov); TsNIIPromzdanny (Candidate of Engineering Sciences V.V. Fedorov, engineers E.S. Giller, V.V. Sipin) and VNIIPO (Doctor of Technical Sciences, Prof. A.I. P. Bushev, S. V. Davydov, V. G. Olimpiev, N. F. Gavrikov; engineers V. 3. Volokhatykh, Yu. A. Grinchnk, N. P. Savkin, A. N. Sorokin, V. S. Kharitonov, L. V. Sheinina, V. I. Shchelkunov). Sec. 3 developed by TsNIISK them. Kucherenko (Doctor of Engineering Science, Prof. I. G. Romanenkov, Candidate of Chemistry N. V. Kovyrshina, Engineer V. G. Gonchar) and the Institute of Mining Mechanics of the Academy of Sciences of Georgia. SSR (Candidate of Technical Sciences G. S. Abashidze, engineers L. I. Mirashvili, L. V. Gurchumelia).

When developing the Manual, materials from TsNIIEP of housing and TsNIIEP of educational buildings of Gosgrazhdanstroy, MIIT of the USSR Ministry of Railways, VNIISTROM and NIPIsilikatobeton of the USSR Ministry of Industry and Construction were used.

The text of SNiP II-2-80 used in the Guide is typed in bold. Its items are double numbered, in parentheses the SNiP numbering is given.

In cases where the information given in the Manual is insufficient to establish the appropriate indicators of structures and materials, you should contact TsNIISK im. Kucherenko or NIIZhB Gosstroy of the USSR. The basis for establishing these indicators can also be the results of tests carried out in accordance with the standards and methods approved or agreed by the USSR State Construction Committee.

Comments and suggestions on the Manual, please send to the address: Moscow, 109389, 2nd Institutskaya st., 6, TsNIISK im. V.A.Kucherenko.

1. GENERAL PROVISIONS

1.1. The manual was compiled to help design, construction * # organizations and fire protection authorities in order to reduce the cost of time, labor and materials to establish the limits of fire resistance of building structures, the limits of the spread of fire along them and the flammability groups of materials, standardized by SNiP II-2-80.

1.2. (2.1). Buildings and structures are subdivided into five degrees of fire resistance. The degree of fire resistance of buildings and structures is determined by the limits of fire resistance of the main building structures and the limits of fire propagation along these structures.

1.3. (2.4). According to their flammability, building materials are divided into three groups: non-combustible, hardly combustible and combustible.

1.4. The limits of fire resistance of structures, the limits of fire propagation along them, as well as the groups of flammability of materials given in this Manual, should be included in the designs of structures, provided that their design fully complies with the description given in the Manual. The materials of the Manual should also be used when developing new designs.

2. BUILDING CONSTRUCTIONS.

FIRE RESISTANCE LIMITS AND FIRE SPREAD LIMITS

2.1 (2.3). The limits of fire resistance of building structures are determined according to the standard CMEA 1000-78 “Fire safety standards for building design. Method for testing building structures for fire resistance ".

The limit of spread of fire on building structures is determined according to the method given in Appendix. 2.

FIRE RESISTANCE LIMIT

2.2. The time (in hours or minutes) from the beginning of their standard fire test to the occurrence of one of the fire resistance limit states is taken as the fire resistance limit of building structures.

2.3. The CMEA 1000-78 standard distinguishes the following four types of limit states for fire resistance: for the loss of the bearing capacity of structures and assemblies (collapse or deflection, depending on the type

designs); in terms of thermal insulation capacity - an increase in temperature on an unheated surface by an average of more than 160 ° C or at any point on this surface by more than 190 ° C in comparison with the temperature of the structure before the test, or more than 220 ° C regardless of the temperature of the structure before the test; by density - the formation of through cracks or through holes in structures through which combustion products or flame penetrate; for structures protected by fire retardant coatings and tested without loads, the limiting state will be the achievement of the critical temperature of the material of the structure.

For exterior walls, coverings, beams, trusses, columns and pillars, the limiting state is only the loss of the bearing capacity of structures and assemblies.

2.4. The limiting states of structures in terms of fire resistance, indicated in clause 2.3, hereinafter for brevity will be called I, 11, 111 and IV, respectively, the limiting states of a structure in terms of fire resistance.

In cases of determining the limit of fire resistance under loads determined on the basis of a detailed analysis of the conditions that occur during a fire and differ from the normative ones, the limiting state of the structure will be denoted 1A.

2.5. The limits of fire resistance of structures can also be determined by calculation. In these cases, the tests are allowed not to be carried out.

The determination of the fire resistance limits by calculation should be carried out according to the methods approved by the Glavtekhnormirovanie Gosstroy of the USSR.

2.6. For an approximate assessment of the fire resistance of structures in their development and design, the following provisions can be followed:

a) the fire resistance limit of laminated enclosing structures in terms of thermal insulation capacity is equal, and, as a rule, higher than the sum of the fire resistance limits of individual layers. It follows from this that an increase in the number of layers of the enclosing structure (plastering, cladding) does not reduce its fire resistance limit in terms of thermal insulation capacity. In some cases, the introduction of an additional layer may not give an effect, for example, when cladding with sheet metal from the unheated side;

b) the fire resistance limits of enclosing structures with an air gap are on average 10% higher than the fire resistance limits of the same structures, but without an air gap; the efficiency of the air gap is the higher, the more it is removed from the heated plane; with closed air spaces, their thickness does not affect the fire resistance limit;

c) the limits of fire resistance of enclosing structures with asymmetry

The typical arrangement of the layers depends on the direction of the heat flux. On the side where the likelihood of a fire is higher, it is recommended to place non-combustible materials with low thermal conductivity;

d) an increase in the moisture content of structures contributes to a decrease in the heating rate and an increase in fire resistance, with the exception of those cases when an increase in moisture increases the likelihood of sudden brittle destruction of the material or the appearance of local gouges, this phenomenon is especially dangerous for concrete and asbestos-cement structures;

e) the fire resistance limit of loaded structures decreases with increasing load. The most stressed section of structures exposed to fire and high temperatures, as a rule, determines the value of the fire resistance limit;

f) the fire resistance limit of the structure is the higher, the smaller is the ratio of the heated perimeter of the section of its elements to their area;

g) the fire resistance limit of statically indeterminate structures, as a rule, is higher than the fire resistance limit of similar statically definable structures due to the redistribution of efforts to elements that are less stressed and heated at a lower speed; in this case, it is necessary to take into account the influence of additional efforts arising from temperature deformations;

h) the flammability of the materials from which the structure is made does not determine its fire resistance limit. For example, structures made of thin-walled metal profiles have a minimum fire resistance limit, and wood structures have a higher fire resistance limit than steel structures with the same ratios of the heated section perimeter to its area and the magnitude of the acting stresses to ultimate resistance or yield strength. At the same time, it should be borne in mind that the use of combustible materials instead of hardly combustible or non-combustible can lower the fire resistance of the structure if the rate of its burnout is higher than the heating rate.

To assess the limit of fire resistance of structures on the basis of the above provisions, it is necessary to have sufficient information about the limits of fire resistance of structures similar to those considered in form, materials used and design, as well as information about the basic laws of their behavior in case of fire or fire tests.

2.7. In cases where table. 2-15 fire resistance limits are indicated for structures of the same type of various sizes, the fire resistance limit of a structure having an intermediate size can be determined by linear interpolation. For reinforced concrete structures, interpolation should also be carried out in terms of the distance to the reinforcement axis.

FIRE SPREAD LIMIT

2.8. (Appendix 2, p. 1). The test of building structures for the spread of fire consists in determining the size of the damage to the structure due to its combustion outside the heating zone - in the control zone.

2.9. Damage is defined as visually detectable charring or burnout of materials and melting of thermoplastic materials.

For the limit of fire propagation, the maximum size of damage (cm) is taken, determined by the test methodology set forth in Appendix. 2 to SNiP II-2-80.

2.10. Structures made with the use of combustible and hardly combustible materials, as a rule, without finishing and cladding, are tested for the spread of fire.

Structures made only of non-combustible materials should be considered non-spreading fire (the limit of fire spreading along them should be taken equal to zero).

If, during the test for the spread of fire, damage to structures in the control area is not more than 5 cm, it should also be considered non-spreading fire.

2.11: The following provisions can be used for a preliminary estimate of the limit of spread of fire:

a) structures made of combustible materials have a limit for the spread of fire horizontally (for horizontal structures - floors, coverings, beams, etc.) more than 25 cm, and vertically (for vertical structures - walls, partitions, columns, etc. . and.) - more than 40 cm;

b) structures made of combustible or hardly combustible materials, protected from the effects of fire and high temperatures by non-combustible materials, can have a limit of fire propagation horizontally less than 25 cm, and vertically - less than 40 cm, provided that the protective layer during the entire test period (until the structure has completely cooled down) does not warm up in the control zone to the ignition temperature or the beginning of intensive thermal decomposition of the protected material. The structure may not spread fire, provided that the outer layer, made of non-combustible materials, during the entire test period (until the structure has completely cooled down) does not warm up in the heating zone to the ignition temperature or the beginning of intensive thermal decomposition of the protected material;

c) in cases where the structure can have a different limit of fire propagation when heated from different sides (for example, with an asymmetric arrangement of layers in the enclosing structure), this limit is established by its maximum value.

CONCRETE AND REINFORCED CONCRETE STRUCTURES

2.12. The main parameters that affect the fire resistance of concrete and reinforced concrete structures are: type of concrete, binder and aggregate; reinforcement class; type of construction; cross-sectional shape; element sizes; the conditions for their heating; load value and moisture content of concrete.

2.13. The increase in temperature in the concrete of the section of an element during a fire depends on the type of concrete, binder and aggregates, on the ratio of the surface on which the flame acts to the cross-sectional area. Heavy concrete with silicate aggregate heats up faster than carbonate aggregate. Lightweight and lightweight concretes heat up the slower, the lower their density. The polymer bond, like the carbonate filler, reduces the rate of concrete heating due to the decomposition reactions occurring in them, which consume heat.

Massive structural elements better resist the effects of fire; the fire resistance limit of columns heated from four sides is less than the fire resistance limit of the columns with one-sided heating; the fire resistance limit of beams when exposed to fire from three sides is less than the fire resistance limit of beams heated from one side.

2.14. The minimum dimensions of elements and distances from the axis of the reinforcement to the surfaces of the element are taken according to the tables of this section, but not less than those required by the chapter of SNiP I-21-75 "Concrete and reinforced concrete structures".

2.15. The distance to the axis of the reinforcement and the minimum dimensions of the elements to ensure the required limit of fire resistance of structures depend on the type of concrete. Lightweight concretes have a thermal conductivity of 10-20%, and concretes with coarse carbonate aggregate are 5-10% less than heavy concretes with silicate aggregates. In this regard, the distance to the axis of the reinforcement for a structure made of lightweight concrete or heavy concrete with a carbonate filler can be taken less than for structures made of heavy concrete with silicate aggregate with the same fire resistance limit of structures cast from these concretes.

The values of the fire resistance limits given in table. 2-b, 8, refer to concrete with a large aggregate of silicate rocks, as well as to dense silicate concrete. When using filler from carbonate rocks, the minimum dimensions of both the cross-section and the distance from the axes of the reinforcement to the surface of the bent element can be reduced by 10%. For lightweight concrete, the reduction can be 20% at a concrete density of 1.2 t / m 3 and by 30% for bending elements (see tables 3, 5, 6, 8) at a concrete density of 0.8 t / m 3 and expanded clay perlite concrete with a density of 1.2 t / m 3.

2.16. During a fire, a protective layer of concrete protects the reinforcement from rapid heating and reaching its critical temperature, at which the fire resistance of the structure is reached.

If the distance to the axis of the reinforcement adopted in the project is less than that required to ensure the required limit of fire resistance of structures, it should be increased or additional heat-insulating coatings should be applied on the surfaces of element 1 exposed to fire. Thermal insulation coating of lime-cement plaster (15 mm thick), gypsum plaster (10 mm) and vermiculite plaster or mineral fiber insulation (5 mm) are equivalent to a 10 mm increase in the thickness of the heavy concrete layer. If the thickness of the concrete cover is more than 40 mm for heavy concrete and 60 mm for lightweight concrete, the concrete cover must have additional reinforcement on the fire side in the form of a mesh of reinforcement with a diameter of 2.5-3 mm (cells 150X150 mm). Protective heat-insulating coatings with a thickness of more than 40 mm must also have additional reinforcement.

Table 2, 4-8 show the distances from the heated surface to the axis of the reinforcement (Fig. 1 and 2).

Rice. 1. Distances to the axis of the reinforcement Fig. 2. Average distance to the axis *

fittings

In cases where the reinforcement is located at different levels, the average distance to the axis of the reinforcement a should be determined taking into account the areas of the reinforcement (Лг, ..., Лп) and the corresponding distances to the axes (ob a-1 ..... Qn), measured from the nearest of the heating

myh (bottom or side) surfaces of the element, according to the formula

... ... ... ,. „2 Ai a (

L | 0 | -j ~ LdOr ~ f ~ ■. ... + A p a p __ j ° i_

P1 + L2 + P3,. + L Z 2 Ai

2.17. All steels reduce tensile or compressive resistance

1 Additional heat-insulating coatings can be performed in accordance with the "Recommendations for the use of fire-retardant coatings for metal structures" - M .; Stroyizdat, 1984.

when heated. The degree of resistance reduction is greater for hardened high-strength rebar steel than for low-carbon steel bar rebar.

The fire resistance limit of elements bent and eccentrically compressed with a large eccentricity in terms of loss of bearing capacity depends on the critical heating temperature of the reinforcement. The critical heating temperature of the reinforcement is the temperature at which the tensile or compressive resistance decreases to the value of the stress arising in the reinforcement from the standard load.

2.18. Tab. 5-8 are compiled for reinforced concrete elements with non-tensioned and pre-stressed reinforcement on the assumption that the critical heating temperature of the reinforcement is 500 ° C. This corresponds to reinforcing steels of classes A-I, A-H, A-1v, A-Shv, A-IV, At-IV, A-V, At-V. The difference in critical temperatures for other classes of reinforcement should be taken into account by multiplying those given in table. 5-8 fire resistance limits per coefficient<р, или деля приведенные в табл. 5-8 расстояния до осей арматуры на этот коэффициент. Значения <р следует принимать:

1. For floors and coverings made of prefabricated reinforced concrete flat slabs of solid and hollow-core, reinforced:

a) steel of class A-III, equal to 1.2;

b) steels of classes A-VI, At-VI, At-VII, B-1, Bp-I, equal to 0.9;

c) high-strength reinforcing wire of classes V-P, VR-P or reinforcing ropes of class K-7, equal to 0.8.

2. For. floors and coverings made of prefabricated reinforced concrete slabs with longitudinal bearing ribs "down" and box-section, as well as beams, girders and girders in accordance with the specified classes of reinforcement: a) (p = 1.1; b) q> => 0.95 ; c) cf = 0.9.

2.19. For structures made of any kind of concrete, the minimum requirements for structures made of heavy concrete with a fire resistance of 0.25 or 0.5 hours must be met.

2.20. The limits of fire resistance of load-bearing structures in table. 2, 4-8 and in the text are given for full standard loads with the ratio of the long-term part of the load G $ or to the full load Veer equal to 1. If this ratio is 0.3, then the fire resistance limit is doubled. For intermediate values G 8e r / V B er, the fire resistance limit is taken by linear interpolation.

2.21. The fire resistance limit of reinforced concrete structures depends on their static operating scheme. The fire resistance limit of statically indeterminate structures is greater than the fire resistance limit of statically determinate ones, if there is the necessary reinforcement at the points of action of negative moments. The increase in the fire resistance of statically undetermined bending reinforced concrete elements depends on the ratio of the cross-sectional areas of the reinforcement above the support and in the span according to table. one.

The ratio of the area of reinforcement above the support to the area of reinforcement in the span

Increase in the fire resistance of a bent statically indeterminate element,%. compared to the fire resistance of a statically determinate element

Note. For intermediate area ratios, the increase in the fire resistance limit is taken by interpolation.

The effect of the static uncertainty of structures on the fire resistance limit is taken into account if the following requirements are met:

a) at least 20% of the upper reinforcement required on the support must pass over the middle of the span;

b) the upper reinforcement above the extreme supports of the continuous system should be wound at a distance of at least 0.4 / in the direction of the span from the support and then gradually break off (/ is the span length);

c) all the upper reinforcement over the intermediate supports must continue to span by at least 0.15 / and then gradually break off.

Bending elements embedded on supports can be considered as continuous systems.

2.22. Table 2 shows the requirements for reinforced concrete columns made of heavy and lightweight concrete. These include requirements for the dimensions of columns exposed to fire from all directions, as well as those located in walls and heated from one side. In this case, dimension b refers only to columns, the heated surface of which is flush with the wall, or for a part of the column protruding from the wall and carrying the load. It is assumed that there are no holes in the wall near the column in the direction of the minimum dimension b.

For columns of solid circular cross-section, their diameter should be taken as dimension b.

Columns with the parameters given in table. 2, have an off-center applied load or a load with random eccentricity when reinforcing columns is not more than 3% of the concrete cross-section, with the exception of joints.

The fire resistance limit of reinforced concrete columns with additional reinforcement in the form of welded transverse grids installed with a step of not more than 250 mm should be taken according to table. 2, multiplying them by a factor of 1.5.

table 2

Concrete type	The width b of the bar and the distance to the bar of the reinforcement a	Minimum dimensions, mm, of reinforced concrete columns with fire resistance limits, h
Concrete type





(Y® “1.2 t / m 3)

2.23. The fire resistance limit of non-bearing concrete and reinforced concrete partitions and their minimum thickness / p are given in table. 3. The minimum thickness of the baffles ensures that the temperature on the unheated surface of the concrete element will not rise more than 160 ° C on average and will not exceed 220 ° C in a standard fire test. When determining t n, additional protective coatings and plasters should be taken into account in accordance with the instructions in paragraphs. 2.16 and 2.16.

Table 3

2.24. For load-bearing solid walls, the fire resistance limit, wall thickness t c and the distance to the axis of the reinforcement a are given in table. 4. These data are applicable to reinforced concrete central and eccentric

compressed walls, provided that the total force is located in the middle third of the width of the cross-section of the wall. In this case, the ratio of the height of the wall to its thickness should not exceed 20. For wall panels with platform support with a thickness of at least 14 cm, the fire resistance limits should be taken according to table. 4, multiplying them by a factor of 1.5.

Table 4

The fire resistance of ribbed wall slabs should be determined by the thickness of the slabs. The ribs should be connected to the slab with cable ties. The minimum dimensions of the ribs and the distance to the axes of the reinforcement in the ribs must meet the requirements for beams and are given in table. 6 and 7.

External walls made of two-layer panels, consisting of a boundary layer with a thickness of at least 24 cm of large-porous expanded clay-to-concrete of class B2-B2.5 (uv = 0.6-0.9 t / m 3) and a bearing layer with a thickness of at least 10 cm, with compression stresses in it no more than 5 MPa, have a fire resistance limit of 3.6 hours.

When using a combustible insulation in wall panels or ceilings, it is necessary to provide for the protection of this insulation around the perimeter with a non-combustible material during manufacture, installation or installation.

Walls of three-layer panels, consisting of two ribbed reinforced concrete slabs and insulation, of non-combustible or hard-to-combustible non-cotton or fiberboard slabs with a total cross-sectional thickness of 25 cm, have a fire resistance limit of at least 3 hours.

External curtain and self-supporting walls made of three-layer solid panels (GOST 17078-71 as amended), consisting of external (at least 50 mm thick) and internal reinforced concrete layers and an average of combustible insulation (foam grade PSB according to GOST 15588-70 as revised and others), have a fire resistance limit with a total cross-sectional thickness of 15-22 cm for at least 1 hour.

with an internal bearing layer of reinforced concrete M 200 with compressive stresses in it no more than 2.5 MPa and a thickness of 10 cm or M 300 with compressive stresses in it no more than 10 MPa and a thickness of 14 cm, the fire resistance limit is 2.5 hours.

The fire propagation limit for these structures is zero.

2.25. For stretched elements, the fire resistance limits, the width of the cross-section b and the distance to the axis of the reinforcement a are given in table. 5. These data refer to tensile elements of trusses and arches with non-stressed and pre-stressed reinforcement, heated from all sides. The total cross-sectional area of the concrete element must be at least 2b 2 Mi R, where b mip is the corresponding size for b, given in table. 5.

Table 5

Concrete type

] Minimum cross-sectional width b and distance to the reinforcement axis a

Minimum dimensions of reinforced concrete tension members, mm, with fire resistance limits, h

(y "= 1.2 t / m 3)

2.26. For statically definable freely supported beams heated from three sides, the fire resistance limits, the width of the beams b and the distances to the axis of the reinforcement a, flu. (Fig. 3) are given for heavy concrete in table. 6 and for the lung (y in = "1.2 t / m 3) in Table 7.

When heated on one side, the fire resistance limit of the beams is taken according to table. 8 as for slabs.

For beams with sloped sides, the width b shall be measured at the center of gravity of the tensile reinforcement (see Fig. 3).

When determining the fire resistance limit, the openings in the flanges of the beam may not be taken into account if the remaining cross-sectional area in the tensioned zone is not less than 2v 2,

To prevent concrete chipping in the ribs of the beams, the distance between the clamp and the surface should not be more than 0.2 of the rib width.

Minimum distance from

Rice. U Reinforcement of beams and

distance to the axis of the reinforcement of the element surface to the axis

any reinforcement bar must be at least required (Table 6) for a fire resistance of 0.5 h and at least half a.

Table b

Fire resistance limits. h	Mavällpyv raayers of reinforced concrete beams, mm	The minimum width of the edge b w. mm

With a fire resistance limit of 2 or more hours, freely supported I-beams with a distance between the centers of gravity of the shelves of more than 120 cm must have end thickenings equal to the beam width.

For I-beams, in which the ratio of the flange width to the wall width (see Fig. 3) b / b w is greater than 2, it is necessary to install transverse reinforcement in the rib. If the ratio b / b w is greater than 1.4, the distance to the axis of the reinforcement should be increased to 0.85aYb / bxa. For bjb v> 3, use table. 6 and 7 are not allowed.

In beams with large shear forces, which are perceived by the clamps installed near the outer surface of the element, the distance a (Tables 6 and 7) also applies to the clamps, provided they are located in zones where the calculated tensile stresses are greater than 0.1 of the compressive strength of concrete ... When determining the fire resistance limit of statically indeterminate beams, the instructions in clause 2.21 are taken into account.

Table 7

Fire resistance limits, h	Beam width b and distance to the reinforcement axis a	Minimum dimensions of reinforced concrete beams, mm	Minimum rib width "V mm

The fire resistance limit of beams made of armopolymer concrete based on furfurolacetone monomer with k = | 1b0 mm and a = 45 mm, a, = 25 mm, reinforced with steel of class A-III, is equal to 1 hour.

2.27. For freely supported slabs, the fire resistance limit, the thickness of the slabs /, the distance to the axis of the reinforcement a are given in table. eight.

The minimum slab thickness t ensures the heating requirement: the temperature on an unheated surface adjacent to the floor will, on average, increase by no more than 160 ° C and will not exceed 220 ° C. The backfill and floor made of non-combustible materials are combined into the overall thickness of the slab and increase its fire resistance. Combustible insulating elephants, laid on the cement preparation, do not reduce the fire resistance of the slabs and can be used. Additional layers of plaster can be attributed to the thickness of the slabs.

The effective thickness of a hollow-core slab for assessing the fire resistance limit is determined by dividing the cross-sectional area of the slab, minus the void areas, by its width.

When determining the limit of fire resistance of statically indeterminate plates, clause 2.21 is taken into account. In this case, the thickness of the plates and the distance to the axis of the reinforcement must correspond to those given in table. eight.

The limits of fire resistance of hollow-core ones, including those with voids.

located across the span, and ribbed with upward ribs panels and decks should be taken according to table. 8, multiplying them by a factor of 0.9.

The limits of fire resistance for heating two-layer slabs of light and heavy concrete and the required layer thickness are given in table. 9.

Table 8

Concrete type and slab characteristics		The minimum slab thickness t and the distance to the reinforcement axis a. mm	Fire resistance limits, c
Concrete type and slab characteristics
	Slab thickness
	Support on two sides or along a contour at 1y / 1x ^ 1.5
	Support along the contour / „// *< 1,5
	Slab thickness
	Support on both sides or along the contour with / „// * ^ 1.5
	Support along contour 1 at CH< 1,5

Table 9

If all the reinforcement is located at the same level, the distance to the axis of the reinforcement from the lateral surface of the slabs should be at least the thickness of the layer given in Tables b and 7.

2.28. In case of fire and fire tests of structures, concrete spalling can be observed in the case of its high humidity, which, as a rule, can be in structures immediately after their manufacture or when operating in rooms with high relative humidity. In this case, the calculation should be made according to the "Recommendations for the protection of concrete and reinforced concrete structures from brittle destruction in a fire" (M, Stroyizdat, 1979). If necessary, use the protective measures specified in this Recommendation or carry out routine tests.

2.29. During control tests, the fire resistance of reinforced concrete structures should be determined at concrete moisture content corresponding to its moisture content under operating conditions. If the concrete moisture content under operating conditions is unknown, then it is recommended to test the reinforced concrete structure after storage in a room with a relative air humidity of 60 ± 15% and a temperature of 20 ± 10 ° C for 1 year. To ensure the operational moisture content of concrete, before testing the structures, it is allowed to dry them at an air temperature not exceeding 60 ° C.

STONE CONSTRUCTIONS

2.30. The limits of fire resistance of stone structures are given in table. 10.

2.31. If in column b of the table. 10 indicates that the fire resistance limit of stone structures is determined by the II limit state, it should be considered that the I limit state of these structures does not occur earlier than II.

1 Walls and partitions made of solid and hollow ceramic and silicate bricks and stones in accordance with GOST 379-79. 7484-78, 530-80

Walls made of natural, lightweight concrete and gypsum stones, lightweight brickwork filled with lightweight concrete, non-combustible or hardly combustible heat-insulating materials

Table 10

MANUAL

FOR DETERMINING THE LIMITS OF FIRE RESISTANCE OF STRUCTURES,

STRUCTURAL FIRE SPREAD LIMITS

AND GROUPS OF FLAMMABILITY OF MATERIALS

(approved by order of TsNIISK of 19.12.1984 N 351 / l as amended in 2016)

Table 1

# G0 Ratio of the area of reinforcement above the support to the area of reinforcement in the span

Increase in the fire resistance limit of a bent statically indeterminate element,%, in comparison with the fire resistance limit of a statically determinate element

Note. For intermediate area ratios, the increase in the fire resistance limit is taken by interpolation.

The effect of the static uncertainty of structures on the fire resistance limit is taken into account if the following requirements are met:

A) at least 20% of the upper reinforcement required on the support must pass over the middle of the span;

B) the upper reinforcement above the extreme supports of the continuous system should be wound at a distance of at least 0.4 in the direction of the span from the support and then gradually break off (- span length);

C) all the upper reinforcement above the intermediate supports must continue to a span of at least 0.15 and then gradually break off.

Bending elements embedded on supports can be considered as continuous systems.

2.22. Table 2 shows the requirements for reinforced concrete columns made of heavy and lightweight concrete. These include requirements for the dimensions of columns exposed to fire from all directions, as well as those located in walls and heated from one side. In this case, the dimension refers only to columns, the heated surface of which is flush with the wall, or for the part of the column protruding from the wall and carrying the load. It is assumed that there are no holes in the wall near the column in the direction of the minimum dimension.

For columns of solid circular cross-section, their diameter should be taken as the size.

Columns with the parameters given in Table 2 have an eccentrically applied load or a load with random eccentricity when reinforcing the columns no more than 3% of the concrete cross-section, with the exception of joints.

table 2

Parties

2.23. The fire resistance limit of non-bearing concrete and reinforced concrete partitions is given in Table 3. The minimum thickness of the baffles ensures that the temperature on the unheated surface of the concrete element will on average rise by no more than 160 ° C and will not exceed 220 ° C in a standard fire test. When determining, additional protective coatings and plasters should be taken into account in accordance with the instructions in clauses 2.15 and 2.16.

Table 3

# G0 Concrete type Minimum partition thickness, mm, with fire resistance limits, h

0,25 0,5 0,75 1 1,5 2 2,5 3

Lightweight (= 1.2 t / m)

Cellular (= 0.8 t / m) -

2.24. For load-bearing solid walls, the fire resistance limit, wall thickness are given in Table 4. These data are applicable to reinforced concrete centrally and eccentrically compressed walls, provided that the total force is located in the middle third of the width of the cross-section of the wall. In this case, the ratio of the height of the wall to its thickness should not exceed 20. For wall panels with platform support at a thickness of at least 14 cm, the fire resistance limits should be taken according to Table 4, multiplying them by a factor of 1.5.

Table 4

# G0 Concrete type Thickness

And the distance

To the axis of the reinforcement Minimum dimensions of reinforced concrete walls, mm, with fire resistance limits, h

0,5 1 1,5 2 2,5 3

(= 1.2 t / m) 100

10 15 20 30 30 30

The fire resistance of ribbed wall slabs should be determined by the thickness of the slabs. The ribs should be connected to the slab with cable ties. The minimum dimensions of the ribs and the distances to the axes of the reinforcement in the ribs must meet the requirements for beams and are given in tables 6 and 7.

External walls of two-layer panels, consisting of a boundary layer with a thickness of at least 24 cm of large-porous expanded clay concrete of class B2-B2.5 (= 0.6-0.9 t / m) and a bearing layer with a thickness of at least 10 cm, with compressive stresses in it is not more than 5 MPa, have a fire resistance limit of 3.6 hours.

Walls of three-layer panels, consisting of two ribbed reinforced concrete slabs and insulation, of non-combustible or hard-to-combustible mineral wool or fiberboard slabs with a total cross-sectional thickness of 25 cm, have a fire resistance limit of at least 3 hours.

External curtain and self-supporting walls made of three-layer solid panels (GOST 17078-71 as amended), consisting of outer (at least 50 mm thick) and inner reinforced concrete layers and a middle one of combustible insulation (foam grade PSB according to # M12293 0 901700529 3271140448 1791701854 4294961312 4293091740 1523971229 247265662 4292033675 557313239 GOST 15588-70 # S with revision, etc.), have a fire resistance limit with a total cross-sectional thickness of 15-22 cm not less than 1 hour. For similar load-bearing walls with the connection of layers with metal bonds with a total thickness of 25 cm , with an internal bearing layer of reinforced concrete M 200 with compressive stresses in it no more than 2.5 MPa and a thickness of 10 cm or M 300 with compressive stresses in it no more than 10 MPa and a thickness of 14 cm, the fire resistance limit is 2.5 hours.

The fire propagation limit for these structures is zero.

2.25. For stretched members, the fire resistance limits, cross-sectional width and distance to the axis of the reinforcement are given in Table 5. These data refer to tensile elements of trusses and arches with tension-free and pre-stressed reinforcement, heated from all sides. The total cross-sectional area of the concrete element must be at least, where is the corresponding size for given in Table 5.

Table 5

# G0Concrete type

Minimum cross-sectional width and distance to the reinforcement axis Minimum dimensions of reinforced concrete tension members, mm, with fire resistance limits, h

0,5 1 1,5 2 2,5 3

25 40 55 65 80 90

25 35 45 55 65 70

2.26. For statically definable freely supported beams heated from three sides, the fire resistance limits are given for heavy concrete in Table 6 and for light concrete in Table 7.

Table 6

# G0 Limits of fire resistance, h

Minimum

Rib width, mm

40 35 30 25 1,5

65 55 50 45 2,5

90 80 75 70 Table 7

# G0 Limits of fire resistance, h

Beam width and distance to the reinforcement axis Minimum dimensions of reinforced concrete beams, mm

Minimum rib width, mm

40 30 25 20 1,5

55 40 35 30 2,0

65 50 40 35 2,5

90 75 65 55 2.27. For freely supported slabs, the fire resistance limit is in table 8.

Table 8

# G0 Concrete type and slab characteristics

Minimum plate thickness and distance to the reinforcement axis, mm Fire resistance limits, h

0,2 0,5 1 1,5 2 2,5 3

Plate thickness 30 50 80 100 120 140 155

Support on both sides or along the contour at 1.5

Support along the contour 1.5 10

(1.2 t / m) Slab thickness 30 40 60 75 90 105 120

Support on both sides or along the contour at 1.5 10

Support along the contour 1.5 10

The fire resistance limits of hollow-core, including those with voids located across the span, and ribbed panels and decks with upward ribs should be taken according to Table 8, multiplying them by a factor of 0.9.

The fire resistance limits for heating two-layer slabs of light and heavy concrete and the required layer thickness are given in Table 9.

Table 9

# G0 Concrete location on the fire side

Minimum layer thicknesses

Out of the lung and

Heavy concrete, mm Fire resistance limits, h

0,5 1 1,5 2 2,5 3

25 35 45 55 55 55

20 20 30 30 30 30

If all reinforcement is located at the same level, the distance to the axis of the reinforcement from the lateral surface of the slabs should be at least the layer thickness given in Tables 6 and 7.

STONE CONSTRUCTIONS

2.30. The limits of fire resistance of stone structures are given in Table 10.

Table 10

# G0N p.p. Brief description of the structure Diagram (section) of the structure Dimensions, cm Fire resistance limit, h Fire resistance limit state (see clause 2.4)

1 and partition walls of solid and hollow ceramic and silicate bricks and stones on # M12293 0 871001065 3271140448 181493679 247265662 4292033671 3918392535 2960271974 827738759 4294967268GOST S # 379-79, # M12293 1 3271140448 901700265 1662572518 247265662 4292033671 557313239 2960271974 3594606034 42930879867484-78 # S, # M12293 2 871001064 3271140448 1419878215 247265662 4292033671 3918392535 2960271974 827738759 4294967268530-80 # S 6.5 0.75 II

2 Walls made of natural, lightweight concrete and gypsum stones, lightweight brickwork filled with lightweight concrete, fireproof or non-combustible heat-insulating materials 6 0.5 II

3 Walls made of vibro-brick reinforced panels made of silicate and ordinary clay bricks with solid support on the mortar and at medium stresses with the main combination of only vertical standard loads:

A) 30 kgf / cm

B) 31-40 kgf / cm

B)> 40 kgf / cm

(based on test results)

Half-timbered walls and partitions made of bricks, concrete and natural stones with a steel frame:

A) unprotected

See table 11

B) placed in the thickness of the wall with unprotected walls or shelves of frame elements

B) protected by plaster on a steel wall

D) clad with brick with a cladding thickness

Partitions made of hollow ceramic stones with a thickness determined minus voids 3.5 0.5

Brick columns and pillars with a section = 25x25

LOADING METAL STRUCTURES

2.32. fire resistance limits of load-bearing metal structures are given in Table 11.

Table 11

# G0N p.p. Brief characteristic of structures Structure diagram (section) Dimensions, cm Fire resistance limit, h Fire resistance limit state (see clause 2.4)

Steel beams, girders, girders and statically definable trusses, with the support of slabs and floorings along the upper chord, as well as columns and posts without fire protection with the reduced metal thickness indicated in column 4 = 0.3 0.12

Steel beams, girders, girders and statically definable trusses when the slabs and decks are supported on the lower chords and shelves of the structure with the metal thickness of the lower chord specified in column 4 0.5

Steel beams of floors and staircase structures for fire protection on a mesh with a layer of concrete or plaster 1

4 Steel structures with fire protection made of heat-insulating plaster filled with perlite sand, vermiculite and granulated wool with a plaster thickness specified in column 4 and with a minimum thickness of the section element, mm

4,5-6,5 2,5 0,75

10,1-15 1,5 0,75

20,1-30 0,8 0,75

5 Steel posts and columns with fire protection

A) from plaster on a grid or from concrete slabs 2.5 0.75 IV

2.5 b) from solid ceramic and silicate bricks and stones 6.5

B) from hollow ceramic and silicate bricks and stones

D) from gypsum boards

D) from expanded clay slabs

Steel structures with fire protection:

A) intumescent coating VPM-2 (# M12291 1200000327 GOST 25131-82 # S) at a flow rate of 6 kg / m and with a coating thickness after drying of at least 4 mm

B) fire-retardant phosphate coating on steel (according to # M12291 1200000084 GOST 23791-79 # S) 1

Membrane-type coating:

A) from steel grade St3kp with a sheet thickness of 1.2 mm

B) from aluminum alloy AMG-2P with a membrane thickness of 1 mm;

The same, with a fire retardant intumescent coating * VPM-2 with a flow rate of 6 kg / m. 0.6

2.35. The fire resistance limit of unprotected steel fasteners, installed for design reasons without calculation, should be taken equal to 0.5 h.

BEARING WOODEN STRUCTURES.

2.36. The fire resistance limits of load-bearing timber structures are shown in Table 12.

Table 12

# G0N p.p. Brief description of the structure Diagram (section) of the structure Dimensions, cm Fire resistance limit, h Fire resistance limit state (see clause 2.4)

1 Wooden walls and partitions, plastered on both sides, with a plaster layer thickness of 2 cm 10 0.6 I, II

2 Wooden frame walls and partitions, plastered or sheathed on both sides with sheet fire-resistant or non-combustible materials with a thickness of at least 8 mm, with filling of voids:

A) combustible materials 0.5 I, II

B) fireproof materials

0.75 3 Wooden floors with a roll or filing and plaster on shingles or on a grid with a plaster thickness of 2 cm

Overlapping on wooden beams when rolling from non-combustible materials and protection with a layer of gypsum or plaster thick

Glued wooden beams of rectangular cross-section for covering industrial buildings. Series 1.462-2, issue 1, 2

Glued wooden beams, gable and single-pitch cantilever. Series 1.462-6

Glued wooden beams with corrugated plywood wall

Regardless of size

Glued wooden frames made of straight elements and bent glued frames

Glued columns of rectangular cross-section, loaded with eccentricity, with a load of 28 tons

Glued and solid wood columns and columns, protected with plaster 20

COVERINGS AND COVERINGS WITH SUSPENDED CEILINGS.

2.41. (2.2 Table 1, note 1). The limits of fire resistance of coatings and ceilings with suspended ceilings are established as for a single structure.

2.42. The limits of fire resistance of coatings and floors with steel and reinforced concrete load-bearing structures and with suspended ceilings, as well as the limits of fire propagation along them, are given in Table 13.

Table 13

Construction diagram

Dimensions, cm

Fire resistance limit - bone, h

Limit of distribution of fire, see Limit state for fire resistance (see clause 2.4.)

Steel or reinforced concrete of heavy concrete load-bearing structures of coatings and floors (beams, girders, girders and statically determinate trusses) when supported by slabs and floorings made of non-combustible materials along the upper chord, with suspended ceilings with a minimum ceiling filling thickness B specified in column 4, with frame made of thin-walled metal profiles:

A) filling - decorative gypsum boards reinforced with fiberglass; frame - steel, hidden

B) filling - gypsum decorative boards reinforced with fiberglass, frame - steel, hidden

B) filling - gypsum decorative boards, fiberglass-reinforced, perforated, perforated area 4.6%; frame - steel, hidden

D) filling - gypsum-perlite decorative plates, reinforced with fiberglass; frame - steel, open, filled with gypsum bars inside

E) filling - decorative gypsum boards, not reinforced, perforated, perforated area 2.4%; frame - steel, open

E) filling - perforated gypsum decorative boards reinforced with asbestos waste; frame - steel, open, filled inside with mineral wool

G) filling - cast gypsum sound-absorbing plates filled with mineral wool; frame - steel, open

I) filling - cast gypsum sound-absorbing slabs filled with gypsum threshold; frame - steel, open

K) filling - cast gypsum sound-absorbing slabs filled with gypsum threshold; frame - steel, open, filled inside with mineral wool

0.8 + 2.2 1.5 0 IV

L) filling - hard mineral wool slabs of the Akmigran type with steel dowels for sealing the seams; frame - steel, hidden

M) filling - hard mineral wool slabs of the Akmigran type with steel dowels for sealing the seams; frame - steel, open

H) filling - hard mineral wool slabs of the Akmigran type with steel dowels for sealing the seams; frame - hidden aluminum

P) filling - hard mineral wool slabs of the Akmigran type without dowels for sealing the seams; frame - hidden aluminum

P) filling - rigid vermiculite plates; frame - steel, open, filled inside with mineral wool

C) filling - stamped steel panels filled with semi-rigid mineral wool slabs on a synthetic binder; frame - steel, hidden

T) filling - semi-rigid mineral wool slabs on a synthetic binder, laid on a steel mesh with cells up to 100 mm

U) two-layer filling, the upper layer - semi-rigid mineral wool slabs on a synthetic binder, laid on a steel mesh with cells up to 100 mm, the lower layer - fiberglass plates laid on a decorative aluminum sheet

F) filling - asbestos-cement-perlite slabs; frame - steel, open

X) filling - plasterboard sheets according to # M12293 0 1200003005 3271140448 2609519369 247265662 4292033676 3918392535 2960271974 915120455 970032995 GOST 6266-81 # S with rev.; frame - steel, open

C) filling - aluminum sheets coated with VPM-2; frame - steel, hidden

W) filling - steel sheets without a fire retardant coating; frame - steel, open

Ribbed reinforced concrete slabs or roofs with suspended ceilings, prestressed from heavy concrete, with a minimum ceiling filling thickness specified in column 4, with an open frame of thin-walled steel profiles:

A) filling - asbestos-cement-perlite slabs

B) filling - rigid vermiculite plates

GUARDING STRUCTURES USING METAL, WOOD,

ASBESTOS CEMENT, PLASTICS AND OTHER EFFECTIVE MATERIALS.

2.43. The limits of fire resistance and fire propagation along enclosing structures using metal, wood, asbestos cement, plastics and other effective materials are given in Table 14, the data given in Table 12 for walls and partitions made of wood should also be taken into account.

2.44. When establishing the fire resistance limits of external walls made of hinged panels, it should be borne in mind that their fire resistance limit state can occur not only due to the onset of the fire resistance limit state of the panels themselves, but also the loss of the bearing capacity of the structures to which the panels are attached - girders, half-timbered elements, floors. Therefore, the fire resistance limit of external walls made of curtain panels with metal sheathing, which, as a rule, are used in combination with a metal frame without fire protection, is taken equal to 0.25 h, except for those cases when the panels collapse earlier (see paragraphs 1- 5, Table 14).

If curtain wall panels are attached to other structures, including metal structures with fire protection, and the attachment points are protected from the effects of fire, then the fire resistance limit of such walls should be established experimentally. When establishing the fire resistance limit of walls made of hinged panels, it is allowed to assume that the destruction of steel fastening elements unprotected from fire, the dimensions of which are taken on the basis of the strength calculation results, occurs in 0.25 h, and fastening elements, the dimensions of which are taken for design reasons (without calculation), occurs after 0.5 hours.

Table 14

Brief description of the design

Construction diagram (section)

Dimensions, cm

Fire resistance limit - bone, h

Fire spreading limit, cm

Limiting state for fire resistance (see clause 2.4.)

Exterior walls

1 Exterior walls of curtain wall panels with metal cladding:

A) from three-layer frameless panels with steel profiled sheathing in combination with combustible foam insulation (see clause 2.44)

B) the same, in combination with fireproof foam insulation

B) the same, from three-layer frameless panels with aluminum profiled sheathing in combination with combustible foam insulation

D) the same, in combination with fireproof foam insulation

2 External walls made of hinged three-layer panels with external sheathing made of profiled steel sheet, internal - of fibreboards with insulation made of phenol-formaldehyde foam FRP-1, regardless of the bulk density of the latter

3 Exterior walls made of hinged three-layer panels with outer sheathing of profiled steel sheet with inner sheathing of asbestos-cement sheets and insulation made of polyurethane foam of the PPU-317 formulation

4 External metal walls of buildings of layer-by-layer assembly with insulation made of glass and mineral wool plates, including increased rigidity, and internal cladding made of non-combustible materials

External metal walls made of hinged two-layer panels with internal cladding made of non-combustible and non-combustible materials and insulation made of non-combustible foams

Exterior walls made of suspended asbestos-cement extrusion panels, hollow and filled with mineral wool slabs

External walls made of hinged three-layer frame panels with cladding of 10 mm thick asbestos-cement sheets *:

A) with a frame made of asbestos-cement profiles and a heater made of non-combustible or non-combustible mineral wool slabs when the skin is fastened to the frame with steel screws

B) the same, with insulation made of polystyrene foam PSVS

B) with a wooden frame and with insulation made of non-combustible or hardly combustible materials

D) with a metal frame without insulation

D) by # M12291 1200000366 GOST 18128-82 # S

External walls made of hinged panels with an outer sheathing of polyester fiberglass PN-1C or PN-67, with an inner sheathing of two gypsum plasterboard sheets according to # M12293 0 1200003005 3271140448 2609519369 247265662 4292033676 3918392535 292051974 91566M and with insulation made of phenol-formaldehyde foam brand FRP-1 (when the panels are located in reinforced concrete and brick loggias)

External walls made of hinged three-layer panels with asbestos-cement sheathing and insulation made of pressed rice straw slabs (riplit)

External and internal walls made of wood concrete grade M-25, with a bulk density of 650 kg / m, plastered with cement-sand walls on both sides with cement-sand sides *

_______________

* The text corresponds to the original. - Note "CODE".

Partitions

Fiberboard or gypsum slag partitions with a wooden frame, plastered on both sides with cement-sand mortar with a layer thickness of at least 1.5 cm

Gypsum and gypsum fiber partitions with the content of organic substances evenly distributed over the volume of structures up to 8% by weight 5

Partitions made of hollow glass blocks, glass profiles, including when filling voids with mineral wool slabs

Partitions made of asbestos-cement extrusion panels, with grouting of joints with cement-sand mortar

A) void

B) when filling voids with insulation made of hardly combustible or non-combustible materials<12

Partitions made of three-layer panels on a wooden frame, cladding on both sides with asbestos-cement sheets and with a middle layer of mineral wool boards 8

Three-layer partitions made of gypsum plasterboard sheets according to # M12293 0 1200003005 3271140448 2609519369 247265662 4292033676 3918392535 2960271974 915120455 970032995 GOST 6266-81 # S with rev. 10 mm thick

A) on a wooden frame with mineral wool insulation

B) the same, void

B) on a metal frame with mineral wool insulation

D) the same, void

Partitions made of plasterboard sheets according to # M12293 0 1200003005 3271140448 2609519369 247265662 4292033676 3918392535 2960271974 915120455 970032995 GOST 6266-81 # S with rev. 14 mm thick, hollow:

A) on a metal frame

B) on a wooden frame

The same, with the middle layer of mineral wool boards:

A) on a metal frame

B) on an asbestos-cement frame

B) on a wooden frame

Hollow partitions with plasterboard sheathing on both sides according to # M12293 0 1200003005 3271140448 2609519369 247265662 4292033676 3918392535 2960271974 915120455 970032995 GOST 6266-81 # S with change, 14 mm thick in two layers:

A) on a metal frame

B) on an asbestos-cement frame

B) on a wooden frame

Partitions made of three-layer panels with gypsum-cement sheathing on both sides with a thickness of 15 mm and a middle layer of mineral wool slabs with a transverse arrangement of fibers

Partitions made of three-layer panels with cladding made of aluminum sheets and a middle layer of perlitoplastic concrete with a bulk density of 150 kg / m

Partitions made of three-layer panels with cladding on both sides of cement-bonded particle boards (DSP) 10 mm thick

A) hollow with a frame made of metal or asbestos-cement profiles

B) hollow on a wooden frame

B) with a mineral wool insulation with a frame made of metal or asbestos-cement profiles

D) with insulation made of mineral wool boards on a wooden frame

Partitions made of three-layer panels with cladding of 1 mm steel sheets and a middle layer of honeycomb plates

Partitions made of gypsum concrete panels on a wooden frame with grouting of joints with cement-sand mortar

Coverings and slabs

Coverings made of three-layer panels with cladding made of galvanized steel profiled sheets with a thickness of 0.8-1 mm:

Two-layer panel coverings with outer sheathing of profiled steel sheet:

A) with PSF-VNIIST foam insulation and fiberglass bottom facing, painted with VA-27 water-based paint 0.5 mm thick

B) with insulation made of foam plastic FRP-1, filled with glass fiber and cladding from the bottom of fiberglass

Coverings of two-layer panels with an internal bearing steel profiled sheet, with gravel backfill 20 mm thick over a waterproofing carpet:

A) with insulation made of combustible foam

B) with a heater made of non-combustible polystyrene

Coverings based on steel profiled sheet with roll roofing and gravel backfill 20 mm thick and with

Thermal insulation:

A) from plate combustible foam

B) from mineral wool slabs of increased rigidity and slabs from perlitoplast concrete

B) from perlitophosphogel and calibrated aerated concrete slabs

Coverings from frame slabs, including truss type, with skinned from flat and corrugated asbestos-cement sheets:

A) insulation made of mineral wool slabs and a frame made of asbestos-cement channels or metal

0,25

0

I

b) with insulation made of phenol-formaldehyde foam grade FRP-1 and a frame made of wood, asbestos-cement channels or metal

14

0,25

<25

I

30

Coverings from extruded asbestos-cement panels 120 mm thick with filling of voids with mineral wool boards 12

0,25

0

I

18

0,5

0

I

31

Coverings from three-layer frame panels with a wooden frame of massive section, fireproof roof, with a bottom filing of asbestos-cement-perlite sheets and insulation made of glass wool or mineral wool slabs

23

0,75

<25

I

32

Coverings made of glued wood frame panels with a span of up to 6 m with plywood sheathing with a thickness of 12 and 8 mm, a frame made of glued timber and a mineral wool insulation

22

0,25

>25

I

33

Frameless board coverings with plywood or chipboard sheathing with foam insulation

12

<0,25

>25

I

34

Coverings made of plates of the AKD type without insulation, with a wooden frame and with a bottom sheathing of asbestos cement

14

0,5

<25

I

35

Coverings and ceilings made of slabs with a span of 6 m with ribs made of glued timber with a section of 140x360 mm and a flooring of boards 50 mm thick

11

0,75

>25

I

36

Ceilings made of wood concrete panels with a concrete substrate in the tensioned zone with a protective layer of working reinforcement of 10 mm

18

1

0

I

Doors

37

Fireproof steel doors filled with fireproof mineral wool plates 5 thick

1

II, III

8

1,3

II, III

9,5

1,5

II, III

38

Doors with steel hollow (with air spaces) panels

-

0,5

III

39

Doors with wooden panels with a thickness, sheathed over asbestos cardboard with a thickness of at least 5 mm with overlapping roofing steel 3

1

II, III

4

1,3

II, III

5

1,5

II, III

40

Doors with a thickness of panels made of blockboard, deeply impregnated with fire retardants 4

0,6

II, III

6

1

II, III

Window

41

Filling openings with hollow glass blocks when laying them on cement mortar and reinforcing horizontal joints with a block thickness of 6

1,5

-

III

10

2

-

III

42

Filling openings with single steel or reinforced concrete bindings with reinforced glass when fastening glass with steel cotter pins, clamps or wedge clamps

0,75 -

III

43

The same, with double bindings

1,2

-

III

44

Filling openings with single steel or reinforced concrete sashes with reinforced glass when glass is fastened with steel corners

0,9

-

III

45

Filling openings with single steel or reinforced concrete bindings with tempered glass when fastening glass with steel cotter pins or clamps 0.25

-

III

3. BUILDING MATERIALS. FLAMMABILITY GROUPS.

3.2. Table 15 shows the flammability groups of various types of building materials.

3.3. Fireproof, as a rule, includes all natural and artificial inorganic materials, as well as metals used in construction.

Table 15

# G0N p.p. Material name

Code of technical documentation for material Flammability group

1

Plywood, glued

GOST 3916-69

Combustible

bakelized

# M12291 1200008199 GOST 11539-83 # S

"

birch

GOST 5.1494-72 with rev.

"

decorative

# M12291 1200008198 GOST 14614-79 # S

"

2

Chipboards

# M12293 0 1200005273 3271140448 1968395137 247265662 4292428371 557313239 2960271974 3594606034 4293087986 GOST 10632-77 # S with rev.

Combustible

3

Fiber boards

# M12293 0 9054234 3271140448 3442250158 4294961312 4293091740 3111988763 247265662 4292033675 557313239 GOST 4598-74 # S with rev.

"

4

Wood-mineral boards

TU 66-16-26-83

Hardly combustible

5

Decorative laminated paper plastic

# M12291 901710663 GOST 9590-76 # S with rev.

Combustible

6

Plasterboard sheets

# M12293 0 1200003005 3271140448 2609519369 247265662 4292033676 3918392535 2960271974 915120455 970032995 GOST 6266-81 # S with rev.

Hardly combustible

7

Gypsum fiber sheets

TU 21-34-8-82

"

8

Cement particle boards

TU 66-164-83

"

9

Organic structural glass

GOST 15809-70E with rev.

Combustible

technical

# M12293 0 1200020683 0 0 0 0 0 0 0 0 GOST 17622-72Е # S with rev.

"

10

Structural fiberglass

# M12291 1200020655 GOST 10292-74 # S with rev.

Hard to burn

11

Fiberglass polyester sheet

MRTU 6-11-134-79

Combustible

12

Roll fiberglass on perchlorovinyl varnish

TU 6-11-416-76

Hard to burn

13

Polyethylene film

# M12291 1200006604 GOST 10354-82 # S

Combustible

14

Polystyrene film

# M12291 1200020667 GOST 12998-73 # S with rev.

"

15

Roofing glassine

# M12291 9056512 GOST 2697-75 # S

Combustible

16

Roofing material

# M12291 871001083 GOST 10923-82 # S

"

17

Rubber gaskets

# M12291 901710453 GOST 19177-81 # S

"

18

Folgoizol

# M12291 901710670 GOST 20429-75 # S with rev.

"

19

Enamel HP-799 on chlorosulfonated polyethylene

TU 84-618-75

Fireproof

20

Bitumen-polymer mastic BPM-1

TU 6-10-882-78

"

21

Divinyl Styrene Sealant

TU 38405-139-76

Combustible

22

Epoxy-coal mastic

TU 21-27-42-77

Combustible

23

Glass pore

TU 21-RSFSR-2.22-74

Incombustible

24

Perlitophosphogel thermal insulation plates

GOST 21500-76

Fireproof

25

Thermal insulation boards and mats made of mineral wool on a synthetic binder, grades 50-125

# M12291 1200000313 GOST 9573-82 # S

Hardly combustible

26

Mineral wool stitched mats

# M12291 1200000732 GOST 21880-76 # S

"

27

Thermal insulation boards made of polystyrene foam

# M12293 0 901700529 3271140448 1791701854 4294961312 4293091740 1523971229 247265662 4292033675 557313239 GOST 15588-70 # S rev.

Combustible

28

Thermal insulation boards made of polystyrene based on resole phenol-formaldehyde resins. Foam plastic FRP-1 with density, kg / m:

# M12291 901705030 GOST 20916-75 # S

80 and more

Hard to burn

less than 80

Combustible

29

Polyurethane foams:

PPU-316

TU 6-05-221-359-75

"

PPU-317

TU 6-05-221-368-75

"

30

PVC foam grade

PV-1

TU 6-06-1158-77

Combustible

PVC-1

TU 6-05-1179-75

"

31

Polyurethane foam sealing gaskets GOST 10174-72

Combustible

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TsNIISK them. Kucherenko of the USSR State Construction Committee

Manual

Moscow 1985

ORDER OF LABOR RED BANNER CENTRAL RESEARCH INSTITUTE OF BUILDING CONSTRUCTIONS them. V. A. KUCHERENKO SHNIISK them. Kucherenko) GOSSTROYA USSR

Manual

FOR DETERMINING THE LIMITS OF FIRE RESISTANCE OF STRUCTURES,

LIMITS

DISTRIBUTION

fire on structures

FLAMMABILITY OF MATERIALS (TO SNiP P-2-80)

Approved by

1®SH

MOSCOW STROYIZDAT 1985

when heated. The degree of resistance reduction is greater for hardened high-strength rebar steel than for low-carbon steel bar rebar.

2.18. Tab. 5-8 are compiled for reinforced concrete elements with non-prestressed and prestressed reinforcement on the assumption that the critical heating temperature of the reinforcement is 500 ° C. This corresponds to reinforcing steels of classes A-I, A-II, A-1v, A-Shv, A-IV, At-IV, A-V, At-V. The difference in critical temperatures for other classes of reinforcement should be taken into account by multiplying those given in table. 5-8 fire resistance limits by the coefficient f, or dividing those given in table. 5-8 distances to the axes of the reinforcement by this factor. The values of φ should be taken:

1. For floors and coverings made of prefabricated reinforced concrete flat slabs of solid and hollow-core, reinforced:

a) steel of class A-III, equal to 1.2;

b) steels of classes A-VI, At-VI, At-VII, B-1, Bp-I, equal to 0.9;

c) high-strength reinforcing wire of classes В-П, Вр-Н or reinforcing ropes of class К-7, equal to 0.8.

2.19. For structures made of any kind of concrete, the minimum requirements for structures made of heavy concrete with a fire resistance of 0.25 or 0.5 hours must be met.

2.20. The limits of fire resistance of load-bearing structures in table. 2, 4-8 and in the text are given for full standard loads with the ratio of the long-term part of the load G eor to the full load Veer equal to 1. If this ratio is 0.3, then the fire resistance limit is doubled. For intermediate values G S er / Vser, the fire resistance limit is taken by linear interpolation.

Note. For intermediate area ratios, the increase in the fire resistance limit is taken by interpolation.

The effect of the static uncertainty of structures on the fire resistance limit is taken into account if the following requirements are met:

a) at least 20% of the upper reinforcement required on the support must pass over the middle of the span;

c) all the upper reinforcement over the intermediate supports must continue to span by at least 0.15 / and then gradually break off.

Bending elements embedded on supports can be considered as continuous systems.

For columns of solid circular cross-section, their diameter should be taken as dimension b.

table 2

Concrete type	Column width I b and distance TO OCF reinforcement a	Minimum dimensions, mm, of reinforced concrete columns with fire resistance limits, h
Concrete type	Column width I b and distance TO OCF reinforcement a





(Yb = 1.2 t / m 3)

2.23. The fire resistance limit of non-bearing concrete and reinforced concrete partitions and their minimum thickness t u are given in table. 3. The minimum thickness of the baffles ensures that the temperature on the unheated surface of the concrete element will not rise more than 160 ° C on average and will not exceed 220 ° C in a standard fire test. When determining t n, additional protective coatings and plasters should be taken into account in accordance with the instructions in paragraphs. 2.16 and 2.16.

Table 3

	Minimum fire resistance partition thickness, h	with limits
Concrete type

[y u = 1.2 t / m 3)
Cellular KYb = 0.8 t / m 3)

compressed walls, provided that the total force is located in the middle third of the width of the cross-section of the wall. In this case, the ratio of the height of the wall to its thickness should not exceed 20. For wall panels with a -platform support with a thickness of at least 14 cm, the fire resistance limits should be taken according to table. 4, multiplying them by a factor of 1.5.

Table 4

Concrete type	Thickness t c and distance to the axis of the reinforcement a	Minimum dimensions of reinforced concrete walls, mm, with fire resistance limits, h
Concrete type



<Ув = 1,2 т/м 3)

The fire resistance of ribbed wall slabs should be determined by

the thickness of the slabs. The ribs should be connected to the slab with cable ties. The minimum dimensions of the ribs and the distance to the axes of the reinforcement in the ribs must meet the requirements for beams and are given in table. 6 and 7.

External walls of two-layer panels, consisting of a boundary layer with a thickness of at least 24 cm of large-porous expanded clay-to-concrete of class B2-B2.5 (in v - 0.6-0.9 t / m 3) and a bearing layer with a thickness of at least 10 cm , with compressive stresses in it no more than 5 MPa, have a fire resistance limit of 3.6 hours.

External curtain and self-supporting walls made of three-layer solid panels (GOST 17078-71 as amended), consisting of external (at least 50 mm thick) and internal reinforced concrete layers and an average of combustible insulation (foam grade PSB according to GOST 15588 - 70 as rev. and others), have a fire resistance limit with a total cross-sectional thickness of 15-22 cm for at least 1 hour.

with an internal load-bearing layer of reinforced concrete M 200 with compressive stresses in it no more than 2.5 MPa and a thickness of 10 cm or M 300 with compressive stresses in it no more than 10 MPa and a thickness of 14 cm, the fire resistance limit is 2.5 hours.

The fire propagation limit for these structures is zero.

2.25. For stretched elements, the fire resistance limits, the width of the cross-section b and the distance to the axis of the reinforcement a are given in table. 5. These data refer to tensile elements of trusses and arches with tension-free and pre-tensioned reinforcement, heated from all sides. The total cross-sectional area of the concrete element must be at least 25 2 min, where b mean is the corresponding size for 6, given in table. 5.

Table 5

Concrete type	The minimum width of the cross-section b and the distance to the axis of the reinforcement a	Minimum dimensions of reinforced concrete stretched elements, mm, with fire resistance limits, h
Concrete type



(Yb = * 1.2 t / m 3)

2.26. For statically definable freely supported beams heated from three sides, the fire resistance limits, the width of the beams b and

distances to the axis of reinforcement a, a yu (Fig. 3) are given for heavy concrete in table. 6 and for the lung (yv = (1.2 t / m 3) in Table 7.

When heated on one side, the fire resistance limit of the beams is taken according to table. 8 as for slabs.

For beams with sloped sides, the width b shall be measured at the center of gravity of the tensile reinforcement (see Fig. 3).

When determining the fire resistance limit, the openings in the flanges of the beam may not be taken into account if the remaining cross-sectional area in the tensioned zone is not less than 2v 2,

To prevent chipping of concrete in the ribs of the beams, the distance between the clamp and the surface should not be more than 0.2 rib width.

Minimum distance a! from the surface of the element to the axis

/ £ 36 ")

Rice. 3. Reinforcement ball and distance to the axis of the reinforcement

any reinforcement bar must be at least required (Table 6) for a fire resistance of 0.5 h and at least half a.

Table b

Fire resistance limits, h	Beam width b and distance to the reinforcement axis a	Mkhyamalny dimensions of reinforced concrete beams, mm	Minimum rib width b w. mm

For I-beams, in which the ratio of the flange width to the wall width (see Fig. 3) bjb w is greater than 2, it is necessary to install transverse reinforcement in the rib. If the ratio b / b w is greater than 1.4, the distance to the axis of the reinforcement should be increased to

0, S5ayb / b w. For bjb w> 3, use table. 6 and 7 are not allowed.

Table 7

Fire resistance limits, h	Beam width b and distance to the reinforcement axis a	Minimum dimensions of reinforced concrete beams, mm	Minimum rib width b w, mm

The fire resistance limit of beams made of armopolymer concrete based on furfurolacetone monomer with 5 = C60 mm and a-45 mm, a w = 25 mm, reinforced with steel of class A-III, is equal to 1 hour.

2.27. For freely supported slabs, the fire resistance limit, the thickness of the slabs t, the distance to the axis of the reinforcement a are given in table. eight.

The minimum slab thickness t ensures the heating requirement: the temperature on an unheated surface adjacent to the floor will, on average, increase by no more than 160 ° C and will not exceed 220 ° C. The backfill and floor made of non-combustible materials are combined into the overall thickness of the slab and increase its fire resistance. Combustible insulating layers placed on the cement preparation do not reduce the fire resistance of the slabs and can be used. Additional layers of plaster can be attributed to the thickness of the slabs.

The effective thickness of a hollow-core slab for assessing the fire resistance limit is determined by dividing the cross-sectional area or< ты, за вычетом площадей пустот, на ее ширину.

Limits of fire resistance of hollow-core ones, including those with voids *

located across the span, and ribbed with upward ribs panels and decks should be taken according to table. 8, multiplying them by a factor of 0.9.

The location of concrete from the side of the fire impact	Minimum layer thicknesses 11 from light and 1 2 from heavy concrete, mm	Fire resistance limits, h
The location of concrete from the side of the fire impact



(Yb = 1.2 t / m 3)

The limits of fire resistance for heating two-layer slabs of light and heavy concrete and the required layer thickness are given in table. 9.

Table 8

Concrete type and characteristics		The minimum slab thickness t and distance	Fire resistance limits, c
stick plate		position to the axis of the reinforcement a, mm
	Slab thickness

	Contour support lyjlx< 1,5
	Slab thickness
(Yb = 1.2 t / m 3)	Support on two sides or along a contour when
	Support along the contour 1u / 1х< 1,5
				Table 9

If all the reinforcement is located at the same level, the distance to the axis of the reinforcement from the lateral surface of the slabs should be at least the layer thickness given in table. 6 and 7.

STONE CONSTRUCTIONS

2.30. The limits of fire resistance of stone structures are given in table. 10.

2.31. If in column 6 of the table. 10 indicates that the fire resistance limit of stone structures is determined by the II limit state, it should be considered that the I limit state of these structures does not occur earlier than II.

Table 10

Diagram (section) of the structure

Dimensions a, cm	Fire resistance limit, h	Limiting state for fire resistance (see clause 2.4)

Scientific Council of TsNIISK named after Kucherenko State Construction Committee of the USSR.

A guide for determining the limits of fire resistance of structures, the limits of fire propagation along structures and groups of flammability of materials (to SNiP P-2-80) / TsNIISK im. Kucherenko.- M .: Stroyizdat, 1985.-56 p.

Developed for SNiP P-2-80 "Fire safety standards for the design of buildings and structures." Provides reference data on the limits of fire resistance and fire propagation on building structures made of reinforced concrete, metal, wood, asbestos cement, plastics and other building materials, as well as data on the flammability groups of building materials.

For engineering and technical workers of design, construction organizations and bodies of state fire supervision.

Tab. 15, fig. 3.

and -Instructions-norm. II issue - 62-84

Continuation of table. 10

3.7 2.5 (based on test results)

FOREWORD

This Manual was developed for SNiP II-2-80 "Fire safety standards for the design of buildings and structures." It contains data on the standardized indicators of fire resistance and fire hazard of building structures and materials.

Sec. 1 of the manual was developed by TsNIISK them. Kucherenko (Doctor of Technical Sciences, Prof. I. G. Romanenkov, Candidate of Technical Sciences V. N. Siegern-Korn). Sec. 2 developed by TsNIISK them. Kucherenko (Doctor of Technical Sciences

I. G. Romanenkov, technical candidates Sci. V. N. Siegern-Korn,

L. N. Bruskova, G. M. Kirpichenkov, V. A. Orlov, V. V. Sorokin, engineers A. V. Pestritsky, | I. Yashin)); NIIZhB (Doctor of Technical Sciences

V. V. Zhukov; Dr. Tech. Sciences, prof. A. F. Milovanov; Cand. phys.-mat. Sciences AE Segalov, Candidates of Engineering. sciences. A. A. Gusev, V. V. Solomonov, V. M. Samoilenko; engineers V.F.Gulyaeva, T.N.Malkina); TsNIIEP them. Mezentseva (candidate of technical sciences L. M. Schmidt, engineer P. Ye. Zhavoronkov); TsNIIPromzdanny (Candidate of Engineering Sciences V.V. Fedorov, engineers E.S. Giller, V.V. Sipin) and VNIIPO (Doctor of Technical Sciences, Prof. A.I. P. Bushev, S. V. Davydov, V. G. Olimpiev, N. F. Gavrikov; engineers V. 3. Volokhatykh, Yu. A. Grinchik, N. P. Savkin, A. N. Sorokin, V. S. Kharitonov, L. V. Sheinina, V. I. Shchelkunov). Sec. 3 developed by TsNIISK them. Kucherenko (Doctor of Technical Sciences, Prof. I. G. Romanenkov, Candidate of Chemical Sciences N. V. Kovyrshina, Engineer V. G. Gonchar) and the Institute of Mining Mechanics of the Academy of Sciences of Georgia. SSR (Candidate of Technical Sciences G. S. Abashidze, engineers L. I. Mirashvili, L. V. Gurchumelia).

In the development of the Manual, materials from TsNIIEP of housing and TsNIIEP of educational buildings of Gosgrazhdanstroy, MNIT Ministry of Railways of the USSR, VNIISTROM and NIPIsilikatobeton of the USSR Ministry of Industry and Construction were used.

The text of SNiP II-2-80 used in the Guide is typed in bold. Its items are double numbered, in parentheses the SNiP numbering is given.

In cases where the information given in the Manual is insufficient to establish the appropriate indicators of structures and materials, you should contact TsNIISK nm for advice and applications for conducting fire tests. Kucherenko or NIIZhB Gosstroy of the USSR. The basis for establishing these indicators can also be the results of tests carried out in accordance with the standards and methods approved or agreed by the USSR State Construction Committee.

Comments and suggestions on the Manual, please send to the address: Moscow, 109389, 2nd Institutskaya st., 6, TsNIISK im. V.A.Kucherenko.

1. GENERAL PROVISIONS

1.1. The manual is compiled to help design, construction? organizations and fire protection authorities in order to reduce the cost of time, labor and materials to establish the limits of fire resistance of building structures, the limits of the spread of fire along them and the flammability groups of materials, standardized by SNiP 11-2-80.

1.3. (2.4). According to their flammability, building materials are divided into three groups: non-combustible, hardly combustible and combustible.

2. BUILDING CONSTRUCTIONS.

FIRE RESISTANCE LIMITS AND FIRE SPREAD LIMITS

The limit of spread of fire on building structures is determined according to the method given in Appendix. 2.

FIRE RESISTANCE LIMIT

designs); in terms of thermal insulation capacity - an increase in temperature on an unheated surface by an average of more than 160 ° С or at any point on this surface by more than 190 ° С in comparison with the temperature of the structure before testing, or more than 220 ° С regardless of the temperature of the structure before testing; in terms of density - the formation of through cracks or through holes in structures through which combustion products or flame penetrate; for structures protected by fire retardant coatings and tested without loads, the limiting state will be the achievement of the critical temperature of the material of the structure.

For exterior walls, coverings, beams, trusses, columns and pillars, the limiting state is only the loss of the bearing capacity of structures and assemblies.

2.4. The limiting states of structures in terms of fire resistance, indicated in clause 2.3, in what follows, for brevity, will be called, respectively, l t II, III and IV the limiting states of a structure in terms of fire resistance.

2.5. The limits of fire resistance of structures can also be determined by calculation. In these cases, the tests are allowed not to be carried out.

The determination of the fire resistance limits by calculation should be carried out according to the methods approved by the Glavtekhnormirovanie Gosstroy of the USSR.

2.6. For an approximate assessment of the fire resistance of structures in their development and design, the following provisions can be followed:

c) the limits of fire resistance of enclosing structures with asymmetry

d) an increase in the moisture content of structures contributes to a decrease in the heating rate and an increase in fire resistance, with the exception of those cases when an increase in moisture increases the likelihood of a sudden brittle destruction of the material or the appearance of local gouges, this phenomenon is especially dangerous for concrete and asbestos-cement structures;

f) the fire resistance limit of the structure is the higher, the smaller is the ratio of the heated perimeter of the section of its elements to their area;

To assess the limit of fire resistance of structures on the basis of the above provisions, it is necessary to have sufficient information about the limits of fire resistance of structures similar to those considered in shape, used materials and design, as well as information about the basic laws of their behavior in case of fire or fire tests. *

FIRE SPREAD LIMIT

2.9. Damage is defined as visually detectable charring or burnout of materials and melting of thermoplastic materials.

For the limit of fire propagation, the maximum size of damage (cm) is taken, determined by the test methodology set forth in Appendix. 2 to SNiP II-2-8G.

2.10. Structures made with the use of combustible and hardly combustible materials, as a rule, without finishing and cladding, are tested for the spread of fire.

Structures made only of non-combustible materials should be considered non-spreading fire (the limit of fire spreading along them should be taken equal to zero).

If, during the test for the spread of fire, damage to structures in the control area is not more than 5 cm, it should also be considered non-spreading fire.

2L For a preliminary estimate of the limit of spread of fire, the following provisions may be used:

CONCRETE AND REINFORCED CONCRETE STRUCTURES

2.15. The distance to the axis of the reinforcement and the minimum dimensions of the elements to ensure the required limit of fire resistance of structures depend on the type of concrete. Lightweight concretes have a thermal conductivity of 10-20%, and concretes with coarse carbonate aggregate are 5-10% less than heavy concretes with silicate aggregates. In this regard, the distance to the axis of the reinforcement for a structure made of lightweight concrete or heavy concrete with a carbonate filler can be taken less than for structures made of heavy concrete with a silicate aggregate with the same fire resistance limit for structures made of these concretes.

2.16. During a fire, a protective layer of concrete protects the reinforcement from rapid heating and reaching its critical temperature, at which the fire resistance of the structure is reached.

Table 2, 4-8 show the distances from the heated surface to the axis of the reinforcement (Fig. 1 and 2).

Rice. 1. Distances to the axis of the reinforcement Fig. 2. Average distance to the axis

fittings

In cases where reinforcement is located at different levels, the average

the distance to the axis of the reinforcement a must be determined taking into account the areas of the reinforcement (L b L 2, ..., L p) and the corresponding distances to the axes (a b a-2,> Rn), measured from the nearest from the heating

myh (bottom or side) surfaces of the element, according to the formula

A \ H \ \ A ^

Ajfli -f- A ^ cl ^ ~ b. ... N ~ L p Dp __ 1_

P1 + L2 + P3. ... + Lp 2 Lg

2.17. All steels reduce tensile or compressive resistance

1 Additional heat-insulating coatings can be performed in accordance with the "Recommendations for the use of fire-retardant coatings for metal structures" - M .; Stroyizdat, 1984.

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